The ShakeAlert Earthquake Early Warning System and the Federal Role
Changes from June 1, 2022 to April 24, 2025
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The ShakeAlert Earthquake Early Warning System and the Federal Role
Updated April 24, 2025 (R47121) Jump to Main Text of ReportContents
- Introduction
- Primer on Earthquake Early Warnings
- Federal Role in Identifying Earthquake Risks
- Background and Authority to Issue Earthquake Early Warnings
- The ShakeAlert System
- Earthquake-Sensing Network
- Data Processing, Analysis, and Alert Message Generation
- Communication of Earthquake Early Warnings
- FEMA Communication Pathways
- Other Communication Pathways
- Performance: Speed and Accuracy of Earthquake Detection and Alert Messaging
- Communication Pathways Performance: Delivery of Earthquake Early Warnings
- Public Reaction to Earthquake Early Warnings
- ShakeAlert Administration
- Responsibility and Governance
- Funding Trends and Estimated Future Costs for ShakeAlert
- USGS ShakeAlert Funding
- Other ShakeAlert Funding
- Comparison of ShakeAlert with Other Earthquake Early Warning Systems
- Seismic- and Geodetic-Based Network
- Fixed or Crowd-Sourced Cell Phone Network
- Future of ShakeAlert and EEW Science and Technology
- Issues for Congress
Figures
- Figure 1. Plate Tectonics
- Figure 2. Major Faults on the West Coast of Part of North America
- Figure 3. USGS Seismic Hazard Model, 2023
- Figure 4. FEMA Distribution of Average Annualized Earthquake Loss by Region
- Figure 5. Schematic of the ShakeAlert System
- Figure 6. ShakeAlert System from Detection to Protection
- Figure 7. Seismic Stations Contributing to ShakeAlert as of December 2024
- Figure 8. Geodetic Stations Contributing to ShakeAlert as of December 2024
- Figure 9. ShakeAlert Message Generation and Alert Delivery
- Figure 10. Alert Communication Pathways and Minimum Thresholds
- Figure 11. FEMA Communication Pathways
- Figure 12. Timeline of Public EEW by Country or Region and Population Size Alerted
- Figure A-1. Earthquake Magnitude and Energy Released
- Figure A-2. Earthquake Hazards
Tables
- Table 1. Examples of Protective Actions That May Be Taken After Receiving an Earthquake Early Warning
- Table 2. ShakeAlert Nonfederal Partners
- Table 3. Regional Networks That Contribute to ShakeAlert
- Table 4. ShakeAlert License to Operate Partners, as of 2024
- Table 5. USGS Enacted Appropriations for EEW Activities and ShakeAlert
- Table 6. Nonfederal Funding for the ShakeAlert System
- Table A-1. Modified Mercalli Intensity Scale
Summary
Portions of all 50 states, as well as U.S. territories and the District of Columbia, arehomeless; damaged more than 40,000 buildings; and caused an estimated $13-$20 homeless; damaged more than 40,000 buildings; and caused an estimated $13-$20
and injuries, as well as damage to structures and operations). EEW refers to sending a warning to areas that may and injuries, as well as damage to structures and operations). EEW refers to sending a warning to areas that may
experience the highest intensity shaking; the EEW is sent after an earthquake is detected, but before damaging experience the highest intensity shaking; the EEW is sent after an earthquake is detected, but before damaging
ground-shaking reaches the ground-shaking reaches the
institutions and individuals to take protective actions (e.g., an institution can automatically stop a train to prevent institutions and individuals to take protective actions (e.g., an institution can automatically stop a train to prevent
derailment or an individual can avoid getting into an elevator to avoid harm).derailment or an individual can avoid getting into an elevator to avoid harm).
suddenly, and mass notification to high-risk areas must occur within seconds of earthquake detection to be suddenly, and mass notification to high-risk areas must occur within seconds of earthquake detection to be
effective. Congress directed the U.S. Geological Survey (USGS) to establish EEW capabilities in 2018 (42 U.S.C. effective. Congress directed the U.S. Geological Survey (USGS) to establish EEW capabilities in 2018 (42 U.S.C.
§7704(a)(2)(D)), as part of the reauthorization of the National Earthquake Hazards Reduction Program (NEHRP). §7704(a)(2)(D)), as part of the reauthorization of the National Earthquake Hazards Reduction Program (NEHRP).
Under the Stafford Act (42 U.S.C. §5132), the USGS has authority through the President to provide alerts about Under the Stafford Act (42 U.S.C. §5132), the USGS has authority through the President to provide alerts about
earthquakes using federal and other communication services to states and civilian populations in endangered earthquakes using federal and other communication services to states and civilian populations in endangered
areas. As Congress considers authorizations and appropriations for the programs that support EEWs, Congress may assess the performance and effectiveness of related federal authorities and mandates and EEW capabilities in the United States. Development of Earthquake Early Warning in the United States
An EEW system consists of the following components:An EEW system consists of the following components:
the ShakeAlert Earthquake Early Warning System (ShakeAlert) in California in 2019 and in Oregon and the ShakeAlert Earthquake Early Warning System (ShakeAlert) in California in 2019 and in Oregon and
Washington in 2021. ShakeAlert started as a prototype EEW system in 2012. Washington in 2021. ShakeAlert started as a prototype EEW system in 2012.
pathways pathways
cellular networks were cellular networks were generally fast (i.e., with delivery delays of less than five seconds), giving cell phone owners enough fast (i.e., with delivery delays of less than five seconds), giving cell phone owners enough
time in most cases to take protective actions before ground shaking arrived.time in most cases to take protective actions before ground shaking arrived.
Oversight and Policy Considerations
Congress may consider providing direction on policy priorities related to the authorities and mandates of the Congress may consider providing direction on policy priorities related to the authorities and mandates of the
NEHRP Reauthorization Act of 2018 (P.L. 115-307) and the Stafford Act to expand, contract, or change EEW NEHRP Reauthorization Act of 2018 (P.L. 115-307) and the Stafford Act to expand, contract, or change EEW
capabilities in the United States. Congress may seek additional information to assess ShakeAlertcapabilities in the United States. Congress may seek additional information to assess ShakeAlert
and effectiveness. In addition, Congress may seek more information about the ability of FEMA communication and effectiveness. In addition, Congress may seek more information about the ability of FEMA communication
pathways to provide rapid and targeted mass notification for earthquakes. Relatedly, Congress may explore policy pathways to provide rapid and targeted mass notification for earthquakes. Relatedly, Congress may explore policy
options for improving FEMA communication pathways.options for improving FEMA communication pathways.
consider a range of options to do so, such as consider a range of options to do so, such as
Introduction
Earthquake early warning (EEW) is one way to reduce fatalities and injuries, as well as damage to structures and operations, that may result from an earthquake. EEW refers to sending a warning to areas that may experience the highest intensity shaking; the EEW is sent after an earthquake is detected but before damaging ground-shaking reaches the area. An EEW received in tens of seconds to minutes before shaking allows institutions and individuals to take protective actions (e.g., an institution can automatically stop a train to prevent derailment or an individual can avoid getting into an elevator to avoid harm). The U.S. Geological Survey (USGS), with various federal, state, academic, and private partners, began public EEW on the West Coast via the ShakeAlert Earthquake Early Warning System (ShakeAlert) in California in 2019 and in Oregon and Washington in 2021.1 There is interest in expanding ShakeAlert to Alaska, Hawaii, and Nevada, as well as assessing and improving ShakeAlert's performance. ShakeAlert sent 41 public alerts for earthquakes that caused light shaking and little damage between October 17, 2019, and September 1, 2023.2 EEWs sent via the Federal Emergency Management Agency (FEMA) communication pathways may be delayed by more than five seconds. EEWs sent via cell phone applications over Wi-Fi or cellular networks were generally fast (i.e., with delivery delays of less than five seconds), giving cell phone owners enough time in most cases to take protective actions before ground shaking arrived.As Congress considers authorizations and appropriations for the programs that support earthquake-related EEWs and ShakeAlert specifically, Congress may assess the performance and effectiveness of related federal authorities and mandates and EEW capabilities in the United States. Congress may assess the ability of existing communication pathways to provide rapid and targeted mass notification for earthquakes, and it may consider whether (and, if so, how) to improve these communication pathways. This report focuses on ShakeAlert and concludes with a discussion of potential issues for Congress regarding funding, policy, and priorities for EEW in the United States.
Primer on Earthquake Early Warnings An earthquake starts by the sudden movement of rocky material under the Earth's surface along a s surface along aplane of weakness (i.e., a fault). Seismic waves radiate outward from the starting point of the plane of weakness (i.e., a fault). Seismic waves radiate outward from the starting point of the
earthquake, much like radial waves moving outward from a drop of waterearthquake, much like radial waves moving outward from a drop of water
shaking from the seismic waves and motion from the fault slip that reaches the surface may shaking from the seismic waves and motion from the fault slip that reaches the surface may
damage people and property and may cause commercial, government, educational, social, damage people and property and may cause commercial, government, educational, social,
cultural, and economic losses. An earthquake cultural, and economic losses. An earthquake
and many governments establish and direct programs to understand earthquake hazards and and many governments establish and direct programs to understand earthquake hazards and
reduce earthquake risks to protect their communities.reduce earthquake risks to protect their communities.
funding for earthquake research to understand earthquake hazards, reduce earthquake risks, funding for earthquake research to understand earthquake hazards, reduce earthquake risks,
understand geologic structure below the surface, detect underground nuclear explosions, and for understand geologic structure below the surface, detect underground nuclear explosions, and for
other purposes.other purposes.
within seconds to minutes of receiving the warning.within seconds to minutes of receiving the warning.
earthquake-sensing network, data communications, data analysis, alert formulation, and an alert earthquake-sensing network, data communications, data analysis, alert formulation, and an alert
message distribution system. The earthquake-sensing network consists of an array of earthquake-message distribution system. The earthquake-sensing network consists of an array of earthquake-
sensing stations that continuously and autonomously monitor for earthquakes near faults. A sensing stations that continuously and autonomously monitor for earthquakes near faults. A
station consists of seismic and/or geodetic instruments, power supplies, telemetry, and structures station consists of seismic and/or geodetic instruments, power supplies, telemetry, and structures
to protect the instruments and electronics.to protect the instruments and electronics.
ground motion accelerometers or or strong ground motion instruments), detect and measure the ), detect and measure the
properties of earthquakes, especially the arrival of the first seismic waves and the earliest properties of earthquakes, especially the arrival of the first seismic waves and the earliest
on the ground measure ground displacement and peak ground acceleration caused by an on the ground measure ground displacement and peak ground acceleration caused by an
earthquake using a Global Navigation Satellite Systems (GNSS) receiver.earthquake using a Global Navigation Satellite Systems (GNSS) receiver.
recorded by geodetic instruments do not go off scale, regardless of the earthquakerecorded by geodetic instruments do not go off scale, regardless of the earthquake
location. Geodetic data location. Geodetic data may provide critical real-time information about ground motions to estimate provide critical real-time information about ground motions to estimate
so institutions and individuals have enough time to take protective action before intense ground so institutions and individuals have enough time to take protective action before intense ground
shaking arrives at their locations. EEW does not work for individuals and institutions shaking arrives at their locations. EEW does not work for individuals and institutions
to an earthquake because there is not enough time to detect the event and communicate a warning to an earthquake because there is not enough time to detect the event and communicate a warning
before intense ground shaking reaches nearby locations.before intense ground shaking reaches nearby locations.
system.system.
they happen, where they occur, how frequently they may occur, and how much of a risk they may they happen, where they occur, how frequently they may occur, and how much of a risk they may
pose to society. Some earthquakes produce earthquake hazards, such as ground shaking and pose to society. Some earthquakes produce earthquake hazards, such as ground shaking and
ground displacement; these hazards can cause damage and, in rare but significant cases, can cause ground displacement; these hazards can cause damage and, in rare but significant cases, can cause
catastrophic damage. Earthquakes cannot be predicted, so to prepare and respond to the sudden catastrophic damage. Earthquakes cannot be predicted, so to prepare and respond to the sudden
onset of a potentially catastrophic event, an EEW system needs to rapidly and accurately detect onset of a potentially catastrophic event, an EEW system needs to rapidly and accurately detect
the starting time and initial location of a damaging earthquake and estimate where the most the starting time and initial location of a damaging earthquake and estimate where the most
intense ground shaking may occur.intense ground shaking may occur.
(Earthquake Hazards Reduction Act; P.L. 95-124, 42 U.S.C. §7704) as a coordinated federal (Earthquake Hazards Reduction Act; P.L. 95-124, 42 U.S.C. §7704) as a coordinated federal
program focused on understanding earthquake hazards and reducing earthquake risks, including program focused on understanding earthquake hazards and reducing earthquake risks, including
by warning the public about earthquakes. Four agencies—the by warning the public about earthquakes. Four agencies—the
USGS, National Science Foundation (NSF), National Science Foundation (NSF),
National Institute of Standards and Technology (NIST)—constitute the program. Congress National Institute of Standards and Technology (NIST)—constitute the program. Congress
appropriated $appropriated $
develop an EEW capability (P.L. 115-307, 42 U.S.C. §7704(a)(2)(D)). The first operational EEW develop an EEW capability (P.L. 115-307, 42 U.S.C. §7704(a)(2)(D)). The first operational EEW
system in the United States, ShakeAlert on the West Coast, provides warnings to individuals and system in the United States, ShakeAlert on the West Coast, provides warnings to individuals and
institutions about intense ground shaking reaching their location in a matter of seconds to minutes institutions about intense ground shaking reaching their location in a matter of seconds to minutes
from an earthquake detection. ShakeAlert consists of an earthquake-sensing network of seismic from an earthquake detection. ShakeAlert consists of an earthquake-sensing network of seismic
and geodetic stations that detect an earthquake and data processing centers with algorithms and and geodetic stations that detect an earthquake and data processing centers with algorithms and
decisionmaking software that prepare alert messages. The alert messages contain the estimated decisionmaking software that prepare alert messages. The alert messages contain the estimated
earthquake location, earthquake magnitude, and the areas that may receive intense ground earthquake location, earthquake magnitude, and the areas that may receive intense ground
shaking in an estimated time period. ShakeAlert has been developed and tested and is now shaking in an estimated time period. ShakeAlert has been developed and tested and is now
operated, maintained, and improved based on past and current earthquake research and operated, maintained, and improved based on past and current earthquake research and
earthquake-sensing technology development. ShakeAlert earthquake-sensing technology development. ShakeAlert
other federal and nonfederal partners. ShakeAlert is funded by federal and nonfederal partners. other federal and nonfederal partners. ShakeAlert is funded by federal and nonfederal partners.
The system does not eliminate all risks but is one component of NEHRPThe system does not eliminate all risks but is one component of NEHRP
earthquake risks. Federal Role in Identifying Earthquake Risks
The USGS and FEMA assess earthquake hazards and identify earthquake risks in the United The USGS and FEMA assess earthquake hazards and identify earthquake risks in the United
States, as directed and funded by NEHRP.States, as directed and funded by NEHRP.16 An effective EEW system to reduce risks may be An effective EEW system to reduce risks may be
established where the earthquake risks are the highest. The USGS Earthquake Hazards Program established where the earthquake risks are the highest. The USGS Earthquake Hazards Program
(EHP) conducts earthquake research; studies and catalogs earthquake activity; maps faults; (EHP) conducts earthquake research; studies and catalogs earthquake activity; maps faults;
assesses earthquake hazards; and prepares earthquake notifications that include estimates of assesses earthquake hazards; and prepares earthquake notifications that include estimates of
earthquake hazards and damage, as well as information about an earthquake and its fault.earthquake hazards and damage, as well as information about an earthquake and its fault.
Catalog (ComCat), an archive of earthquakes in the United States and significant earthquakes Catalog (ComCat), an archive of earthquakes in the United States and significant earthquakes
globally.globally.
risks from each event, are a public resource. These summaries are posted as soon as possible after risks from each event, are a public resource. These summaries are posted as soon as possible after
an event and may be updated over time to provide the most accurate information about the an event and may be updated over time to provide the most accurate information about the
earthquake and its impact. The ComCat data are used to test EEW systems using past earthquake earthquake and its impact. The ComCat data are used to test EEW systems using past earthquake
scenarios, and ComCat posts summaries of ShakeAlert performance for alerts for earthquakes in scenarios, and ComCat posts summaries of ShakeAlert performance for alerts for earthquakes in
California, Oregon, and Washington.California, Oregon, and Washington.
and institutions that sign up to receive notifications.and institutions that sign up to receive notifications.
for an event as soon as information is available. Earthquake notification information is useful to for an event as soon as information is available. Earthquake notification information is useful to
emergency responders and post-earthquake recovery, as it identifies regions that may be emergency responders and post-earthquake recovery, as it identifies regions that may be
earthquake hazards. Catalogs of past earthquakes identify active faults, how the faults are earthquake hazards. Catalogs of past earthquakes identify active faults, how the faults are
changing with time, and where earthquakes may be likely to occur in the future. Past earthquake changing with time, and where earthquakes may be likely to occur in the future. Past earthquake
assessment, current earthquake monitoring, and research helps the USGS identify and map active assessment, current earthquake monitoring, and research helps the USGS identify and map active
faults and their associated earthquake hazards.faults and their associated earthquake hazards.
These areas are referred to as These areas are referred to as plate tectonic boundaries (Figure 1). Most of the largest magnitude . Most of the largest magnitude
and most damaging earthquakes in the geologic record occur at collisional boundaries between and most damaging earthquakes in the geologic record occur at collisional boundaries between
major tectonic plates. Two major types of collisional boundaries, subduction zones and strike-slip major tectonic plates. Two major types of collisional boundaries, subduction zones and strike-slip
zones, are of most concern to society because of the potential for damaging earthquakes.zones, are of most concern to society because of the potential for damaging earthquakes.
subduction zones occur offshore, below the water surface. In some cases, when an earthquake subduction zones occur offshore, below the water surface. In some cases, when an earthquake
occurs on a submarine subduction zone, the earthquake may trigger a tsunami occurs on a submarine subduction zone, the earthquake may trigger a tsunami
(Figure 1).
Figure 1. Plate Tectonics Source: USGS, USGS,
. Notes: Divergent boundaries (red lines) denote rift zones or primarily normal fault type of motion (plates are Divergent boundaries (red lines) denote rift zones or primarily normal fault type of motion (plates are
types of motion (plates are pushing together). Transform boundaries (blue lines) denote primarily laterally sliding types of motion (plates are pushing together). Transform boundaries (blue lines) denote primarily laterally sliding
plate boundaries or primarily strike-slip fault type of motion (plates are sliding past each other). The lines plate boundaries or primarily strike-slip fault type of motion (plates are sliding past each other). The lines
generalize and approximate the surface trace of more complicated geologic structures that consist of many fault generalize and approximate the surface trace of more complicated geologic structures that consist of many fault
branches, and branches, and
colored lines in the blue ocean water on this figure). Major plate colored lines in the blue ocean water on this figure). Major plate
(primarily strike-slip faulting) in California, the Great African Rift System (primarily normal faulting) and the (primarily strike-slip faulting) in California, the Great African Rift System (primarily normal faulting) and the
continent-continent continent-continent
faulting), creating the highest mountain range, the Himalayas.faulting), creating the highest mountain range, the Himalayas.
its territories are three different subduction zones, offshore of Alaska, the Pacific Northwest, and its territories are three different subduction zones, offshore of Alaska, the Pacific Northwest, and
Puerto Rico, and one strike-slip zone in California Puerto Rico, and one strike-slip zone in California (Figure 1). The most active (i.e., have the . The most active (i.e., have the
most frequent earthquakes) and damaging subduction zones (i.e., have the potential to have large most frequent earthquakes) and damaging subduction zones (i.e., have the potential to have large
magnitude [M7.0+] events and may trigger tsunamis) that directly impact coastal populations and magnitude [M7.0+] events and may trigger tsunamis) that directly impact coastal populations and
California through the state of California and then offshore just north of San California through the state of California and then offshore just north of San
2), is a strike-slip fault system created by two tectonic plates that are sliding against each other. , is a strike-slip fault system created by two tectonic plates that are sliding against each other.
The Pacific Plate is sliding against the North America Plate, producing a wide area of multiple The Pacific Plate is sliding against the North America Plate, producing a wide area of multiple
faults, including the San Andreas Fault. The collision of the plates produces many earthquakes, faults, including the San Andreas Fault. The collision of the plates produces many earthquakes,
primarily in the shallow crust and because these earthquakes are shallow, they may produce primarily in the shallow crust and because these earthquakes are shallow, they may produce
intense ground shaking and/or ground displacement at the surface. Because the faults are intense ground shaking and/or ground displacement at the surface. Because the faults are
extensive, an earthquake may slip over a large area and may produce large magnitude earthquakes extensive, an earthquake may slip over a large area and may produce large magnitude earthquakes
(M7.0+). California is a high earthquake risk state because of the many shallow earthquakes on (M7.0+). California is a high earthquake risk state because of the many shallow earthquakes on
active and extensive faults near populated areas or areas with critical infrastructure (e.g., active and extensive faults near populated areas or areas with critical infrastructure (e.g.,
pipelines, roads, bridges, dams, and aqueducts).
Figure 2. Major Faults on the West Coast of Part of North America Source: U.S. Geological Survey, U.S. Geological Survey,
. Notes: The West Coast of the United States is vulnerable to earthquakes because of the major The West Coast of the United States is vulnerable to earthquakes because of the major
collisions between tectonic plates. California is most vulnerable to earthquakes on the San Andreas Fault and many parallel between tectonic plates. California is most vulnerable to earthquakes on the San Andreas Fault and many parallel
and branching faults (these other faults are not shown on the figure). The San Andreas Fault is caused by the and branching faults (these other faults are not shown on the figure). The San Andreas Fault is caused by the
noted by the red arrows on the figure). The San Andreas Fault continues into Mexico, causing earthquake risks noted by the red arrows on the figure). The San Andreas Fault continues into Mexico, causing earthquake risks
for Mexico. Northern California, Oregon, Washington, and British Columbia, Canada, are susceptible to for Mexico. Northern California, Oregon, Washington, and British Columbia, Canada, are susceptible to
earthquakes on the Cascadia Subduction Zone (labeled Subduction Zone on the figure). The Cascadia earthquakes on the Cascadia Subduction Zone (labeled Subduction Zone on the figure). The Cascadia
Subduction Zone is caused by the Juan de Fuca Plate (not labeled on the figure but located between the labeled Subduction Zone is caused by the Juan de Fuca Plate (not labeled on the figure but located between the labeled
subduction zone and the Juan De Fuca ridge) subduction zone and the Juan De Fuca ridge)
Not shown are other major collisional boundaries impacting Alaska and parts of Canada, Mexico, Central America, and the Caribbean in North America.
Subduction Slab Model maps subduction zones around the world.Subduction Slab Model maps subduction zones around the world.
regularly updates its Seismic Hazard regularly updates its Seismic Hazard
intensity of VI, felt by all with slight damage to structures, on the Modified Mercalli Intensity intensity of VI, felt by all with slight damage to structures, on the Modified Mercalli Intensity
plate boundariesplate boundaries
.30
Figure 3. USGS Seismic Hazard Model, 2023
Source: Mark D. Peterson et al., "The 2023 US 50-State National Seismic Hazard Model: Overview and Implications," Earthquake Spectra, vol. 40, no. 1 (2024), DOI: 10.1177/87552930231215428.
Notes: Alaska, California, Oregon, and Washington have high earthquake probabilities (>60%) because they are Alaska, California, Oregon, and Washington have high earthquake probabilities (>60%) because they are
near major plate tectonic near major plate tectonic
volcanoes. The Commonwealth of Puerto Rico has high earthquake probabilities because it is near a volcanoes. The Commonwealth of Puerto Rico has high earthquake probabilities because it is near a
collisional plate boundary. Idaho, Montana, Utah, and Wyoming have medium to high earthquake probabilities (20%-95%) plate boundary. Idaho, Montana, Utah, and Wyoming have medium to high earthquake probabilities (20%-95%)
because of the Yellowstone volcano and the Intermountain Seismic Belt (including the Wasatch Fault) between because of the Yellowstone volcano and the Intermountain Seismic Belt (including the Wasatch Fault) between
the Basin and Range Province and the Rocky Mountains. The New Madrid seismic zone, at the intersection of the Basin and Range Province and the Rocky Mountains. The New Madrid seismic zone, at the intersection of
Arkansas, Arkansas,
medium earthquake probabilities (20%-60%) because of past large-magnitude (M7.0+) earthquakes that occurred medium earthquake probabilities (20%-60%) because of past large-magnitude (M7.0+) earthquakes that occurred
in the early to late 1800s. Little is known about the faults that caused these large earthquakes, because there is in the early to late 1800s. Little is known about the faults that caused these large earthquakes, because there is
not enough information to decipher the structure below the surface. Other states with low earthquake not enough information to decipher the structure below the surface. Other states with low earthquake
probabilities (2%-20%) are vulnerable to earthquakes. Earthquakes cannot be predicted nor can the potential for probabilities (2%-20%) are vulnerable to earthquakes. Earthquakes cannot be predicted nor can the potential for
an earthquake to occur in areas with some seismic history be ruled out. an earthquake to occur in areas with some seismic history be ruled out.
States. FEMA estimates annualized building loss due to potential earthquake hazards using a States. FEMA estimates annualized building loss due to potential earthquake hazards using a
hazard model called Hazus hazard model called Hazus (Figure 4)
California, Oregon, and Washington face the greatest risks for the largest annualized building California, Oregon, and Washington face the greatest risks for the largest annualized building
losses based on the Hazus model. Other potential losses that are harder to estimate include losses based on the Hazus model. Other potential losses that are harder to estimate include
damage to roads, bridges, utilities, dams and reservoirs, power plants, mines and quarries, and damage to roads, bridges, utilities, dams and reservoirs, power plants, mines and quarries, and
other structures, in addition to the disruption of commercial, education, government, and other structures, in addition to the disruption of commercial, education, government, and
nongovernment operations. In nongovernment operations. In
national building stock building stock
AEL due to the earthquake frequency, built environment density, and population size in these AEL due to the earthquake frequency, built environment density, and population size in these
states.states.
the risks for different hazards, including earthquakes, in each county in every state.the risks for different hazards, including earthquakes, in each county in every state.
index includes expected annualized losses, social impacts, and community resilience.index includes expected annualized losses, social impacts, and community resilience.
to this index, California, Oregon, and Washington have the highest risk index for earthquakes to this index, California, Oregon, and Washington have the highest risk index for earthquakes
across a larger area and a larger populationacross a larger area and a larger population than other states.
Figure 4. FEMA Distribution of Average Annualized Earthquake Loss by Region
(estimates in 2022 dollars)
Sources: Figure and calculations from theAnnualized Earthquake Losses for the United States, ,
earthquake hazards is $earthquake hazards is $
other property, other infrastructure, business, government, and other losses. See FEMA, other property, other infrastructure, business, government, and other losses. See FEMA, Hazus
FEMA, FEMA,
Early Warnings
Since 1930, Congress has authorized programs and appropriated funds for earthquake research Since 1930, Congress has authorized programs and appropriated funds for earthquake research
(or seismology) to reduce earthquake risks.(or seismology) to reduce earthquake risks.
understanding of Earth processes, improved earthquake instrumentation, and earthquake risk understanding of Earth processes, improved earthquake instrumentation, and earthquake risk
reduction that has led to the development of EEW. Congress expanded earthquake research in the reduction that has led to the development of EEW. Congress expanded earthquake research in the
1960s; the expansion focused on detecting underground nuclear explosions using seismic 1960s; the expansion focused on detecting underground nuclear explosions using seismic
instruments and finding ways to reduce earthquake risks. Congress increased appropriations to instruments and finding ways to reduce earthquake risks. Congress increased appropriations to
almost $30 million (in 1959-1961 dollars) annually between 1959 and 1961 for the Department of almost $30 million (in 1959-1961 dollars) annually between 1959 and 1961 for the Department of
underground nuclear explosions and to support cooperation among nations to detect nuclear underground nuclear explosions and to support cooperation among nations to detect nuclear
accelerated the sharing and standardization of seismic technology and data throughout the accelerated the sharing and standardization of seismic technology and data throughout the
world.world.
potential for earthquake prediction potential for earthquake prediction
earthquake on the Aleutian Arc Subduction Zone, the largest event ever recorded in the United earthquake on the Aleutian Arc Subduction Zone, the largest event ever recorded in the United
States, caused 9 fatalities, many injuries, and extensive damage in Alaska and generated a States, caused 9 fatalities, many injuries, and extensive damage in Alaska and generated a
tsunami that caused 122 fatalities, many injuries, and damage in Alaska, Hawaii, Washington, tsunami that caused 122 fatalities, many injuries, and damage in Alaska, Hawaii, Washington,
Oregon, and California.Oregon, and California.
injuries, and extensive damage (including damage to the lower Van Norman Dam) in Los Angeles injuries, and extensive damage (including damage to the lower Van Norman Dam) in Los Angeles
County.County.
Haicheng earthquake struck on February 4, 1975, saving lives. This was considered a successful Haicheng earthquake struck on February 4, 1975, saving lives. This was considered a successful
earthquake earthquake
such an earthquake prediction could not be repeated. There are no precursor physical changes that such an earthquake prediction could not be repeated. There are no precursor physical changes that
could be used to predict earthquakes, although research continues to try to understand what may could be used to predict earthquakes, although research continues to try to understand what may
cause an earthquake and whether any physical changes may precede an earthquake.cause an earthquake and whether any physical changes may precede an earthquake.
workshops from other groups, called for a coordinated federal program to research (1) earthquake workshops from other groups, called for a coordinated federal program to research (1) earthquake
hazards and risk assessments, (2) earthquake prediction and warning of an hazards and risk assessments, (2) earthquake prediction and warning of an imminent earthquake, earthquake,
and/or (3) earthquake-resistant engineering.and/or (3) earthquake-resistant engineering.
Act of 1977 (P.L. 95-124), which codified a coordinated program to reduce risks by considering Act of 1977 (P.L. 95-124), which codified a coordinated program to reduce risks by considering
these three research directions. It also authorized appropriations for the programthese three research directions. It also authorized appropriations for the program
NSF.NSF.
accompanying the 1977 act as follows: accompanying the 1977 act as follows:
prediction, in definite or probabilistic terms, of the time, place, and magnitude of an earthquake, prediction, in definite or probabilistic terms, of the time, place, and magnitude of an earthquake,
whereas an earthquake warning means a recommendation that normal life routines should be whereas an earthquake warning means a recommendation that normal life routines should be
current understanding of Earth processes. Therefore, NEHRPcurrent understanding of Earth processes. Therefore, NEHRP
in the 1980s.in the 1980s.
prototype in the 1997 reauthorization of NEHRP (P.L. 105-47). An automatic seismic hazard prototype in the 1997 reauthorization of NEHRP (P.L. 105-47). An automatic seismic hazard
warning system warns warning system warns
detected and that damaging shaking is coming to the operationsdetected and that damaging shaking is coming to the operations
the operations to take automated actions, such as stopping a train, to reduce risks.the operations to take automated actions, such as stopping a train, to reduce risks.
requiring the USGS to develop procedures for making earthquake predictions and replaced it with requiring the USGS to develop procedures for making earthquake predictions and replaced it with
language requiring NEHRP to develop procedures to issue EEWs. The language states that the language requiring NEHRP to develop procedures to issue EEWs. The language states that the
USGS should USGS should
earthquake early warning capabilities.earthquake early warning capabilities.
earthquake, to issue an alert and a warning, when necessary and feasible, to FEMA, NIST, and earthquake, to issue an alert and a warning, when necessary and feasible, to FEMA, NIST, and
state and local officials.state and local officials.
in the Disaster Relief Act of 1974 (P.L. 93-288, 42 U.S.C. §5132), which was reauthorized and in the Disaster Relief Act of 1974 (P.L. 93-288, 42 U.S.C. §5132), which was reauthorized and
renamed the Robert T. Stafford Disaster Relief and Emergency Assistance Act in 1987 (Stafford renamed the Robert T. Stafford Disaster Relief and Emergency Assistance Act in 1987 (Stafford
Act; P.L. 100-707). Congress directed the President (1) to ensure agencies are able to issue Act; P.L. 100-707). Congress directed the President (1) to ensure agencies are able to issue
disaster warnings to state and local governments and to use federal agencies to assist states and disaster warnings to state and local governments and to use federal agencies to assist states and
local officials with disaster warnings,local officials with disaster warnings,
provide disaster warnings to states and the civilian population in endangered areas, and (3) to provide disaster warnings to states and the civilian population in endangered areas, and (3) to
cooperate with private or commercial communication systems to provide disaster warnings to cooperate with private or commercial communication systems to provide disaster warnings to
states and the civilian population in endangered areas. Congress authorized the President to direct states and the civilian population in endangered areas. Congress authorized the President to direct
the USGS to provide warnings about earthquakes using civilian defense warning systems and to the USGS to provide warnings about earthquakes using civilian defense warning systems and to
enter into agreements to use private or commercial communication systems to provide disaster enter into agreements to use private or commercial communication systems to provide disaster
warnings to states and civilian populations in endangered areas.warnings to states and civilian populations in endangered areas.
earthquake early warnings in the Stafford Act. The USGS calls its earthquake early warnings in the Stafford Act. The USGS calls its
they are not earthquake predictions or forecasts but are based on detecting the start of an they are not earthquake predictions or forecasts but are based on detecting the start of an
earthquake and then providing a warning within tens of seconds. In contrast, most severe weather earthquake and then providing a warning within tens of seconds. In contrast, most severe weather
warnings provide hours to days for preparation and protective actions.warnings provide hours to days for preparation and protective actions.
45 The ShakeAlert System
ShakeAlert is the first public EEW system operating in the United States.ShakeAlert is the first public EEW system operating in the United States.
uses FEMA or other communication pathways to provide alerts to individuals and institutions. uses FEMA or other communication pathways to provide alerts to individuals and institutions.
ShakeAlert began sending earthquake alerts to communication providers for EEW broadcasts to ShakeAlert began sending earthquake alerts to communication providers for EEW broadcasts to
the public in California in October 2019, in Oregon in March 2021, and in Washington in May the public in California in October 2019, in Oregon in March 2021, and in Washington in May
2021. ShakeAlert is available only in these three states. ShakeAlert consists of the following 2021. ShakeAlert is available only in these three states. ShakeAlert consists of the following
States were experimental and sent alerts to specific testers.States were experimental and sent alerts to specific testers.
United States started in California, because of the stateUnited States started in California, because of the state
California earthquake hazards, and the established seismic and geodetic networks that could California earthquake hazards, and the established seismic and geodetic networks that could
function as part of an earthquake-sensing network. Experimental EEW systems operated in function as part of an earthquake-sensing network. Experimental EEW systems operated in
Oakland and Southern California in 1989 and 1997, respectively, as short-term tests of EEW. A Oakland and Southern California in 1989 and 1997, respectively, as short-term tests of EEW. A
prototype EEW system called ShakeAlert began testing in California in 2012 and in the Pacific prototype EEW system called ShakeAlert began testing in California in 2012 and in the Pacific
Northwest in 2015. Congress appropriated funds for these activities primarily through the USGS Northwest in 2015. Congress appropriated funds for these activities primarily through the USGS
EHP and NSF research grants and cooperative agreements.EHP and NSF research grants and cooperative agreements.
point of an earthquake and sends earthquake-sensing instrument data to the data processing point of an earthquake and sends earthquake-sensing instrument data to the data processing
centers centers (Figure 5)
earthquake and prepare an alert before the slower, more damaging S-waves arrive at locations earthquake and prepare an alert before the slower, more damaging S-waves arrive at locations
further from the earthquakefurther from the earthquake
to the epicenter, because there is not enough time to complete the EEW process before the to the epicenter, because there is not enough time to complete the EEW process before the
shaking arrives. Data processing centers analyze the data and estimate the earthquakeshaking arrives. Data processing centers analyze the data and estimate the earthquake
and magnitude, as well as the area that may receive high-intensity ground shaking. The and magnitude, as well as the area that may receive high-intensity ground shaking. The
processing centers send the alert messages containing this information to communication processing centers send the alert messages containing this information to communication
providers.
Figure 5. Schematic of the ShakeAlert System Source: ShakeAlert, ShakeAlert,
States,States,
. Notes: Once an earthquake starts (star labeled Once an earthquake starts (star labeled epicenter and and fault on the figure), the ShakeAlert earthquake- on the figure), the ShakeAlert earthquake-
sensing network (sensing network (sensors on figure) detects the P-waves (yellow curve shows the P-wave radiating away from the on figure) detects the P-waves (yellow curve shows the P-wave radiating away from the
epicenter and arrow indicates the general direction of the waves) at sensors closest to the epicenter. The epicenter and arrow indicates the general direction of the waves) at sensors closest to the epicenter. The
sensors transmit these data to data processing centers (only one is shown on the figure, labeled sensors transmit these data to data processing centers (only one is shown on the figure, labeled Earthquake alert
center). The centers process the data and, if the earthquake may be damaging, prepare alert messages with ). The centers process the data and, if the earthquake may be damaging, prepare alert messages with
information about the earthquakeinformation about the earthquake
later-arriving, more damaging S-waves (red curve and arrow). Public and private communication pathways later-arriving, more damaging S-waves (red curve and arrow). Public and private communication pathways
convert the alert messages into convert the alert messages into
figure, the nearby city is in the path of the seismic waves; the goal is for everyone in the city to receive an EEW figure, the nearby city is in the path of the seismic waves; the goal is for everyone in the city to receive an EEW
before the S-waves reach the city and cause intense shaking.before the S-waves reach the city and cause intense shaking.
protective actions, which reduce earthquake risks and costs (e.g., for repairs or loss of operations) protective actions, which reduce earthquake risks and costs (e.g., for repairs or loss of operations)
by preventing damage to people and property by preventing damage to people and property (Figure 6)
actions based on ShakeAlert messages. These actions based on ShakeAlert messages. These
human intervention; the ShakeAlert messages are hardwired into critical operations (i.e., through human intervention; the ShakeAlert messages are hardwired into critical operations (i.e., through
machine-to-machine communications) and prompt automatic protective actions based on the machine-to-machine communications) and prompt automatic protective actions based on the
message details. Automated actions may include stopping or slowing trains, opening fire station message details. Automated actions may include stopping or slowing trains, opening fire station
doors, stopping elevators at a floor and opening elevator doors, preventing vehicles from entering doors, stopping elevators at a floor and opening elevator doors, preventing vehicles from entering
bridges or tunnels, and other actions.bridges or tunnels, and other actions.
risks by transmitting EEWs risks by transmitting EEWs (Figure 6). Emergency communication providers, such as FEMA . Emergency communication providers, such as FEMA
communication pathways or cell phone EEW applications (apps), receive the ShakeAlert communication pathways or cell phone EEW applications (apps), receive the ShakeAlert
messages and send EEWs to individuals in high-risk areas. These EEWs include the messages and send EEWs to individuals in high-risk areas. These EEWs include the
recommended protective action: Drop, Cover, and Hold On (DCHO).recommended protective action: Drop, Cover, and Hold On (DCHO).
to reduce risks.to reduce risks.
Figure 6. ShakeAlert System from Detection to Protection
Source: ShakeAlert, ShakeAlert,
. Table 1. Examples of Protective Actions That May Be Taken After Receiving an
Sector
Construction
construction sites.construction sites.
Management
General
Industrial
people away from hazardous industrial processes.people away from hazardous industrial processes.
Medical
Office
away from windows to interior/safer spaces.away from windows to interior/safer spaces.
Restaurants
Schools
Transportation
and slowing or stopping traffic by turning all traffic signals to red.and slowing or stopping traffic by turning all traffic signals to red.
Utilities
supplies, and moving field personnel into safer positions (i.e., places not exposed to power supplies, and moving field personnel into safer positions (i.e., places not exposed to power
lines or other hazardous conditions).lines or other hazardous conditions).
Vehicles
down.down.
Source: ShakeAlert, ShakeAlert,
responsible for the systemresponsible for the system
education and outreach education and outreach (Table 2). These partners include state agencies, universities, and . These partners include state agencies, universities, and
nonprofit organizations that operate NSF facilities. The USGS considers ShakeAlert to be part of nonprofit organizations that operate NSF facilities. The USGS considers ShakeAlert to be part of
the Advanced National Seismic System (ANSS) within the EHP.the Advanced National Seismic System (ANSS) within the EHP.
implementation plan for ShakeAlert in 2018, which summarized the science, technology, and implementation plan for ShakeAlert in 2018, which summarized the science, technology, and
implementation of ShakeAlert and how the USGS aims to improve the EEW system.implementation of ShakeAlert and how the USGS aims to improve the EEW system.
funds to these federal agencies specifically for ShakeAlert activities). FEMA provides funds to these federal agencies specifically for ShakeAlert activities). FEMA provides
communication pathways to deliver EEWs to the public and conducts earthquake risk communication pathways to deliver EEWs to the public and conducts earthquake risk
assessments. In addition, Congress authorized FEMA to award hazard mitigation grants to assessments. In addition, Congress authorized FEMA to award hazard mitigation grants to
improve ShakeAlertimprove ShakeAlert
Reform Act of 2018 (Division D of the Federal Aviation Administration Reauthorization Act of Reform Act of 2018 (Division D of the Federal Aviation Administration Reauthorization Act of
2018, P.L. 115-254) authorized FEMA to provide hazard mitigation assistance through the Hazard 2018, P.L. 115-254) authorized FEMA to provide hazard mitigation assistance through the Hazard
Mitigation Grant Program and the Building Resilient Infrastructure and Communities Program Mitigation Grant Program and the Building Resilient Infrastructure and Communities Program
for activities that reduce earthquake risk and build EEW capability.for activities that reduce earthquake risk and build EEW capability.
improvements to seismic and geodetic networks that are part of ShakeAlert and the purchase and improvements to seismic and geodetic networks that are part of ShakeAlert and the purchase and
installation of seismometers, GNSS receivers, and associated infrastructure (e.g., telemetry and installation of seismometers, GNSS receivers, and associated infrastructure (e.g., telemetry and
signal processing) that are part of the ShakeAlert system.signal processing) that are part of the ShakeAlert system.
by the Incorporated Research Institutions for Seismologyby the Incorporated Research Institutions for Seismology
Earthquake Center, operated by the University of Southern California).Earthquake Center, operated by the University of Southern California).
Aeronautics and Space Administration (NASA) supports the use of geodetic tools for earthquake Aeronautics and Space Administration (NASA) supports the use of geodetic tools for earthquake
and tsunami research and for hazards warning and mitigation.and tsunami research and for hazards warning and mitigation.
Institutional Partners Involved in ShakeAlert Research and Development, Operations and
EarthScope Consortium
Statewide California Earthquake Center (SCEC)
University of Nevada, Reno
University of Oregon (UO)
programs/earthquake-hazards/science/earthquake-early-warning-overview#partners; and ShakeAlert, programs/earthquake-hazards/science/earthquake-early-warning-overview#partners; and ShakeAlert,
https://www.shakealert.org/https://www.shakealert.org/
Technology in Zürich, in English). Earthquake-Sensing Network
The ShakeAlert earthquake-sensing network consists of 1,The ShakeAlert earthquake-sensing network consists of 1,
geodetic stations in California, Oregon, and geodetic stations in California, Oregon, and
of regional networks for research, hazard assessment, natural resource management, and other of regional networks for research, hazard assessment, natural resource management, and other
purposes purposes (Table 3). Some stations in these networks now serve an additional purpose: detecting . Some stations in these networks now serve an additional purpose: detecting
the start of an earthquake to provide EEW. The USGS and ShakeAlert partners aim to add more the start of an earthquake to provide EEW. The USGS and ShakeAlert partners aim to add more
seismic stations and upgrade more geodetic stations to improve earthquake detection on the West seismic stations and upgrade more geodetic stations to improve earthquake detection on the West
Coast.Coast.
Figure 7. Seismic Stations Contributing to ShakeAlert as of December 2024
Source: USGS, December 12, 2024. Modified by CRS. Map production supported by Esri, General Bathymetric Chart of the Oceans, Garmin, NatureVue, and National Geodetic Survey.
Notes: ShakeAlert's earthquake-sensing network consists of 1,553 operating seismic stations (blue dots) out of 1,675 planned stations (yellow squares). Planned stations would be either new stations or upgrades to existing stations.Figure 8. Geodetic Stations Contributing to ShakeAlert as of December 2024
Source: USGS, December 12, 2024. Modified by CRS. Map production supported by Esri, General Bathymetric Chart of the Oceans, Garmin, NatureVue, and National Geodetic Survey.
Note: ShakeAlert's earthquake-sensing network includes about 1,100 geodetic stations (blue dots).
to transmit data from seismic or geodetic stations to data processing centers.to transmit data from seismic or geodetic stations to data processing centers.
technology depends on the station location and technology and on the available telemetry technology depends on the station location and technology and on the available telemetry
systems. In California and Oregon, some stations use their respective state microwave telemetry systems. In California and Oregon, some stations use their respective state microwave telemetry
systems to transmit data. In California, the USGS connected the USGS microwave telemetry systems to transmit data. In California, the USGS connected the USGS microwave telemetry
systems between Northern and Southern California. The California Governorsystems between Northern and Southern California. The California Governor
Emergency Services (Cal OES) Public Safety Communications system and the University of Emergency Services (Cal OES) Public Safety Communications system and the University of
California, Berkeley, ShakeAlert data processing center are connected with a dedicated telemetry California, Berkeley, ShakeAlert data processing center are connected with a dedicated telemetry
system. The USGS and ShakeAlert partners aim to improve and optimize telemetry for the system. The USGS and ShakeAlert partners aim to improve and optimize telemetry for the
earthquake-sensing network to support robust and rapid data delivery from the seismic and earthquake-sensing network to support robust and rapid data delivery from the seismic and
geodetic stations to the data processing centers under all circumstances.geodetic stations to the data processing centers under all circumstances.
investigating other telemetry options, including whether new technologies such as the First investigating other telemetry options, including whether new technologies such as the First
Responder Network Authority (FirstNet) or a satellite-based data transfer system operated by Responder Network Authority (FirstNet) or a satellite-based data transfer system operated by
Network Name: Location
Partners
Funding Sources
Number of Stations Contributing to ShakeAlert
California, Berkeley; California, Berkeley;
California Geological California Geological
USGS and Cal OES
>832
University of Oregon, University of Washington, EarthScope Consortium and USGS
USGS, Department of Energy, State of Washington, and State of Oregon
>283
EarthScope Consortium
NSF, NASA, and USGS
>500
Central Washington University; EarthScope Consortium; Oregon Department of Transportation; Western Canada Deformation Array; USGS Cascades Volcano Observatory; and other public or private entities.
NSF, NASA, and USGS
>100
Central Washington Central Washington
University; Lawrence University; Lawrence
Berkeley National Berkeley National
Laboratory; and USGSLaboratory; and USGS
USGS
33
USGS
USGS
140
USGS
USGS
8
Source: USGS, USGS, ShakeAlert Plan, 2018. , 2018.
Modified by CRS. Notes: Cal OES = California GovernorCal OES = California Governor
Foundation; USGS = U.S. Geological Survey.Foundation; USGS = U.S. Geological Survey.
f. f.
Figure 9. ShakeAlert Message Generation and Alert Delivery
Source: USGS, December 12, 2024. Modified by CRS
Notes: GNSS = Global Navigation Satellite Systems; EPIC = Earthquake Point-source Integrated Code; FinDer = Finite Fault Detector. The EPIC and FinDer algorithms use seismic data gathered by the seismic network (Figure 7). G-FAST = Geodetic First Approximation of Size and Timing; PGD = Peak Ground Deformation. The G-FAST algorithm uses geodetic data gathered by the geodetic network (Figure 8). EQ = earthquake; GM = ground motion; MMI = Modified Mercalli Intensity Scale (i.e., shaking intensity); M = magnitude. See Appendix for more information about magnitude and the MMI shaking intensity levels. IPAWS = Integrated Public Alert and Warning System; WEA = wireless emergency alert.
communication providers: (1) location and magnitude; (2) location, magnitude, and a contour communication providers: (1) location and magnitude; (2) location, magnitude, and a contour
map of the area that may receive intense shaking; and (3) location, magnitude, and a gridded map map of the area that may receive intense shaking; and (3) location, magnitude, and a gridded map
of the area that may receive intense shaking. Providers may subscribe to the message type or of the area that may receive intense shaking. Providers may subscribe to the message type or
types they want to use.types they want to use.
67 Communication of Earthquake Early Warnings
Once communication providers receive the ShakeAlert-powered alert messages, the providers use Once communication providers receive the ShakeAlert-powered alert messages, the providers use
various communication pathways (e.g., cell phones, public address systems, or machine-to-various communication pathways (e.g., cell phones, public address systems, or machine-to-
machine communications) to deliver EEWs to individuals and institutions. Generally, distributing machine communications) to deliver EEWs to individuals and institutions. Generally, distributing
ShakeAlert messages over different communication pathways increases the chance that people ShakeAlert messages over different communication pathways increases the chance that people
may receive and act on the alerts.may receive and act on the alerts.
powered messages to non-FEMA communication providers for distribution as EEWs.powered messages to non-FEMA communication providers for distribution as EEWs.
prepare before intense shaking reaches their location, depending on their distance from the prepare before intense shaking reaches their location, depending on their distance from the
seconds of the earthquakeseconds of the earthquake
station density near the event.station density near the event.
to specific areas within seconds and aims for any delays in delivery to be less than five seconds.to specific areas within seconds and aims for any delays in delivery to be less than five seconds.
72 Geotargeting (i.e., sending EEWs to specific areas) is intended to help reach only those affected Geotargeting (i.e., sending EEWs to specific areas) is intended to help reach only those affected
by the event; increase confidence in EEWs; limit the strain on commercial communication by the event; increase confidence in EEWs; limit the strain on commercial communication
systems, which may become overwhelmed or limited in the event of an emergency;systems, which may become overwhelmed or limited in the event of an emergency;
alerting fatigue; and improve response.alerting fatigue; and improve response.
magnitude and shaking intensity levels for sending an EEW to allow various communication magnitude and shaking intensity levels for sending an EEW to allow various communication
pathways to limit the EEWs to potentially damaging earthquakes only pathways to limit the EEWs to potentially damaging earthquakes only
Figure 10. Alert Communication Pathways and Minimum Thresholds Source: USGS, "Earthquake Early Warning Overview,Earthquake Early Warning Overview,
science/earthquake-early-warning-overviewscience/earthquake-early-warning-overview
. Notes: ShakeAlert sets minimum magnitude and Modified ShakeAlert sets minimum magnitude and Modified
for sending alerts from communication providers as for sending alerts from communication providers as
shaking intensity threshold listed above in the right columns). If the earthquake is significant enough to meet shaking intensity threshold listed above in the right columns). If the earthquake is significant enough to meet
these minimum thresholds and thus may cause damage, alerts can be sent as EEWs via five main communication these minimum thresholds and thus may cause damage, alerts can be sent as EEWs via five main communication
pathways (listed in the left column). The wireless emergency alert pathways (listed in the left column). The wireless emergency alert
sends EEW using this technology. Seesends EEW using this technology. See Appendix for more information about magnitude and the MMI shaking for more information about magnitude and the MMI shaking
intensity levels.intensity levels.
one to alert systems and machines. The system sets minimum magnitude and shaking intensity one to alert systems and machines. The system sets minimum magnitude and shaking intensity
(i.e., MMI) levels for sending alerts as EEWs, and the magnitude and MMI minimum thresholds (i.e., MMI) levels for sending alerts as EEWs, and the magnitude and MMI minimum thresholds
differ for the five different communication pathways differ for the five different communication pathways (Figure
EEWs to individuals via four pathways:EEWs to individuals via four pathways:
pathway: established machine-to-machine communication systems. This automated pathway: established machine-to-machine communication systems. This automated
communication allows institutions, such as public transit systems, to take automated protective communication allows institutions, such as public transit systems, to take automated protective
actions actions (Figure
fastest machine-to-machine systems and cell phone apps via Wi-Fi or cellular networks fastest machine-to-machine systems and cell phone apps via Wi-Fi or cellular networks
within several tens of seconds, if at all.within several tens of seconds, if at all.
institutional communication pathways (e.g., public address announcements or institutional institutional communication pathways (e.g., public address announcements or institutional
systems, such as email and cell phones in buildings) also varies. The fastest alerts are via systems, such as email and cell phones in buildings) also varies. The fastest alerts are via
institutional services connected to Wi-Fi networks (e.g., cell phones or public address systems on institutional services connected to Wi-Fi networks (e.g., cell phones or public address systems on
Wi-Fi), which can deliver EEWs in a few seconds in some cases.Wi-Fi), which can deliver EEWs in a few seconds in some cases.
76 FEMA Communication Pathways
Threat Alerts) to individuals in targeted locations through Threat Alerts) to individuals in targeted locations through
provide secure, authenticated emergency and lifesaving information sent by an authorized alerting provide secure, authenticated emergency and lifesaving information sent by an authorized alerting
authority (e.g., state police, local sheriff, National Weather Service, or the USGS).authority (e.g., state police, local sheriff, National Weather Service, or the USGS).
alerting authorities, once approved by FEMA, purchase FEMA-approved software, which they alerting authorities, once approved by FEMA, purchase FEMA-approved software, which they
use to send alerts that comply with FEMA standards (e.g., FEMAuse to send alerts that comply with FEMA standards (e.g., FEMA
and Federal Communications Commission [FCC] rules). FEMA must authenticate alerts, such as and Federal Communications Commission [FCC] rules). FEMA must authenticate alerts, such as
EEWs, before they are distributed, which could lengthen the delivery time. FEMA distributes the EEWs, before they are distributed, which could lengthen the delivery time. FEMA distributes the
alerts through many communication pathways simultaneously to the area specified by the alerting alerts through many communication pathways simultaneously to the area specified by the alerting
Figure 11. FEMA Communication Pathways
Source: USGS, ShakeAlert Plan, 2018 (Figure 9). Modified by CRS.
Notes: Alerting authorities, such as ShakeAlert, submit an alert message to FEMA's Integrated Public Alert and Warning System (IPAWS) Open Platform for Emergency Networks (OPEN) gateway using a Common Alerting Protocol (CAP)-compliant message. IPAWS delivers alerts to alerting disseminators. People receive these alerts through the listed dissemination pathways and receive the alerts on the listed devices. FEMA, "Integrated Public Alert and Warning System," https://www.fema.gov/emergency-managers/practitioners/integrated-public-alert-warning-system. Canada's Multi-Agency Situational Awareness System (MASAS) is interoperable with IPAWS and other communication pathways (see Canada's "Welcome to the MASAS Exchange," https://www.canops.org/masas). Canada and the United States aim to cooperate on EEWs that impact both countries. Using WEA technology, cellular carriers send alerts over their cellular networks to cell phone Using WEA technology, cellular carriers send alerts over their cellular networks to cell phoneusers within the targeted area. Cellular carriers AT&T, T-Mobile, and Verizon voluntarily users within the targeted area. Cellular carriers AT&T, T-Mobile, and Verizon voluntarily
participate in FEMAparticipate in FEMA
subscribe to the service; carriers send EEWs to all cell phones operating in the affected area. A subscribe to the service; carriers send EEWs to all cell phones operating in the affected area. A
challenge with the technology is that it is built into the devicechallenge with the technology is that it is built into the device
cell phone app developers, which makes it difficult to upgrade or use with another app.cell phone app developers, which makes it difficult to upgrade or use with another app.
IPAWS communication pathways IPAWS communication pathways (Figure
approved EEW that states approved EEW that states
USGS ShakeAlert.USGS ShakeAlert.
networks to wireless devices, such as cell phones.networks to wireless devices, such as cell phones.
including extending alert messages from 90 characters to 360 characters, allowing uniform including extending alert messages from 90 characters to 360 characters, allowing uniform
resource locators (URLs) in messages, sending Spanish language messages, and geotargeting.resource locators (URLs) in messages, sending Spanish language messages, and geotargeting.
78 These new capabilities often require upgrades to all elements of the alerting system. In These new capabilities often require upgrades to all elements of the alerting system. In
FCC reported that most cell phones in use can receive WEA messages but some cannot (mainly FCC reported that most cell phones in use can receive WEA messages but some cannot (mainly
older phones).older phones).79 Some of these WEA-capable phones can receive the longer 360-character
geotargeted alerts.geotargeted alerts.
rate when FEMA issued a nationwide test alert.rate when FEMA issued a nationwide test alert.
alerts and EEWs when they upgrade to new, more advanced technologies. In addition, more alerts and EEWs when they upgrade to new, more advanced technologies. In addition, more
precise geotargeting may conserve communication bandwidth in an emergency, when precise geotargeting may conserve communication bandwidth in an emergency, when
USGS has License to Operate (LtO) partners that are licensed to use the ShakeAlert-powered USGS has License to Operate (LtO) partners that are licensed to use the ShakeAlert-powered
only for earthquakes that meet or exceed the minimum magnitude and shaking intensity only for earthquakes that meet or exceed the minimum magnitude and shaking intensity
thresholds set by ShakeAlert (thresholds set by ShakeAlert (
EEWs rapidly, preferably with delays of less than five seconds.EEWs rapidly, preferably with delays of less than five seconds.
messages to create and distribute EEWs via cell phones, internet, radio, television, public address messages to create and distribute EEWs via cell phones, internet, radio, television, public address
systems, machine-to-machine communication for critical operations, and other systems, machine-to-machine communication for critical operations, and other
50 locations.50 locations.
LtOs.LtOs.
2024 License to Operate
Partner ShakeAlert-Powered Alerts
Communication Services Sector(s) of Operation
Allen Institute
The scientific research institute sends EEWs to employee computers.
Research Institute
Early Warning Labs LLC
Proprietary hardware integration to send automatic alerts through existing infrastructure such as fire alarms, public address systems, and IP phone networks.
Education, Emergency Management, Health Care, Mass Notification, Municipal and Residential Buildings, and Transportation
Everbridge
Coast (not an EEW) sent to staff in Coast (not an EEW) sent to staff in
Public Safety Answering Point facilities in Public Safety Answering Point facilities in
California and Oregon.California and Oregon.
Public Safety and Response
Global Security Systems/ALERT FM
EEWs encoded in commercial FM radio to purpose-built devices.
Mass Notification
Alerts app in California, Oregon, and Alerts app in California, Oregon, and
Mass Notification
Jet Propulsion Laboratory (JPL)
EEWs delivered via automated alert to staff, automated opening of JPL fire department bay doors, and automated tools to place JPL Deep Space Network antennas into safe modes.
JPL
Kinemetrics
EEWs delivered via audio and visual alerts in buildings plus rapid assessments for building occupant safety.
Public Safety and Response in Buildings
MetroLink/Rail Pros – Los Angeles Metropolitan Area Transit
EEWs delivered with machine-to-machine automated systems via integration with positive train control systems.
Transportation
RH2 Engineering
EEWs delivered with machine-to-machine automated systems integrated with water and sewage system controls.
Utilities (water)
San Francisco Bay Area Rapid Transit District (BART)
EEWs delivered with machine-to-machine automated systems integrated with positive train control systems.
Transportation
SkyAlert
address systems and SkyAlert wireless address systems and SkyAlert wireless
devices for audio and visual EEWs.devices for audio and visual EEWs.
Emergency Management
University of California, Berkeley/MyShake
Oregon, and Washington.Oregon, and Washington.
Mass Notification
Valcom
with public address systems.with public address systems.
Education
Varius, Inc.
with water and sewage system controls.with water and sewage system controls.
Utilities (water), Education
effective nonfederal communication pathways to warn individuals of the approach of intense effective nonfederal communication pathways to warn individuals of the approach of intense
ground shaking with enough time to take protective action. Three LtO partner organizations and ground shaking with enough time to take protective action. Three LtO partner organizations and
one state agency have approved cell phone apps to send ShakeAlert-powered EEWs through four one state agency have approved cell phone apps to send ShakeAlert-powered EEWs through four
California, Oregon, and Washington (about 15.6 million devicesCalifornia, Oregon, and Washington (about 15.6 million devices
A review published in 2024 analyzed the status and performance of ShakeAlert from October 17, 2019, to September 1, 2023.94 According to the review, there were 53 earthquakes within the alerting boundary with a magnitude of 4.5 or greater (i.e., the alerting threshold).95 ShakeAlert sent out alerts for 41 of these 53 earthquakes; 7 earthquakes were mislocated, and 5 earthquakes had underestimated magnitudes (i.e., below the alert threshold), so no alerts were sent. Some of the missed earthquakes were located at the edges or outside of the observing network (i.e., offshore), where real-time observations were limited, leading to errors in locations and/or magnitude. The miss rate of 22.6% is above the performance standard of a 10% or less miss rate set for ShakeAlert. The review discusses how ShakeAlert is working to reduce the miss rate through improvements in the seismic data algorithms, adding the geodetic data algorithms to ShakeAlert operations, improving telemetry, and improving the seismic and geodetic observing network.96
According to the review, most users received the 41 alerts through cell phone applications. Accurate alerts were prepared within 5 seconds of the earthquake's origin time in the best-case scenarios and within 6-20 seconds in other scenarios.97 Some alerts distributed via FEMA's WEA had delivery times slower than the performance requirements of a few seconds. These results are generally consistent with a controlled environment test and community feedback, which showed that FEMA's WEA median delivery time frame was 6-12 seconds for EEW for smart phones and non-smart phones.98
The ShakeAlertmiles southeast of South Lake Tahoe, resulting in confusion and under-alerting of the shaking miles southeast of South Lake Tahoe, resulting in confusion and under-alerting of the shaking
intensity in the area impacted by the event (i.e., alerts were not sent to people who experienced intensity in the area impacted by the event (i.e., alerts were not sent to people who experienced
ground shaking within the threshold of the EEW system).ground shaking within the threshold of the EEW system).
inaccurate because the earthquake was near the edge of the network, where the seismic station inaccurate because the earthquake was near the edge of the network, where the seismic station
Communication Pathways Performance: Delivery of Earthquake
Early Warnings
ShakeAlert messages for the ShakeAlert messages for the
41 alerts between October 17, 2019, and September 1, 2023, were delivered as EEWs to individuals and institutions via multiple communication pathways were delivered as EEWs to individuals and institutions via multiple communication pathways
(Figure
ShakeAlert, and other pathways that use Wi-Fi or cellular networks (including many cell phone ShakeAlert, and other pathways that use Wi-Fi or cellular networks (including many cell phone
apps) generally delivered the alert messages within a few seconds. In general, these apps) generally delivered the alert messages within a few seconds. In general, these
communication pathways met the USGScommunication pathways met the USGS
institutions so they had enough time to take protective actions before the intense shaking arrived institutions so they had enough time to take protective actions before the intense shaking arrived
at their locations.at their locations.
phones, or machine-to-machine communication) has benefits and challenges.phones, or machine-to-machine communication) has benefits and challenges.
example, deliver EEW alerts faster than other communication pathways; these apps typically example, deliver EEW alerts faster than other communication pathways; these apps typically
deliver EEWs to cell phones within a few seconds of receiving a ShakeAlert message.deliver EEWs to cell phones within a few seconds of receiving a ShakeAlert message.
downside of these EEW apps is that three of the four require users to download the app to their downside of these EEW apps is that three of the four require users to download the app to their
cell phones (the Google app is built in and does not require owners of Android-based devices to cell phones (the Google app is built in and does not require owners of Android-based devices to
download an app). If users do not download the app, they cannot receive the EEW. Conversely, download an app). If users do not download the app, they cannot receive the EEW. Conversely,
WEA alerts sent from IPAWS to cell phones reach all operational cell phones in the targeted area; WEA alerts sent from IPAWS to cell phones reach all operational cell phones in the targeted area;
people do not need to opt in or download an app to receive the alert. Further, Wi-Fi or cellular people do not need to opt in or download an app to receive the alert. Further, Wi-Fi or cellular
networks must be operational for people to receive EEWs on their cell phones. If an earthquake networks must be operational for people to receive EEWs on their cell phones. If an earthquake
damages or destroys Wi-Fi or cellular networks, people may not be able to get EEWs on their cell damages or destroys Wi-Fi or cellular networks, people may not be able to get EEWs on their cell
phones. Experts generally assert that multiple communication pathways should be used in case phones. Experts generally assert that multiple communication pathways should be used in case
one pathway is damaged or destroyed.one pathway is damaged or destroyed.
phone apps are the fastest way to warn personnel using electronic devicesphone apps are the fastest way to warn personnel using electronic devices
systems at institutions that use emails, text messages, or reverse 911 for EEWs may not deliver systems at institutions that use emails, text messages, or reverse 911 for EEWs may not deliver
the warning in time for people to take protective action. Communication pathways such as public the warning in time for people to take protective action. Communication pathways such as public
address systems or sirens in buildings are generally fast enough (i.e., the EEW is delivered within address systems or sirens in buildings are generally fast enough (i.e., the EEW is delivered within
a few seconds) if the systems are connected to Wi-Fi or cellular networks. So far, testing and a few seconds) if the systems are connected to Wi-Fi or cellular networks. So far, testing and
development by the USGS, ShakeAlert partners, and some LtOs show that EEW communication development by the USGS, ShakeAlert partners, and some LtOs show that EEW communication
via television, radio, computer, or social media is too slow to be effective. Work is ongoing to via television, radio, computer, or social media is too slow to be effective. Work is ongoing to
speed up delivery via these other communication pathways.speed up delivery via these other communication pathways.
109 Public Reaction to Earthquake Early Warnings
EEWs may reduce risks only if the public receives the warnings, believes the warnings, and takes EEWs may reduce risks only if the public receives the warnings, believes the warnings, and takes
immediate protective actions. Past and ongoing surveys study how much of the public knows immediate protective actions. Past and ongoing surveys study how much of the public knows
about ShakeAlert and how much of the public favors having an EEW system. One 2016 poll in about ShakeAlert and how much of the public favors having an EEW system. One 2016 poll in
California found that 88% of the sampled population supported building a statewide EEW system California found that 88% of the sampled population supported building a statewide EEW system
in California and 75% were willing to pay an additional tax to fund it.in California and 75% were willing to pay an additional tax to fund it.
USGS and ShakeAlert partners seek to study how people react to EEWs and whether they find USGS and ShakeAlert partners seek to study how people react to EEWs and whether they find
the EEWs valuable. According to previous work in other countries and ongoing ShakeAlert the EEWs valuable. According to previous work in other countries and ongoing ShakeAlert
surveys, individuals do not always immediately DCHO. This may occur because individuals surveys, individuals do not always immediately DCHO. This may occur because individuals
pause, wait for confirmation of the event or for other people to react, try to help others first, and pause, wait for confirmation of the event or for other people to react, try to help others first, and
for other reasons.for other reasons.
's reaction are consistent with the public reaction to EEW systems in other countries, such as Japan reaction are consistent with the public reaction to EEW systems in other countries, such as Japan
and New Zealand.and New Zealand.
a warning from ShakeAlert were tolerant of potential flaws in the system, were optimistic about a warning from ShakeAlert were tolerant of potential flaws in the system, were optimistic about
reducing their risk if they received a timely EEW, and saw value in ShakeAlert.reducing their risk if they received a timely EEW, and saw value in ShakeAlert.
and current work suggest the public supports an EEW system and the public wants to receive an and current work suggest the public supports an EEW system and the public wants to receive an
EEW if they are in harmEEW if they are in harm
ShakeAlert Administration
Responsibility and Governance
The USGS leads the ShakeAlert cooperative project. State, academic, and nonprofit organization The USGS leads the ShakeAlert cooperative project. State, academic, and nonprofit organization
considers ShakeAlert activities to be part of ANSS, which is overseen by the USGS EHP.considers ShakeAlert activities to be part of ANSS, which is overseen by the USGS EHP.
USGS and ShakeAlert partners coordinate with FEMA and NSF on components of the system USGS and ShakeAlert partners coordinate with FEMA and NSF on components of the system
and to fulfill related NEHRP responsibilities.and to fulfill related NEHRP responsibilities.
coordinate with the National Oceanic and Atmospheric Administration (NOAA) and NASA, coordinate with the National Oceanic and Atmospheric Administration (NOAA) and NASA,
because these agencies support research and development that contributes to advancing EEW because these agencies support research and development that contributes to advancing EEW
in collaboration with the USGS and other ShakeAlert partners. The State of California authorized in collaboration with the USGS and other ShakeAlert partners. The State of California authorized
Cal OES in collaboration with the USGSCal OES in collaboration with the USGS
California, California, Berkeley; California Geological SurveyCalifornia Geological Survey
other stakeholders to develop a comprehensive statewide EEW system through a public-private other stakeholders to develop a comprehensive statewide EEW system through a public-private
partnership in 2013. The partnership was not authorized to receive appropriations from the partnership in 2013. The partnership was not authorized to receive appropriations from the
California General Fund but sought funding for the development of the statewide system from California General Fund but sought funding for the development of the statewide system from
other sources.other sources.
in the state treasury and allowed appropriations from the General Fund for seismic safety and in the state treasury and allowed appropriations from the General Fund for seismic safety and
earthquake-related programs, including the statewide EEW system. In addition, the 2016 earthquake-related programs, including the statewide EEW system. In addition, the 2016
legislation established the California Earthquake Early Warning Program within Cal OES and the legislation established the California Earthquake Early Warning Program within Cal OES and the
California Earthquake Early Warning Advisory Board to advise the director of Cal OES.California Earthquake Early Warning Advisory Board to advise the director of Cal OES.
public awareness and participation campaign of ShakeAlert in Oregon with the USGS, public awareness and participation campaign of ShakeAlert in Oregon with the USGS,
ShakeAlert partners, and ShakeAlert LtOs.ShakeAlert partners, and ShakeAlert LtOs.
Department, Emergency Management Division, coordinates a statewide public awareness and Department, Emergency Management Division, coordinates a statewide public awareness and
participation campaign of ShakeAlert with the USGS, ShakeAlert partners, and ShakeAlert participation campaign of ShakeAlert with the USGS, ShakeAlert partners, and ShakeAlert
LtOs.LtOs.
ShakeAlert ShakeAlert
Center for Scientific Research and Higher Education in Baja California Center for Scientific Research and Higher Education in Baja California
128 Funding Trends and Estimated Future Costs for ShakeAlert
Congress appropriated funds totaling $Congress appropriated funds totaling $
EEW capabilitiesEEW capabilities (Table 5). In addition, the USGS has cooperative agreements and distributes some of its . In addition, the USGS has cooperative agreements and distributes some of its
appropriated funds to ShakeAlert partners (appropriated funds to ShakeAlert partners (see Table 2) for research and development, operations for research and development, operations
and maintenance, and education and outreach components of ShakeAlert. Nonfederal sources of and maintenance, and education and outreach components of ShakeAlert. Nonfederal sources of
funding, mostly from California state and local agencies, contributed another $funding, mostly from California state and local agencies, contributed another $
ShakeAlert between 2012 and ShakeAlert between 2012 and
2024 (Table 6). USGS ShakeAlert Funding
Table 5 shows enacted appropriations for EEW within the USGS EHP from FY2006 to shows enacted appropriations for EEW within the USGS EHP from FY2006 to
development, testing, and demonstration from FY2006 to FY2014. In addition, Congress development, testing, and demonstration from FY2006 to FY2014. In addition, Congress
provided the USGS with appropriations for operations, maintenance, construction, and repair of provided the USGS with appropriations for operations, maintenance, construction, and repair of
critical USGS facilities in the American Recovery and Reinvestment Act (ARRA; P.L. 111-5), critical USGS facilities in the American Recovery and Reinvestment Act (ARRA; P.L. 111-5),
and EHP spent $4.4 million of ARRA funds to build EEW-related systems from 2009 to 2011. In and EHP spent $4.4 million of ARRA funds to build EEW-related systems from 2009 to 2011. In
FY2015, Congress appropriated $5 million for capital costs to begin to transition the EEW FY2015, Congress appropriated $5 million for capital costs to begin to transition the EEW
demonstration prototype into an EEW operational capability. demonstration prototype into an EEW operational capability.
Fiscal Year(s)
Base Funding
Capital Funding
7.5
2015
1.5
5.0
2016
8.2
—
2017
10.2
—
2018
12.9
10.0
2019
16.1
5.0
2020
19.0
6.7
2021
25.7
—
2022
—
2023
28.6
—
2024
28.6
—
Total
130.7
31.1
ShakeAlert through regular appropriations, except where noted. ShakeAlert through regular appropriations, except where noted. Base funding covers research and development covers research and development
and operations and maintenance for EEW activities and ShakeAlert. and operations and maintenance for EEW activities and ShakeAlert. Capital funding covers the costs of new covers the costs of new
equipment and new infrastructure and the costs for installing new stations or upgrading existing stations.equipment and new infrastructure and the costs for installing new stations or upgrading existing stations.
$4.4 $4.4
capabilities between 2009 and 2011.capabilities between 2009 and 2011.
than the USGS spent on earthquake-related activities that directly or indirectly support EEW. than the USGS spent on earthquake-related activities that directly or indirectly support EEW.
NSF, through research grants and cooperative agreements, supports research facilitating the NSF, through research grants and cooperative agreements, supports research facilitating the
development of EEW capabilities and ShakeAlert components; however, these grants and development of EEW capabilities and ShakeAlert components; however, these grants and
agreements also serve other purposes, and it is difficult to estimate what fraction of these funds agreements also serve other purposes, and it is difficult to estimate what fraction of these funds
supported research that advanced EEW capabilities and ShakeAlert.supported research that advanced EEW capabilities and ShakeAlert.
FCC are working with the USGS and ShakeAlert partners to improve communication pathways FCC are working with the USGS and ShakeAlert partners to improve communication pathways
for EEWs.for EEWs.
government) totaling $government) totaling $
supported the development of ShakeAlert system components, education and outreach, and other supported the development of ShakeAlert system components, education and outreach, and other
activities. The largest contributor is Cal OES, which has provided $activities. The largest contributor is Cal OES, which has provided $
Cal OES funds (1) the installation and upgrading of seismic and geodetic stations in California, Cal OES funds (1) the installation and upgrading of seismic and geodetic stations in California,
(2) improvements in and integration of telemetry for ShakeAlert raw data in the state, (3) a (2) improvements in and integration of telemetry for ShakeAlert raw data in the state, (3) a
comprehensive public awareness and participation campaign, (4) research and development of comprehensive public awareness and participation campaign, (4) research and development of
various communication pathways (e.g., radio and television) for rapid EEW, and (5) various communication pathways (e.g., radio and television) for rapid EEW, and (5)
administration and management of the Earthquake Early Warning Program in California. administration and management of the Earthquake Early Warning Program in California. In 2018, Cal Cal
year.year.
provided $5.6 million, mostly for new seismic stations, from funds granted to the initiative by provided $5.6 million, mostly for new seismic stations, from funds granted to the initiative by
FEMA.FEMA.
appropriated funds for 15 new seismic stations, the Oregon Department of Geology and Mineral appropriated funds for 15 new seismic stations, the Oregon Department of Geology and Mineral
Industries funded 27 new stations, and the Eugene Water and Electric Board purchased equipment Industries funded 27 new stations, and the Eugene Water and Electric Board purchased equipment
for two stations.134 Table 6. Nonfederal Funding for the ShakeAlert System
Time Frame
Source
Amount
2012-2015
Foundation
6.5
5.6
2016-2018
3.6
2016-2024
Cal OES
110.1
2015-2020
Oregon
8.5
2019
Washington
1.2
2012-2024
All Nonfederal Sources
135.5
Earthquake Early Warning Business Plan Update, ,
wp-content/uploads/Earthquake-Tsunami-Volcano/Documents/California-EEW-Program-Annual-Business-Plan-2023-2024-Update.pdf. Notes: Cal OES = California GovernorCal OES = California Governor
Urban Area Security Initiative, which provided funds from the Federal Emergency Management Agency.Urban Area Security Initiative, which provided funds from the Federal Emergency Management Agency.
Comparing ShakeAlert with other EEW systems may help stakeholders improve the ShakeAlert system, consider alternative components or technology, and coordinate and cooperate on advancing EEW throughout the world (Figure 12). Two types of EEW systems are used today, a standard EEW system with an earthquake sensing network and a non-standard EEW system with a cell phone-based network.
Seismic- and Geodetic-Based Network A standard EEW system consists of an earthquake-sensing network that includes seismic and/or geodetic stations spatially distributed around active faults for optimal earthquake detection. ShakeAlert is a standard EEW system as described in detail in this report. These networks can generally rapidly and accurately detect P-waves and provide effective EEWs (Figure 5). The USGS and ShakeAlert partners may consider how EEW systems in other countries are working and how countries might share earthquake understanding, risk reduction, and any techniques to better detect and mitigate earthquake hazards. Canada, China, India, Italy, Japan, Mexico, Romania, South Korea, Taiwan, and Turkey have regional to nationwide public-alerting EEW systems that use standard earthquake-sensing networks. Austria, Chile, Costa Rica, El Salvador, Greece, Iceland, Italy, Israel, New Zealand, Nicaragua, Slovenia, Spain, and Switzerland are testing similar EEW systems.135 The Canadian Earthquake Early Warning System began sending alerts in British Columbia in May, 2024, using ShakeAlert Message Generation software (Figure 9) and by sharing data.136Figure 12. Timeline of Public EEW by Country or Region and Population Size Alerted Source: Sara K. McBride et al., "Evidence-Based Guidelines for Protective Actions and Earthquake Early Warning Systems," Geophysics, vol. 87, no. 1 (January-February 2022), WA77-WA102, https://doi.org/10.1190/GEO2021-0222.1.
Notes: Limited alerts have been sent in Costa Rica and El Salvador but are not shown on this graphic. The limited alerts sent in 2021 are from Google's Android Earthquake Alerts app.
A comparison of ShakeAlert with standard earthquake-sensing networks used in other countries may help reveal the optimal location, deployment, station technology, telemetry technology, and data analysis techniques for earthquake detection and the most effective communication pathways for EEWs. Each network was developed based on knowledge of faults, past earthquakes, geology, and earthquake risks. Mexico City established the first public EEW system in 1991.137 Today, Mexico's earthquake-sensing network uses fewer than 100 seismic stations to detect earthquakes in an area comparable to the area of California, Oregon, and Washington combined. Mexico's system uses different seismic algorithms than other EEW systems. Mexico's system provides EEWs to Mexico City and a few other cities primarily via tens of thousands of radios and thousands of sirens installed throughout urban areas.
Japan's EEW system, established in 2006, uses more than 850 seismic stations on land and on the seafloor, covering an area comparable to the area of California.138 Japan invested in an offshore earthquake-sensing network after the 2011 Tohoku earthquake to cover major fault systems offshore.139 Japan's system uses different seismic algorithms than other EEW systems. Japan provides EEWs nationwide through multiple communication pathways including television, radio, and cell phones.
Fixed or Crowd-Sourced Cell Phone Network A fixed or crowd-sourced cell phone network may detect accelerations caused by earthquakes, and these detections may be used to provide some warning about earthquakes.140 Cell phones have miniature accelerometers and Global Navigation Satellite System (GNSS) receivers that are not as accurate or sensitive as seismic or geodetic instruments, respectively, but cell phones can function as approximate earthquake detectors. In many cases, a cell phone-based network may not be able to detect the first arriving P-waves but may detect the stronger and later-arriving S-waves (Figure 5); this means the EEW may be delayed and the cell phones used to detect the S-waves provide no warning to their owners in advance of intense ground shaking. In addition, cell phones provide a communication pathway and may send EEWs to other cell phones using earthquake detection apps via Wi-Fi or cellular networks with lower latency than transferring the alert from an EEW system to alert providers (Figure 9).A fixed network may consist of cell phones installed in buildings or other convenient locations where there is a power supply and protection from the environment. Because the cell phones are fixed, there is less data analysis and less confusion about the detected signals, so in theory it should be easier to distinguish an earthquake from other signals, such as a truck passing by a building. The USGS—with support from the U.S. Agency for International Development and in cooperation with researchers from the United States, Costa Rica, and Chile—tested a temporary fixed cell phone network in part of Costa Rica.141 The demonstration showed that an operational EEW system could be established at a lower cost than a standard EEW system; however, the system may not provide as much warning with as much accuracy and speed as a standard EEW system.
Google has developed an EEW app called Android Earthquake Alerts by crowd-sourcing data from Android-based phones.142 The app collects signals from Android-based phones and determines if the signals are from an earthquake and where the earthquake is located.143 If an earthquake is detected, the Android Earthquake Alerts app sends alerts via Android-based phones. In California, Oregon, and Washington, the Android Earthquake Alerts app uses ShakeAlert-powered alerts and does not use cell phone crowd-sourcing. The Android Earthquake Alerts app uses crowd-sourcing cell phone data in countries or regions that do not have an EEW system (Figure 12).144 The Android Earthquake Alerts app has had mixed results, such as EEW failures for the 2023 Turkey earthquakes and false alarms (alerts but no earthquake) in Brazil in 2025.145 Two factors that likely contributed to some of these Android Earthquake Alerts problems and are concerns for any EEW system are (1) it is not possible to provide EEW to people or facilities close to an earthquake because the intense shaking arrives within seconds and (2) offshore earthquakes or other offshore activity is typically outside the EEW observing system, and any signals picked up in the onshore system may lead to inaccurate earthquake characteristics (i.e., magnitude and location) or false alarms. Future of ShakeAlert and EEW Science and TechnologyShakeAlert and other EEW systems are dynamic systems that may continue to evolve based on innovative research and technology. Innovative research and technology in seismology and geodesy may include machine learning/artificial intelligence, cloud computing and supercomputing, instrument innovations, and distributed acoustic sensing (i.e., a fiber-optic cable as a distributed earthquake detector).146 The USGS EHP supports USGS research and external grants to advance earthquake science, earthquake engineering, EEW, and other earthquake products.147 Other federal agencies—especially NSF, NIST, and FEMA, as coordinating agencies in NEHRP—support cutting-edge and innovative research and technology in seismology and geodesy to advance earthquake science and earthquake engineering.148
Issues for CongressShakeAlert has been operating in California since October 2019 and in Oregon and Washington since 2021. Given that the EEW system has been operational for multiple years, additional information to assess ShakeAlert's performance and effectiveness may be useful to Congress as it considers authorization and appropriations options for related federal programs, particularly NEHRP. The USGS analysis of the performance of ShakeAlert from October 17, 2019, to September 1, 2023, shows that some earthquakes were missed or miscalculated because of inadequate station coverage.149 The USGS indicates that more seismic stations plus the continued integration of the geodetic data into the data processing may improve the performance of ShakeAlert on the West Coast. Further, the USGS and ShakeAlert partners aim to improve the data algorithms and data processing to prepare more timely and accurate alert messages. Congress may consider the USGS and ShakeAlert partners' aim to increase the size of the earthquake-sensing network on the West Coast and to improve ShakeAlert, as discussed in the 2018 USGS ShakeAlert Plan and the USGS analysis of ShakeAlert's performance.150
In addition, the Government Accountability Office (GAO) has completed two assessments, one on the EEW system in 2021 and one on NEHRP in 2022.151 Congress may consider the GAO recommendations and the federal agency responses and actions to these recommendations. In response to many of GAO's recommendations in 2021, the USGS completed a USGS Earthquake Hazards Program Decadal Science Strategy, 2024-2033.152 The USGS partially addressed a GAO recommendation to establish a schedule and milestones for ShakeAlert implementation consistent with best practices in GAO's schedule guide due to costs.153 In 2022, GAO recommended that NIST as part of NEHRP and in coordination with state and local entities complete a national risk assessment of earthquake resilience in communities; as of February 2025, NIST was developing a plan for an assessment.154 Congress also may consider the NEHRP 2022-2029 Strategic Plan, completed after the GAO reports, and what the plan says about ShakeAlert.155
Congress may consider the importance, uses, and status of seismic and geodetic networks in the United States, U.S. territories, North and South America, Antarctica, and globally.156 Seismic and geodetic networks that are now components Seismic and geodetic networks that are now componentsof ShakeAlertof ShakeAlert
used for ShakeAlert while continuing to serve these other purposes. An evaluation of whether used for ShakeAlert while continuing to serve these other purposes. An evaluation of whether
these components are effective for EEW and how these components might be used effectively for these components are effective for EEW and how these components might be used effectively for
multiple purposes, perhaps with further coordination among the component operators, also may multiple purposes, perhaps with further coordination among the component operators, also may
parts of some states). For example, the 2018 USGS ShakeAlert Plan parts of some states). For example, the 2018 USGS ShakeAlert Plan
an implementation plan for ShakeAlert in Alaska in FY2022 appropriationsan implementation plan for ShakeAlert in Alaska in FY2022 appropriations
Congress may consider requesting FEMA to evaluate its communication pathways and make Congress may consider requesting FEMA to evaluate its communication pathways and make
suggestions about how FEMA may improve its technology and techniques to meet the challenge suggestions about how FEMA may improve its technology and techniques to meet the challenge
of rapid, targeted mass notification for earthquakes.of rapid, targeted mass notification for earthquakes.
whether these improvements may be applied for rapid warning about other hazards, such as whether these improvements may be applied for rapid warning about other hazards, such as
further developing communication protocols for rapid and targeted mass notification for further developing communication protocols for rapid and targeted mass notification for
tornadoes.tornadoes.
pathways operate in coordination or in parallel with nonfederal communication pathways to pathways operate in coordination or in parallel with nonfederal communication pathways to
provide the most effective disaster warnings to states and civilian populations in endangered provide the most effective disaster warnings to states and civilian populations in endangered
areas. In particular, the continued growth of cell phone EEW apps for public warnings may create areas. In particular, the continued growth of cell phone EEW apps for public warnings may create
issues regarding security, privacy, accuracy, reliability, accessibility, and authority. Congress may issues regarding security, privacy, accuracy, reliability, accessibility, and authority. Congress may
consider how agreements between federal agencies, such as the USGSconsider how agreements between federal agencies, such as the USGS
communication providers address these issues. These oversight and policy considerations may communication providers address these issues. These oversight and policy considerations may
system or to support annual operations and maintenance in the future.system or to support annual operations and maintenance in the future.
continue to provide funding for ShakeAlert, there are a range of options to consider, such as continue to provide funding for ShakeAlert, there are a range of options to consider, such as
annual appropriations or through shared costs similar to those that support other observing annual appropriations or through shared costs similar to those that support other observing
networks in the United States that are a mix of federal- and state-funded initiatives (e.g., NOAA networks in the United States that are a mix of federal- and state-funded initiatives (e.g., NOAA
Continuously Operating Reference Stations and USGS Streamgaging Network).Continuously Operating Reference Stations and USGS Streamgaging Network).
options for consideration may include funding aspects of ShakeAlert through established NSFoptions for consideration may include funding aspects of ShakeAlert through established NSF, NIST, or or
FEMA federal grants, contracts, or cooperative agreementsFEMA federal grants, contracts, or cooperative agreements, such as those listed by NEHRP,165 or through new NSF or through new NSF, NIST, or FEMA federal or FEMA federal
grants, contracts, or cooperative agreements. In addition, Congress may consider policy options grants, contracts, or cooperative agreements. In addition, Congress may consider policy options
that would enable NOAA or NASA to contribute funds for ShakeAlert as well as research and that would enable NOAA or NASA to contribute funds for ShakeAlert as well as research and
development for EEW capabilities.development for EEW capabilities.
to support ShakeAlert and to support ShakeAlert and
receive appropriations for earthquake hazards risk reduction through NEHRP or for research and receive appropriations for earthquake hazards risk reduction through NEHRP or for research and
development related to hazard mitigation objectivesdevelopment related to hazard mitigation objectives
USGS for EEW, USGS for EEW,
because those funds were not specifically appropriated for ShakeAlert.because those funds were not specifically appropriated for ShakeAlert.
Appendix. Earthquake Magnitude, Shaking
Intensity Scale, and Hazards
Earthquake magnitude is determined for every observed earthquake and often estimated for older Earthquake magnitude is determined for every observed earthquake and often estimated for older
events that happened before earthquake-sensing instruments existed in order to compare these events that happened before earthquake-sensing instruments existed in order to compare these
events to current events and to estimate the possible recurrence rate of earthquakes on a fault.events to current events and to estimate the possible recurrence rate of earthquakes on a fault.
166 Magnitude is rapidly estimated for earthquake early warning (EEW), and the estimated Magnitude is rapidly estimated for earthquake early warning (EEW), and the estimated
magnitude may change as more data are collected or because the earthquake may continue to magnitude may change as more data are collected or because the earthquake may continue to
to a larger area of movement and a larger magnitude event). A changing magnitude estimate can to a larger area of movement and a larger magnitude event). A changing magnitude estimate can
complicate EEW and can make EEW less effective in reducing risks because the warning must be complicate EEW and can make EEW less effective in reducing risks because the warning must be
rapid, leaving little to no time to reassess an estimated magnitude.rapid, leaving little to no time to reassess an estimated magnitude.
using a familiar parameter and to compare the event to previous newsworthy events. For using a familiar parameter and to compare the event to previous newsworthy events. For
earthquake scientists, magnitude provides a measurement of the length and area of the fault that earthquake scientists, magnitude provides a measurement of the length and area of the fault that
slipped and the strength of the rock involved in the rupture. These parameters improve an slipped and the strength of the rock involved in the rupture. These parameters improve an
understanding of what causes an earthquake and whether the fault is more or less likely to have understanding of what causes an earthquake and whether the fault is more or less likely to have
an earthquake over a specified future period. Magnitude can be calculated in different ways, and an earthquake over a specified future period. Magnitude can be calculated in different ways, and
this report cites moment magnitude (M). Moment magnitude is based on the strength of the rock, this report cites moment magnitude (M). Moment magnitude is based on the strength of the rock,
the fault surface area that ruptures, and the amount of slip along the fault. This magnitude the fault surface area that ruptures, and the amount of slip along the fault. This magnitude
calculation may be the closest to the publiccalculation may be the closest to the public
represents the represents the
a larger magnitude event because there is more length and area that can slip, producing a larger a larger magnitude event because there is more length and area that can slip, producing a larger
moment magnitude event.moment magnitude event.
increases by about 32 times for each single step in magnitudeincreases by about 32 times for each single step in magnitude
much more energetic than an M8.0 event. An M9.0 event may cause surface shaking that is much much more energetic than an M8.0 event. An M9.0 event may cause surface shaking that is much
more intense, covers a larger area, and is of a longer duration than surface shaking from an M8.0 more intense, covers a larger area, and is of a longer duration than surface shaking from an M8.0
event. The public may not fully understand that each magnitude step means a much more event. The public may not fully understand that each magnitude step means a much more
energetic earthquake that may cause much more intense ground shaking. However, for EEW and energetic earthquake that may cause much more intense ground shaking. However, for EEW and
other earthquake notifications for the public, it is important to quickly estimate the magnitude and other earthquake notifications for the public, it is important to quickly estimate the magnitude and
determine where and how much intense shaking the earthquake may cause. In the case of the determine where and how much intense shaking the earthquake may cause. In the case of the
2011 M9.1 Tohoku earthquake, Japan2011 M9.1 Tohoku earthquake, Japan
leading to no warning or less warning (i.e., less intense shaking over a smaller area was expected leading to no warning or less warning (i.e., less intense shaking over a smaller area was expected
and the larger area that was impacted by the tsunami were not anticipated) for a much more and the larger area that was impacted by the tsunami were not anticipated) for a much more
Figure A-1. Earthquake Magnitude and Energy Released Source: The figure is from ShakeAlert, The figure is from ShakeAlert,
messaging_toolkit/graphics-library/messaging_toolkit/graphics-library/
. Note: For more details about magnitude and the amount of energy released for a given magnitude, see USGS For more details about magnitude and the amount of energy released for a given magnitude, see USGS
hazards/earthquake-magnitude-energy-release-and-shaking-intensityhazards/earthquake-magnitude-energy-release-and-shaking-intensity
used for EEW and in post-earthquake assessments to compare and describe earthquake intensity used for EEW and in post-earthquake assessments to compare and describe earthquake intensity
on the surface with one consistent, comparable parameter.on the surface with one consistent, comparable parameter.
of the shaking based on how intensely people feel the shaking and the amount of damage the of the shaking based on how intensely people feel the shaking and the amount of damage the
shaking causes to structuresshaking causes to structures (Table A-1). The scale is empirical and is based on previous . The scale is empirical and is based on previous
observations. For example, light shaking of MMI intensity IV refers to people indoors feeling the observations. For example, light shaking of MMI intensity IV refers to people indoors feeling the
shaking. For intensities greater than V, the expected experiences refer to the potential impact of shaking. For intensities greater than V, the expected experiences refer to the potential impact of
the shaking on structures. For example, violent shaking of MMI IX refers to structures that have the shaking on structures. For example, violent shaking of MMI IX refers to structures that have
Intensity
Shaking
Description
Not felt
Weak
Weak
Many people do not recognize it as an earthquake. Standing motor cars may rock Many people do not recognize it as an earthquake. Standing motor cars may rock
Light
Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy
Moderate
objects overturned. Pendulum clocks may stop.objects overturned. Pendulum clocks may stop.
Strong
fallen plaster. Damage slight.fallen plaster. Damage slight.
Very strong
Severe
overturned.
Violent
structures thrown out of plumb. Damage great in substantial buildings, with partial structures thrown out of plumb. Damage great in substantial buildings, with partial
Extreme
destroyed with foundations. Rails bent.destroyed with foundations. Rails bent.
Source: Douglas D. Given et al., Douglas D. Given et al., Revised Implementation Plan for the ShakeAlert System: An Earthquake Early
Warning System for the West Coast of the United States, USGS, Open-File Report 2018–1155, 2018. Modified by , USGS, Open-File Report 2018–1155, 2018. Modified by
CRS.CRS.
liquefaction liquefaction (Figure A-2).
determine whether any of these hazards may occur at or near the surface, whether the event may determine whether any of these hazards may occur at or near the surface, whether the event may
cause damage, and where the event may cause damage. Higher-magnitude earthquakes that cause damage, and where the event may cause damage. Higher-magnitude earthquakes that
release more energy and earthquakes at shallow depth may cause damaging surface hazards.release more energy and earthquakes at shallow depth may cause damaging surface hazards.
earthquake can trigger other natural hazards, such as tsunamis, landslides, fires, floods, or earthquake can trigger other natural hazards, such as tsunamis, landslides, fires, floods, or
volcanic eruptions. Earthquake hazards can damage property, such as structural cracks, structural volcanic eruptions. Earthquake hazards can damage property, such as structural cracks, structural
collapse, fires, explosions, floods, loss of power, loss of water supplies, loss of communication, collapse, fires, explosions, floods, loss of power, loss of water supplies, loss of communication,
and other damage. Earthquake hazards can cause injuries and fatalities. People are injured or and other damage. Earthquake hazards can cause injuries and fatalities. People are injured or
killed mostly by tripping and falling during ground shaking or by being hit or trapped under fallen killed mostly by tripping and falling during ground shaking or by being hit or trapped under fallen
objects or shake-damaged structures.objects or shake-damaged structures.
tsunami waves, fires, and floods, may injure or kill more people and damage more structures after tsunami waves, fires, and floods, may injure or kill more people and damage more structures after
Figure A-2. Earthquake Hazards
Source: U.S. Government Accountability Office (GAO), EARTHQUAKES Progress Made to Implement Early Warning System, But Actions Needed to Improve Program Management, GAO-21-129, March 2019 (modified by CRS).
Footnotes
Angela I. Lux et al., "Status and Performance of the ShakeAlert Earthquake Early Warning System: 2019-2023," Bull. Seismol. Soc. Am., 2024, doi: 10.1785/0120230259 (hereinafter Lux, 2024).
For more details, see the U.S. Geological Survey (USGS), "What Are the Effects of Earthquakes?," https://www.usgs.gov/natural-hazards/earthquake-hazards/science/what-are-effects-earthquakes?qt-science_center_objects=0#qt-science_center_objects.
Richard M. Allen et al., "The Status of Earthquake Early Warning Around the World: An Introductory Overview," Seismological Research Letters, vol. 80, no. 5 (September/October 2009), https://doi.org/10.1785/gssrl.80.5.682.
Jessica A. Strauss and Richard M. Allen, "Benefits and Costs of Earthquake Early Warning," Seismological Research Letters, vol. 87, no. 3 (May/June 2016), pp. 765-772, https://doi.org/10.1785/0220150149 (hereinafter Strauss, "Benefits," 2016).
USGS, "Earthquake Early Warning – Overview," https://www.usgs.gov/programs/earthquake-hazards/science/earthquake-early-warning-overview.
Telemetry is the automated recording and transmission of data from stations to processing centers.
Geodesy is the science of accurately measuring and understanding the Earth's geometric shape, orientation in space, and gravity field, and geodetic is anything related to geodesy. See also National Research Council, Precise Geodetic Infrastructure: National Requirements for a Shared Resource (Washington, DC: National Academies Press, 2010), https://doi.org/10.17226/12954 (hereinafter NRC, Precise Geodetic Infrastructure, 2010). Geodetic instruments provide positions that are accurate to a few millimeters to centimeters in optimal conditions, and this accuracy is important for earthquake measurements. The Global Navigation Satellite Systems (GNSS) receivers are similar to "GPS receivers" found in mobile devices in the basic way that they work. The receivers gather satellite signals from a GNSS satellite, which includes the U.S.-operated Global Positioning System (GPS) constellation of satellites, and determine their position in space and time. GPS receivers in mobile devices are miniaturized and not fixed (or stably mounted in one position) and are therefore less accurate in defining their position than geodetic instruments in earthquake-sensing networks.
Jeffrey J. McGuire et al., Expected Warning Times from the ShakeAlert® Earthquake Early Warning System for Earthquakes in the Pacific Northwest, USGS, USGS Open File Report No 2021-1026, 2021 (hereinafter USGS, Expected Warning Times, 2021).
Richard M. Allen and Diego Melgar, "Earthquake Early Warning: Advances, Scientific Challenges, and Societal Needs," Annual Review of Earth and Planetary Sciences, vol. 47 (2019), pp. 361-388, https://doi.org/10.1146/annurev-earth-053018-060457 (hereinafter Allen and Melgar, "EEW Advances," 2019).
CRS Report R43141, The National Earthquake Hazards Reduction Program (NEHRP): Overview and Issues for Congress, by Linda R. Rowan.
CRS Report R43141, The National Earthquake Hazards Reduction Program (NEHRP): Overview and Issues for Congress, by Linda R. Rowan.
See Federal Emergency Management Agency (FEMA), "Risk Management," https://www.fema.gov/emergency-managers/risk-management.
See USGS, "National Earthquake Information Center (NEIC)," https://www.usgs.gov/programs/earthquake-hazards/national-earthquake-information-center-neic.
USGS, "Products," https://www.usgs.gov/programs/earthquake-hazards/products.
Subduction zones are where tectonic plates converge, such that one plate is forced to bend and dive underneath another plate in a process called subduction by geoscientists (see USGS, "Introduction to Subduction Zones: Amazing Events in Subduction Zones," https://www.usgs.gov/special-topics/subduction-zone-science/science/introduction-subduction-zones-amazing-events. Strike-slip zones are where tectonic plates laterally slide past each other and create a zone of faults where the two plates converge (see Britannica, "Strike-Slip Fault," https://www.britannica.com/science/strike-slip-fault).
The Pacific Plate subducts beneath the North America Plate along the Alaska-Aleutian Arc Subduction Zone offshore of southern Alaska and the Aleutian Islands. The Alaska-Aleutian Arc Subduction Zone has generated multiple M8.0+ earthquake and tsunami sequences and these sequences may recur in the future. Six great earthquakes have occurred along the Alaska-Aleutian Arc Subduction Zone since 1900: 1906 M8.4 Rat Islands, 1938 M8.6 Shumagin Islands, 1946 M8.6 Unimak Island, 1957 M8.6 Andreanof Islands, 1964 M9.2 Prince William Sound, and 1965 M8.7 Rat Islands, Harley M. Benz et al., Seismicity of the Earth 1900-2010 Aleutian Arc and Vicinity, USGS, Open-File Report 2010-1083-B, https://pubs.er.usgs.gov/publication/ofr20101083B. The small population and sparse built environment limit the damage from these events and account for the lower earthquake risk in Alaska compared with some other states. Large Alaskan earthquakes may cause greater damage further away because of the tsunamis they trigger. Hawaii in particular has suffered significant losses from tsunamis triggered by Alaskan earthquakes. The 1946 M8.6 Aleutian Islands earthquake generated a tsunami, and the tsunami caused 5 fatalities in Alaska and 129 fatalities plus $26 million in 1946 dollars in damage in Hawaii.
The Juan de Fuca Plate subducts beneath the North America Plate along the Cascadia Subduction Zone (CSZ) offshore of Northern California, the Pacific Northwest, and parts of British Columbia, Canada. M8.0+ earthquakes, many with tsunamis occur on the CSZ every 570-590 years, on average. There is evidence of at least 12 M8.0+ earthquakes on the CSZ over the past 6,700 years. Robert C. Witter, Harvey M. Kelsey, and Eileen Hemphill-Haley, "Great Cascadia Earthquakes and Tsunamis of the Past 6700 Years, Coquille River Estuary, Southern Coastal Oregon," Geological Society of America Bulletin, vol. 115, no. 10 (October 1, 2003), pp. 1289-1306. The last large magnitude earthquake (between M8.7 and M9.2) that triggered a large tsunami was in January 1700, more than 500 years ago, Brian F. Atwater, The Orphan Tsunami of 1700 (Reston, VA: University of Washington Press/USGS, 2005). Earthquake probability forecasts estimate a 14% chance of a M8.0+ earthquake on the CSZ over the next 50 years, Alan Boyle, "Earthquake Experts Lay Out Latest Outlook for the 'Really Big One' That'll Hit Seattle," GeekWire, February 15, 2020.
For more details about earthquake hazards and risks to Puerto Rico and the U.S. Virgin Islands, see National Oceanic and Atmospheric Administration (NOAA) Ocean Explorer, "The Puerto Rico Trench: Implications for Plate Tectonics and Earthquakes and Tsunamis," https://oceanexplorer.noaa.gov/explorations/03trench/trench/trench.html.
See the USGS "Faults," https://www.usgs.gov/programs/earthquake-hazards/faults. See the USGS "Slab2 - A Comprehensive Subduction Zone Geometry Model," https://www.sciencebase.gov/catalog/item/.5aa1b00ee4b0b1c392e86467 and Gavin P. Hayes et al., "Slab2, a comprehensive subduction zone geometry model," Science, vol. 362, no. 6410 (October 5, 2018), pp. 58-61, https://doi.org/10.1126/science.aat4723.
See the USGS "Seismic Hazard Maps and Specific Data," https://www.usgs.gov/natural-hazards/earthquake-hazards/seismic-hazard-maps-and-site-specific-data. The USGS published a 2023 50-state update of the U.S. National Seismic Hazard Model on January 2, 2024, along with technical documents, data, and software describing the model. USGS, "2023 50-State Long-Term National Seismic Hazard Model," https://www.usgs.gov/programs/earthquake-hazards/science/2023-50-state-long-term-national-seismic-hazard-model-0.
For more information about Hazus models and FEMA's Hazus Program, see FEMA, "Hazus," https://www.fema.gov/flood-maps/products-tools/hazus.
These estimates were prepared in 2023. See Federal Emergency Management Agency (FEMA), Hazus Estimated Annualized Earthquake Losses for the United States, 2023, https://www.fema.gov/sites/default/files/documents/fema_p-366-hazus-estimated-annualized-earthquake-losses-united-states.pdf.
FEMA's expected annualized loss is based on exposure of buildings, agriculture, and population to the specific hazard times the expected annual frequency of the hazard (in this case, annual expected frequency of an earthquake, which is based on the USGS's probability forecasts) times the historic loss ratio (i.e., the expected loss of buildings, agriculture, and population per earthquake). For more information, see FEMA, "Expected Annualized Losses," https://hazards.fema.gov/nri/expected-annual-loss. FEMA's national risk index for earthquakes estimates the relative risk of a community compared with the rest of the United States for building and population losses due to an earthquake. FEMA compiles data regarding past earthquake locations, previous occurrences, and future probabilities from the USGS National Seismic Hazard Assessment; the Global Significant Earthquake Database produced by the National Oceanic and Atmospheric Administration (NOAA; see NOAA, "NCEI/WDS Global Significant Earthquake Database, 2150 BC to Present," https://www.ncei.noaa.gov/access/metadata/landing-page/bin/iso?id=gov.noaa.ngdc.mgg.hazards:G012153); and Carl W. Stover and Jerry L. Coffman, Seismicity of the United States, 1568-1989 (revised), USGS Professional Paper 1527, 1993, pp. 1-418, https://doi.org/10.3133/pp1527.
U.S. Government Accountability Office (GAO), Need for a National Earthquake Research Program, B-176621, September 11, 1972, pp. 1-81, https://www.gao.gov/assets/b-176621.pdf (hereinafter, GAO, National Earthquake Research, 1972).
GAO, National Earthquake Research, 1972.
For more details about the earthquake, see the USGS, "50 Years Later an Earthquake's Legacy Continues," https://www.usgs.gov/news/featured-story/disaster-helped-nation-prepare-future-earthquakes-remembering-san-fernando.
For an overview of the 1975 M7.3 Haicheng earthquake prediction, see USGS, Earthquake Hazards Program, "Repeating Earthquakes," https://earthquake.usgs.gov/learn/parkfield/eq_predict.php.
GAO, National Earthquake Research, 1972; Robert E. Wallace, Goals, Strategies, and Tasks of the Earthquake Hazards Reduction Program, USGS, USGS Circular 701, 1974; and U.S. Congress, Senate Committee on Commerce, Subcommittee on Oceans and Atmosphere, Earthquake Disaster Mitigation Act of 1975, 94th Cong., 2nd sess., February 19, 1976, No. 94-64, S261-3. Congressional deliberations on earthquake research for risk reduction are recorded in many other hearings after the 1964 M9.2 Anchorage earthquake and before passage of the Earthquake Hazards Reduction Act of 1977 (P.L. 95-124). The particular hearing referenced above covered most aspects of the deliberations, featured witnesses and witness testimony from federal agencies, and included copies of relevant reports.
For more on NEHRP, see CRS Report R43141, The National Earthquake Hazards Reduction Program (NEHRP): Overview and Issues for Congress, by Linda R. Rowan.
The House report that accompanied P.L. 95-124 is U.S. Congress, House Committee on Science and Technology, Earthquake Hazards Reduction Act of 1977, Report to Accompany H.R. 6683, 95th Cong., 1st sess., H. Rept. 95-286, pt. 1, May 11, 1977.
Disaster refers to natural hazards, such as earthquake, flood, hurricane, tornado, landslide, and fire (P.L. 93-288).
Robert E. Wallace, Goals, Strategies and Tasks of the Earthquake Hazards Reduction Program, USGS, USGS Circular 701, 1974.
For a timeline of the development of EEW and ShakeAlert in particular, see Richard Allen, "Earthquake Early Warning Milestones," UC Berkeley, https://rallen.berkeley.edu/research/EEWmilestones.html; and Sara K. McBride et al., "Evidence-Based Guidelines for Protective Actions and Earthquake Early Warning Systems," Geophysics, vol. 87, no. 1 (January-February 2022), pp. WA77-WA102, https://doi.org/10.1190/geo2021-0222.1, Figure 2 (hereinafter McBride, "Protective Actions," 2022).
USGS, ShakeAlert Plan, 2018, p. 6.
Body waves are seismic waves that travel through the Earth's interior. The waves used for earthquake detection for EEW are the primary or compression (P) waves and the secondary or shear (S) waves. P-waves, which travel faster than S-waves, are the first seismic waves to be sensed by instruments deployed at the surface and are the first waves to arrive at a given location. S-waves arrive later than P-waves but carry more energy and cause more intense shaking for a longer time than P-waves. S-waves cause the most damaging ground shaking in most earthquakes that impact communities. An effective EEW system detects the P-waves and determines the earthquake characteristics. This allows an EEW system to provide a warning of high-intensity shaking before the S-waves arrive at locations further away from the earthquake sensing instruments. Surface waves are seismic waves that travel along the surface of the crust; these waves arrive later than the body waves and can contribute to damaging ground shaking, especially for structures that may have been damaged to some extent by the earlier S-waves.
Strauss, "Benefits," 2016.
For example, automatically slowing or stopping a train is one of the most common protective actions to take for an EEW, because the potential to avoid a derailment outweighs the minimal delays caused by stopping a train. EEW systems continue to develop automated or semiautomated alerting for critical structural systems where the application is relatively simple and the cost-benefit calculations and risk-reduction potential are significant.
preparedness/guides/earthquakes.
The Advanced National Seismic System (ANSS) supports basic and applied research to understand and define the structure of the Earth beneath the surface, including mapping faults and understanding earthquakes. ANSS activities contribute to the research and development of EEW. ANSS consists of a backbone network of almost 100 seismic stations distributed throughout the United States, the USGS National Earthquake Information Center, the National Strong Ground Motion network, and 15 regional seismic networks. See the USGS, "ANSS – Advanced National Seismic System," https://www.usgs.gov/programs/earthquake-hazards/anss-advanced-national-seismic-system.
USGS, ShakeAlert Plan, 2018.
FEMA, "Hazard Mitigation Assistance Grants," https://www.fema.gov/grants/mitigation; and FEMA, "Building Resilient Infrastructure and Communities," https://www.fema.gov/grants/mitigation/building-resilient-infrastructure-communities.
FEMA mitigation grants may not support any operations and maintenance activities for ShakeAlert. FEMA may support only improvements to ShakeAlert, because the authorization requires FEMA to support EEW capabilities that enable end-user notification. FEMA consulted with the USGS and determined that ShakeAlert is the only system that enables end-user notification. FEMA, "Disaster Recovery Reform Act and Earthquake Early Warning Systems," fact sheet, September 30, 2020, https://www.fema.gov/sites/default/files/2020-09/fema_drra-earthquake-early-warning-systems_fact-sheet_September-2020.pdf.
NRC, Precise Geodetic Infrastructure, 2010 and NASA, Earth Science, Applied Sciences, "Supporting Earthquake Response and Recovery," https://appliedsciences.nasa.gov/what-we-do/disasters/earthquakes.
Correspondence between CRS and USGS, December 12, 2024.
USGS, ShakeAlert Plan, 2018.
USGS, ShakeAlert Plan, 2018; and correspondence between CRS and the USGS, January 12, 2022.
Based on research, development, and testing, the data analysis may be improved by adding the raw geodetic data and the Geodetic First Approximation of Size and Timing—Peak Ground Displacement (GFAST-PGD) algorithm into the operational data analysis system. See Jessica R. Murray et al., "Development of a Geodetic Component for the U.S. West Coast Earthquake Early Warning System," Seismological Research Letters, vol. 89, no. 6 (October 3, 2018), pp. 2322-2336, https://doi.org/10.1785/0220180162.
USGS, ShakeAlert Plan, 2018.
USGS, ShakeAlert Plan, 2018, pp. 18-20.
See National Academies of Sciences, Engineering, and Medicine, Emergency Alert and Warning Systems: Current Knowledge and Future Research, 2018, https://doi.org/10.17226/24935.
For more details about the Integrated Public Alert Warning System, see FEMA, "Integrated Public Alert and Warning System," https://www.fema.gov/emergency-managers/practitioners/integrated-public-alert-warning-system. See also, CRS Report R48363, The Integrated Public Alert and Warning System (IPAWS): Primer and Issues for Congress, by Amanda H. Peskin.
Some individuals or institutions that are close to the earthquake's epicenter may receive no warning or preparation times of less than 10 seconds, which is not enough time to take action. Other individuals or institutions that are far from the earthquake's epicenter may receive one to two minutes of preparation time. For example, many of the most damaging earthquakes in Mexico start on the offshore subduction zone near the western coastline and are hundreds of miles away from large cities. When a subduction zone earthquake is detected on the west coast, Mexico City receives an EEW before the seismic waves travel hundreds of miles to the city, so that people in the city have one to two minutes to prepare for intense shaking to arrive. USGS, Expected Warning Times, 2021; Sarah E. Minson et al., "The Limits of Earthquake Early Warning: Timeliness of Ground Motion Estimates," Science Advances, vol. 4, no. 3 (2018), https://doi.org/10.1126/sciadv.aaq0504 (hereinafter Minson, "Limits of EEW," 2018); and Gerardo Suarez et al., "A Dedicated Seismic Early Warning Network: The Mexican Seismic Alert System (SASMEX)," Seismological Research Letters, vol. 89, no. 2A (March/April 2018), pp. 382-391, https://doi.org/10.1785/0220170184 (hereinafter SASMEX, 2018).
USGS, Expected Warning Times, 2021, p. 3.
USGS, ShakeAlert Plan, 2018.
USGS, ShakeAlert Plan, 2018, pp. 20-21; and Minson, "Limits of EEW," 2018.
EEWs distributed via WiFi or cellular networks commonly arrive in 1-10 seconds, but various apps are still testing the scaling to large numbers of users. WiFi technology uses radiofrequency waves to transmit information wirelessly. WiFi networks work only within a limited distance and require a modem connected to a wireless router or wireless gateway. Cellular networks use cellular signals to transmit information. Cellular networks work over larger distances where there are enough cellular towers to transmit the cellular signals from towers to devices. The WEA system can deliver EEWs as fast as 4 seconds based on recent tests, but many individuals receive the EEWs after more than 10 seconds or not at all. USGS, ShakeAlert Plan, 2018; and USGS, Expected Warning Times, 2021, p.3.
USGS, Expected Warning Times, 2021, p. 3.
See FEMA, "Wireless Emergency Alerts," https://www.fema.gov/emergency-managers/practitioners/integrated-public-alert-warning-system/public/wireless-emergency-alerts. See FEMA's IPAWS website at https://www.fema.gov/emergency-managers/practitioners/integrated-public-alert-warning-system. See CRS Report R48363, The Integrated Public Alert and Warning System (IPAWS): Primer and Issues for Congress, by Amanda H. Peskin.
USGS, ShakeAlert Plan, 2018.
Federal Communications Commission, Report: August 11, 2021, Nationwide WEA Test—Wireless Emergency Alerts, December 2021, https://www.fcc.gov/document/fcc-releases-report-nationwide-wea-test, p.5 (hereinafter FCC, WEA Test, 2021).
The more advanced geotargeted alerts require providers that participate in the WEA program to send alerts to the targeted area with no more than a 0.1mile overshoot. FCC, WEA Test, 2021
FCC, WEA Test, 2021. See also Sara K. McBride et al., "Latency and geofence testing of wireless emergency alerts intended for the ShakeAlert earthquake early warning system for the West Coast of the United States of America," Safety Science, vol. 157, no. 105898 (2023), https://doi.org/10.1016/j.ssci.2022.105898 (Hereinafter McBride, Testing ShakeAlert, 2023).
USGS, ShakeAlert Plan, 2018, pp. 23-24.
FCC, Report: October 4, 2023 Nationwide Emergency Alert Test, June 2024, https://docs.fcc.gov/public/attachments/DOC-403500A1.pdf.
The major transportation companies that are License to Operate (LtO) partners using ShakeAlert are San Francisco Bay Area Rapid Transit (BART), with 411,000 average weekday passengers (pre-COVID); Los Angeles Metropolitan Transit Authority (LA Metro), with an average weekday ridership of 344,176; and the Southern California Regional Rail Authority (Metrolink), which averages about 40,000 boardings on a typical weekday. Correspondence between CRS and the USGS, January 12, 2022.
Correspondence between CRS and the USGS, January 12, 2022.
CalOES, "Cal OES and UC Berkeley Announce New MyShake Tools for Early Earthquake Notification," https://news.caloes.ca.gov/cal-oes-and-uc-berkeley-announce-new-myshake-tools-for-early-earthquake-notification.
Angela I. Lux et al., "Status and Performance of the ShakeAlert Earthquake Early Warning System: 2019-2023," Bulletin of the Seismological Society of America, vol. 114, no. 6 (August 2024), pp. 3041-3062, doi: 10.1785/0120230259 (hereinafter Lux, 2024). ShakeAlert integrated geodetic data into its operational system after the review period listed in this reference, so the status and performance overview does not consider ShakeAlert performance using geodetic data. See also CalOES, "California Earthquake Early Warning Advisory Board Meeting, September 11, 2024," https://www.caloes.ca.gov/wp-content/uploads/Earthquake-Tsunami-Volcano/Documents/Cal-OES-EEW-Presentation.pdf for the latest update on ShakeAlert in California. See also YouTube, "EEW Advisory Board," https://www.youtube.com/watch?v=xmrNYON1Kuw.
Lux, 2024. The geodetic data algorithms and the geodetic observing network was not part of the operational ShakeAlert system during the review period from October 17, 2019, to September 1, 2023. According to the review, the addition of the geodetic algorithms may lead to improved magnitude estimates and may provide redundancy for the system should any problems arise with the seismic stations.
Lux, 2024.
Lux, 2024.
USGS, ShakeAlert Plan, 2018; USGS, Expected Warning Times, 2021, p.3 and FEMA National Advisory Council, Modernizing the Nation's Public Alert and Warning System, February 15, 2019, https://www.hsdl.org/?view&did=826793.
Lux, 2024.
FEMA National Advisory Council, Modernizing the Nation's Public Alert and Warning System, February 15, 2019, https://www.hsdl.org/?view&did=826793, p. 7.
USGS, ShakeAlert Plan, 2018; and USGS, Expected Warning Times, 2021, p. 3.
FEMA National Advisory Council, Modernizing the Nation's Public Alert and Warning System, February 15, 2019, https://www.hsdl.org/?view&did=826793, p. 7.
USGS, ShakeAlert Plan, 2018.
USGS, ShakeAlert Plan, 2018; and correspondence between CRS and the USGS, January 12, 2022.
Allen and Melgar, "EEW Advances," 2019, p. 364.
Correspondence between CRS and the USGS, January 12, 2022.
As of August 19, 2024, there have been 3,529,922 downloads of the MyShake app in California. CalOES, "California Earthquake Early Warning Advisory Board Meeting, September 11, 2024," https://www.caloes.ca.gov/wp-content/uploads/Earthquake-Tsunami-Volcano/Documents/Cal-OES-EEW-Presentation.pdf for the latest update on ShakeAlert in California. See also YouTube, "EEW Advisory Board," https://www.youtube.com/watch?v=xmrNYON1Kuw.
iOS is a mobile operating system developed by Apple for Apple mobile devices. iOS was formerly known as iPhone OS. OS stands for operating system.
114 Government of California, "California's First-in-the-Nation Earthquake Early Warning System Notified Millions Ahead of Quake," https://www.gov.ca.gov/2024/08/07/californias-first-in-the-nation-earthquake-warning-system-notified-millions-ahead-of-quake.
McBride, "Protective Actions," 2022.
Julia S. Becker et al., "Earthquake Early Warning in Aotearoa New Zealand: A Survey of Public Perspectives to Guide Warning System Development," Humanities and Social Sciences Communications, vol. 7, no. 138 (2020), https://doi.org/10.1057/s41599-020-00613-9; and Kazuya Nakayachi et al., "Residents' Reaction to Earthquake Early Warnings in Japan," Risk Analysis, vol. 39, no. 8 (2019), pp. 1723-1740, https://doi.org/10.1111/risa.13306.
Correspondence between CRS and the USGS, January 12, 2022.
USGS, ShakeAlert Plan, 2018; and correspondence between CRS and the USGS, January 12, 2022. For more information about ANSS, see footnote 53.
See CRS Report R43141, The National Earthquake Hazards Reduction Program (NEHRP): Overview and Issues for Congress, by Linda R. Rowan.
Earthquake Early Warning System, Senate Bill No. 135 (SB-135, Chapter 342, Statutes of 2013), California Government Code Section 8587.8, https://leginfo.legislature.ca.gov/faces/billTextClient.xhtml?bill_id=201320140SB135
Earthquake Safety: Statewide Earthquake Early Warning Program and System, Senate Bill No. 438 (Chapter 803, Statutes of 2016), California Government Code Section 8587.8, 8587.11, and 8587.12, https://leginfo.legislature.ca.gov/faces/billTextClient.xhtml?bill_id=201520160SB438
Oregon Military Department, Office of Emergency Management, "ShakeAlert in Oregon," https://www.oregon.gov/oem/hazardsprep/pages/orshakealert.aspx.
Washington Military Department, Emergency Management, "Alert and Warning Notifications, ShakeAlert Earthquake Early Warning," https://mil.wa.gov/alerts.
ShakeAlert.org, "Earthquake Early Warning in US and Canada," https://www.earthquakescanada.nrcan.gc.ca/eew-asp/system-en.php
Government of Canada, "Canadian Earthquake Early Warning System," https://www.earthquakescanada.nrcan.gc.ca/eew-asp/system-en.php.
USGS, ShakeAlert Plan, 2018. Mexico's SASMEX began sending earthquake early warning alerts to Mexico City in 1991. SASMEX is different from ShakeAlert, it is not possible to integrate the two systems, and SASMEX does not cover Baja California, Mexico. Gerardo Suarez, "The Seismic Early Warning System of Mexico (SASMEX): A Retrospective View and Future Challenges," Frontiers in Earth Sciences, February 15, 2022, p. https://doi.org/10.3389/feart.2022.827236.
USGS, ShakeAlert Plan, 2018.
CRS correspondence with USGS on March 10, 2025. See also USGS, Budget Justifications and Performance Information Fiscal Year 2025, 2024, https://www.doi.gov/media/document/fy-2025-u-s-geological-survey-greenbook.
Although NSF is not officially a ShakeAlert partner, it contributes funding that supports research and infrastructure that advances aspects of ShakeAlert. It does so through research grants and cooperative agreements to universities, the EarthScope Consortium, the Statewide California Earthquake Center and others.
Cal OES, California Earthquake Early Warning Business Plan Update, 2021, p. 12, https://www.caloes.ca.gov/EarthquakeTsunamiVolcanoProgramsSite/Documents/CEEWS%20Business%20Plan%20Update%20Final.pdf.
USGS, ShakeAlert Plan, 2018, p. 41.
USGS, ShakeAlert Plan, 2018.
Gemma Cremen and Carmine Galasso, "Earthquake Early Warning: Recent Advances and Perspectives," Earth Science Reviews, vol. 205 (June 2020), pp. 1-15, https://doi.org/10.1016/j.earscirev.2020.103184.
SASMEX, 2018.
Japan uses a geodetic network on land for tsunami early warning but not for earthquake early warning. Shin Aoi et al., "MOWLAS: NIED Observation Network for Earthquake, Tsunami, and Volcano," Earth, Planets, and Space, vol. 72, no. 126 (2020), https://earth-planets-space.springeropen.com/articles/10.1186/s40623-020-01250-x
Yuki Kodera et al., "Developments of the Nationwide Earthquake Early Warning System in Japan After the 2011 Mw9.0 Tohoku-Oki Earthquake," Frontiers in Earth Science, vol. 9 (October 3, 2021), https://doi.org/10.3389/feart.2021.726045.
Benjamin A. Brooks et al., "Robust Earthquake Early Warning at a Fraction of the Cost: ASTUTI Costa Rica," AGU Advances, vol. 2 (May 2021), e2021AV000407, pp. 1-17, https://doi.org/10.1029/2021AV000407 (hereinafter Brooks et al., "Robust Earthquake Early Warning").
Brooks et al., "Robust Earthquake Early Warning."
As noted earlier, cell phones have miniature accelerometers that are similar to miniature seismic instruments and miniature Global Navigation Satellite System (GNSS) receivers that are similar to geodetic instruments. The receivers also provide location. The Google app analyzes the signals from these miniature instruments in many cell phones to determine if an earthquake has been detected and its location.
BBC, "Google Alert Failed to Warn People of Turkey Earthquake," https://www.bbc.com/news/technology-66316462, and Androidcentral, "Google Shuts Down Its Earthquake Alerts in Brazil After a Warning Failure," https://www.yahoo.com/news/google-shuts-down-earthquake-alerts-075435525.html.
EarthScope Consortium, "Distributed Acoustic Sensing," https://www.earthscope.org/what-is/das. Oak Ridge National Laboratory, "CyberShake study uses Summit supercomputer to investigate earthquake hazards," https://www.ornl.gov/news/cybershake-study-uses-summit-supercomputer-investigate-earthquake-hazards. Hisahiko Kubo, Makoto Naoi, and Masayuki Kano, "Recent advances in earthquake seismology using machine learning," Earth, Planets and Space, vol. 76, no. 36 (February 28, 2024), https://doi.org/10.1186/s40623-024-01982-0 and Robert E. Anthony et al., "Preface to Focus Section on New Frontiers and Advances in Global Seismology," Seismological Research Letters, vol. 953 (May, 2024), https://doi.org/10.1785/0220240092 and articles in this special section.
USGS, "Products," https://www.usgs.gov/programs/earthquake-hazards/products and USGS, Earthquake Hazards Program, External Grants, "External Grants," https://earthquake.usgs.gov/cfusion/external_grants/research.cfm
NEHRP, "Grants and Contracts," https://nehrp.gov/contracts/index.htm.
Lux, 2024.
USGS, ShakeAlert Plan, 2018 and Lux, 2024.
GAO, "Earthquakes: Progress Made to Implement Early Warning System, but Actions Needed to Improve Program Management," https://www.gao.gov/products/gao-21-129 and GAO, "Earthquakes: Opportunities Exist to Further Assess Risk, Build Resilience, and Communicate Research," https://www.gao.gov/products/gao-22-105016.
USGS, "U.S. Geological Survey Earthquake Hazards Program Decadal Science Strategy, 2024-33," https://www.usgs.gov/publications/us-geological-survey-earthquake-hazards-program-decadal-science-strategy-2024-33.
See USGS response to GAO recommendations: GAO, "Earthquakes: Progress Made to Implement Early Warning System, but Actions Needed to Improve Program Management," https://www.gao.gov/products/gao-21-129.
GAO, "Earthquakes: Opportunities Exist to Further Assess Risk, Build Resilience, and Communicate Research," https://www.gao.gov/products/gao-22-105016.
NEHRP, Strategic Plan for the National Earthquake Hazards Reduction Program, Fiscal Years 2022-2029, April 2023, https://nehrp.gov/pdf/FY2022-29%20NEHRP%20Strategic%20Plan%20-%20Post%20Version.pdf.
NOAA, "National Geodetic Survey," https://geodesy.noaa.gov/INFO/WhatWeDo.shtml.
Explanatory Statement, Division G–Department of the Interior, Environment, and Related Agencies Appropriations Act, FY2022, to accompany H.Rept. 117-83 for P.L. 117-103. Cecily J. Wolfe et al., Phase 1 Technical Implementation Plan for the Expansion of the ShakeAlert Earthquake Early Warning System to Alaska, USGS, Open-File Report 2025-1003, 2025, https://doi.org/10.3133/ofr20251003.
For example, see FEMA National Advisory Council, Modernizing the Nation's Public Alert and Warning System, February 15, 2019, https://www.hsdl.org/?view&did=826793 and the recent contract awarded to AT&T to modernize FEMA's IPAWS, AT&T Communications, "FEMA Awards AT&T 4 EIS Contracts Valued at $167M/5-Years to Modernize Its Communications Capabilities," press release, February 15, 2022, https://www.prnewswire.com/news-releases/fema-awards-att-4-eis-contracts-valued-at-167m5-years-to-modernize-its-communications-capabilities-301482531.html.
See Cliff Mass, "A Critical Gap in Tornado Warning Technology: Lessons of the Recent Tornado Outbreak," Cliff Mass Weather Blog, December 12, 2021, https://cliffmass.blogspot.com/2021/12/a-critical-gap-in-tornado-warning.html.
USGS, ShakeAlert Plan, 2018, pp. 30-32.
NEHRP, "Grants and Contracts," https://nehrp.gov/contracts/index.htm.
U.S. Geological Survey (USGS), "Magnitude Types," https://www.usgs.gov/programs/earthquake-hazards/magnitude-types.
For more information about the 2011 M9.1 Tohoku earthquake and the magnitude underestimate, see Richard M. Allen and Diego Melgar, "Earthquake Early Warning: Advances, Scientific Challenges and Societal Needs," Annual Review of Earth and Planetary Sciences, vol. 47 (2019), pp 361-388 (see p. 374), https://doi.org/10.1146/annurev-earth-053018-060457 (hereinafter, Allen and Melgar, "EEW Advances," 2019) and NRC, Precise Geodetic Infrastructure, 2010.
For more details, see USGS, "The Modified Mercalli Intensity Scale," https://www.usgs.gov/programs/earthquake-hazards/modified-mercalli-intensity-scale.
Liquefaction occurs when earthquake-induced ground shaking causes loose, weak, or water-saturated soils or rocky materials to lose their strength. When liquefaction happens around structures, such as buildings or bridges, these structures can be damaged or collapse because the foundations of these structures are no longer supported. For more information about liquefaction, see the USGS, "What Is Liquefaction?," https://www.usgs.gov/faqs/what-liquefaction.
See the USGS, "At What Depth Do Earthquakes Occur? What Is the Significance of the Depth?," https://www.usgs.gov/faqs/what-depth-do-earthquakes-occur-what-significance-depth.
See Occupational Safety and Health Administration "Earthquakes Guide," https://www.osha.gov/emergency-preparedness/guides/earthquakes for more details.