Order Code RL33861
Earthquakes: Risk, Monitoring,
Notification, and Research
Updated January 16, 2008
Peter Folger
Specialist in Energy and Natural Resources Policy
Resources, Science, and Industry Division
Earthquakes: Risk, Monitoring,
Notification, and Research
Summary
Close to 75 million people in 39 states face some risk from earthquakes.
Seismic hazards are greatest in the western United States, particularly California,
Alaska, Washington, Oregon, and Hawaii. The Rocky Mountain region, a portion
of the central United States known as the New Madrid Seismic Zone, and portions
of the eastern seaboard, particularly South Carolina, also have a relatively high
earthquake hazard. Compared to the loss of life in other countries, relatively few
Americans have died as a result of earthquakes over the past 100 years. The United
States, however, faces the possibility of large economic losses from earthquake-
damaged buildings and infrastructure. Until Hurricane Katrina in 2005, the 1994
Northridge (CA) earthquake was the costliest natural catastrophe to strike the United
States; some damage estimates were $26 billion (in 2005 dollars). Estimates of total
loss from a hypothetical earthquake of magnitude more than 7.0 reach as high as
$500 billion for the Los Angeles area.
Given the potentially huge costs associated with a severe earthquake, an ongoing
issue for Congress is whether the federally supported programs aimed at reducing
U.S. vulnerability to earthquakes are an adequate response to the earthquake hazard.
Under the National Earthquake Hazards Reduction Program (NEHRP), four federal
agencies have responsibility for long-term earthquake risk reduction: the U.S.
Geological Survey (USGS), the National Science Foundation (NSF), the Federal
Emergency Management Agency (FEMA), and the National Institute of Standards
and Technology (NIST). They variously assess U.S. earthquake hazards, send
notifications of seismic events, develop measures to reduce earthquake hazards, and
conduct research to help reduce overall U.S. vulnerability to earthquakes.
Congress established NEHRP in 1977, and its early focus was on research that
would lead to an improved understanding of why earthquakes occur and to an ability
to predict their occurrence precisely. Congress most recently reauthorized NEHRP
in 2004 (P.L. 108-360), and designated NIST as the lead agency, to create better
synergy among the agencies and improve the program. Understanding has improved
about why and where earthquakes occur; however, reliably predicting the precise date
and time an earthquake will occur is not yet possible. Research may eventually lead
to an ability to predict earthquakes, but the focus of NEHRP now has shifted towards
improving the nation’s ability to prepare for earthquakes and to minimize losses
when an earthquake occurs.
The USGS has responsibility for conducting targeted research to improve the
basic scientific understanding of earthquake processes. NSF supports fundamental
research — it distributes research grants and coordinates programs — that could lead
to a better understanding of crustal processes that cause earthquakes around the
globe. NSF also supports research to improve the safety and performance of
buildings and structures. FEMA assists other agencies and private-sector groups to
prepare and disseminate building codes and practices for structures. NIST — in
addition to being lead agency for NEHRP — supports development of performance-
based seismic engineering tools and promotes their commercial application.
Contents
Earthquake Hazards and Risk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Advanced National Seismic System (ANSS) . . . . . . . . . . . . . . . . . . . . 9
National Strong-Motion Project (NSMP) . . . . . . . . . . . . . . . . . . . . . . 10
Global Seismic Network (GSN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Detection, Notification, and Warning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
National Earthquake Information Center (NEIC) . . . . . . . . . . . . . . . . 12
ShakeMap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
National Earthquake Hazards Reduction Program (NEHRP) . . . . . . . . . . . 14
Mitigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Research — Understanding Earthquakes . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
U.S. Geological Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
National Science Foundation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Additional Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
List of Figures
Figure 1. Earthquake Hazard in the United States . . . . . . . . . . . . . . . . . . . . . . . . 2
Figure 2. Histogram of the Number of Earthquakes in the United States
from 2000 to 2007 by Magnitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Figure 3. Example of a ShakeMap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
List of Tables
Table 1. 26 Urban Areas Facing Significant Seismic Risk . . . . . . . . . . . . . . . . . . 3
Table 2. Earthquakes Responsible for Most U.S. Fatalities Since 1970 . . . . . . . . 5
Table 3. The 10 Most Damaging Earthquakes in the United States . . . . . . . . . . . 6
Table 4. U.S. Cities With Estimated Annualized Earthquake Losses of
More than $10 Million . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Table 5. Authorized and Enacted Funding for NEHRP . . . . . . . . . . . . . . . . . . . 16
Earthquakes: Risk, Monitoring,
Notification, and Research
The 1994 Northridge (CA) earthquake caused as much as $26 billion (in 2005
dollars) in damage, according to one estimate, and was one of the costliest natural
disasters to strike the United States. The Federal Emergency Management
Administration (FEMA) has estimated that earthquakes cost the United States over
$4 billion per year. Some cost estimates of a single, large earthquake striking the Los
Angeles area range as high as $500 billion.
Under the National Earthquake Hazards Reduction Program (NEHRP), the
federal government supports efforts to assess and monitor earthquake hazards and
risk in the United States. Four federal agencies, responsible for long-term earthquake
risk reduction, coordinate their activities under NEHRP: the U.S. Geological Survey
(USGS), the National Science Foundation (NSF), FEMA, and the National Institute
of Standards and Technology (NIST). Congress reauthorized NEHRP in 2004 (P.L.
108-360).
Given the potentially huge costs associated with a large, damaging earthquake
in the United States, an ongoing issue for Congress is whether the federally supported
earthquake programs are adequate for the earthquake risk. This report describes
estimates of earthquake hazards and risk in the United States, the current federal
programs that support earthquake monitoring and that provide notification after a
seismic event, and the programs that support mitigation and research aimed at
reducing U.S. vulnerability to earthquakes.
Earthquake Hazards and Risk
All 50 states are vulnerable to earthquake hazards, although risks vary greatly
across the country. Seismic hazards are greatest in the western continental United
States, particularly California, Washington, Oregon, and Alaska and Hawaii (see
Figure 1). Alaska is the most earthquake-prone state, experiencing a magnitude 7
earthquake1 almost every year and a magnitude 8 earthquake every 14 years on
1 Magnitude is a number that characterizes the relative size of an earthquake. Earthquake
magnitude is often reported using the Richter scale (magnitudes in this report are generally
consistent with the Richter scale). Richter magnitude is calculated from the strongest
seismic wave recorded from the earthquake, and is based on a logarithmic (base 10) scale:
for each whole number increase in the Richter scale, the ground motion increases by ten
times. The amount of energy released per whole number increase, however, goes up by a
factor of 32. The moment magnitude scale is another expression of earthquake size, or
energy released during an earthquake, that roughly corresponds to the Richter magnitude
and is used by most seismologists because it more accurately describes the size of very large
earthquakes. Intensity is a measure of how much shaking occurred at a site based on
(continued...)
CRS-2
average. California has more citizens and infrastructure at risk than any other state
because of the state’s frequent seismic activity combined with its high population.
Figure 1. Earthquake Hazard in the United States
Source: USGS, “Conterminous States Probabilistic Maps & Data” (modified by CRS),
at [http://earthquake.usgs.gov/research/hazmaps/products_data/images/nshm_us02.gif].
Figure 1 also shows relatively high earthquake hazard in the Rocky Mountain
region, portions of the eastern seaboard — particularly South Carolina — and a part
of the central United States known as the New Madrid Seismic Zone (discussed
below). Other portions of the eastern and northeastern United States are also
vulnerable to moderate seismic hazard. According to the USGS, 75 million people
in 39 states are subject to significant risk. During the period 1975-1995, only four
states did not experience detectable earthquakes: Florida, Iowa, North Dakota, and
Wisconsin.
As Figure 1 indicates, good information exists on where earthquakes are likely
to occur and how severe the earthquake magnitude and resulting ground shaking are
likely to be. The map in Figure 1 depicts the potential shaking hazard from future
earthquakes. It is based on the frequency at which earthquakes occur in different
areas and how far the strong shaking extends from the source of the earthquake. In
1 (...continued)
observations and amount of damage. Intensity is usually reported on the Modified Mercalli
Intensity Scale as a Roman numeral ranging from I (not felt) to XII (total destruction).
CRS-3
Figure 1, the hazard levels indicate the potential ground motion — expressed as a
percentage of the acceleration due to gravity (g) — with up to a 1 in 10 chance of
being exceeded over a 50-year period.
Shaking-hazards maps, such as the one in Figure 1, are often combined with
other data, such as the strength of existing buildings, to estimate possible damage in
an area following an earthquake. The combination of seismic risk, population, and
vulnerable infrastructure can help improve the understanding of which urban areas
across the United States face risks from earthquake hazards that may not be
immediately obvious from the probability maps of shaking hazards alone. The USGS
has identified 26 urban areas that face a significant seismic risk from the combination
of population and severity of shaking. Table 1 lists those areas at greatest risk.
Table 1. 26 Urban Areas Facing Significant Seismic Risk
(alphabetically by state for cities with at least 300,000 people)
State
City
State
City
Alaska
Anchorage
Nevada
Las Vegas
California
Fresno
Nevada
Reno
California
Los Angeles
New Mexico
Albuquerque
California
Sacramento
New York
New York
California
Salinas
Oregon
Eugene-Springfield
California
San Diego
Oregon
Portland
California
San Francisco-Oakland
Puerto Rico
San Juan
California
Santa Barbara
South Carolina
Charleston
California
Stockton-Lodi
Tennessee
Chattanooga-Knoxville
Idaho
Boise
Tennessee
Memphis
Indiana
Evansville
Utah
Provo-Orem
Massachusetts
Boston
Utah
Salt Lake City
Missouri
St. Louis
Washington
Seattle
Sources: USGS Fact Sheet 2006-3016 (March 2006); USGS Circular 1188, Table 3.
Note: These areas are identified using a population-based risk factor based on 1999
population data. (William Leith, ANSS Coordinater, USGS, Reston, VA, telephone
conversation, Nov. 15, 2006).
The USGS estimates that several million earthquakes occur worldwide each
year, but the majority are of small magnitude or occur in remote areas, and are not
detectable. More earthquakes are detected each year as more seismometers2 are
installed in the world, but the number of large earthquakes (magnitude greater than
6.0)3 has remained relatively constant. Between 2000 and 2007 there were between
2,261 and 3,876 earthquakes in the United States per year, according to the National
Earthquake Information Center (NEIC). (See Figure 2.)
2 Seismometers are instruments that measure and record the size and force of seismic waves,
essentially sound waves radiated from the earthquake as it ruptures. Seismometers generally
consist of a mass attached to a fixed base. During an earthquake, the base moves and the
mass does not, and the relative motion is commonly transformed into an electrical voltage
that is recorded. A seismograph usually refers to the seismometer and the recording device,
but the two terms are often used interchangeably.
3 See USGS “Earthquakes Facts and Statistics” at [http://neic.usgs.gov/neis/eqlists/eqstats.
html#table_2].
CRS-4
Figure 2. Histogram of the Number of Earthquakes in the United
States from 2000 to 2007 by Magnitude
2000
1800
1600
1400
es
1200
uak
1000
rthq
a
f E
800
o
er
b
600
400
Num
200
0
0.1 to 0.9
1.0 to 1.9
2.0 to 2.9
3.0 to 3.9
4.0 to 4.9
5.0 to 5.9
6.0 to 6.9
Magnitude
2000
2001
2002
2003
2004
2005
2006
2007
Source: USGS, “Earthquake Facts and Statistics,” at [http://neic.usgs.gov/neis/eqlists/eqstats.html];
data as of Jan. 3, 2008.
Note: Earthquakes greater than magnitude 7.0 are not shown.
As Figure 2 shows, about 98% of earthquakes detected each year by the NEIC
are smaller than magnitude 5.0; only 60 earthquakes exceeded magnitude 6.0 for the
eight-year period (less than 0.3% of the total earthquakes detected) for an average of
slightly more than seven earthquakes per year of at least 6.0 magnitude.
Large earthquakes, although infrequent, cause the most damage and are
responsible for most earthquake-related deaths. Over the past 100 years, relatively
few Americans have died as a result of earthquakes, compared to citizens in other
countries. The great San Francisco earthquake of 1906 claimed an estimated 3,000
lives, as a result of both the earthquake and subsequent fires.4 Since 1970, three
major earthquakes in the United States were responsible for 188 of the 212 total
earthquake-related fatalities (see Table 2).
Since 2000, only two deaths directly caused by earthquakes have occurred in the
United States, both associated with falling debris in Paso Robles (CA) during the
December 22, 2003, San Simeon earthquake of magnitude 6.5. In contrast,
earthquakes are directly or indirectly responsible for more than 430,000 fatalities in
other countries since 2000. More than half of those estimated deaths resulted from
the December 2004 Indonesian earthquake of magnitude 9.1 and the resulting
tsunami.
4 Estimates of earthquake-related fatalities may vary and an exact tally of deaths and injuries
is rare. For more information on the difficulties of counting earthquake-related deaths and
injuries, see [http://earthquake.usgs.gov/regional/world/casualty_totals.php].
CRS-5
Table 2. Earthquakes Responsible for
Most U.S. Fatalities Since 1970
Date
Location
Magnitude
Deaths
February 9, 1971
San Fernando Valley, CA
6.6
65
October 18, 1989
Loma Prieta, CA
6.9
63
January 17, 1994
Northridge, CA
6.7
60
Source: USGS, [http://earthquake.usgs.gov/regional/states/us_deaths.php].
Note: Other sources report different numbers of fatalities associated with the Northridge
earthquake.
The 1994 Northridge earthquake was the nation’s most damaging earthquake
in the past 100 years, preceded five years earlier by the second most costly
earthquake — Loma Prieta. Table 3 shows the 10 costliest U.S. earthquakes
according to one estimate of insured and uninsured losses. Comparing losses
between different earthquakes, and between earthquakes and other disasters such as
hurricanes, can be difficult because of the different ways losses are calculated.
Calculations may include a combination of insured losses, uninsured losses, and
estimates of lost economic activity. For example, insured losses from Hurricane
Katrina in 2005 — mainly property — may be $41 billion, according to one
estimate.5 Total property damage would rise if uninsured property were included;
and including interrupted economic activity in the calculation could bring the total
loss for Hurricane Katrina to $100 billion.6
The United States faces potentially large total losses due to earthquake-caused
damage to buildings and infrastructure and lost economic activity. As urban
development continues in earthquake-prone regions in the United States, concerns
are increasing about the exposure of the built environment, including utilities and
transportation systems, to potential earthquake damage.7 One estimate of loss from
a severe earthquake in the Los Angeles area is over $500 billion. An even higher
estimate — approximately $900 billion — includes damage to the heavily populated
central New Jersey-Philadelphia corridor if a 6.5 magnitude earthquake occurred
along a fault lying between New York City and Philadelphia.8
5 Insurance Information Institute, [http://www.iii.org/media/facts/statsbyissue/hurricanes/].
Loss estimates are in 2005 dollars.
6 Risk Management Solutions (RMS), Newark, CA, press release (Sept. 2, 2005), at
[http://www.rms.com/NewsPress/PR_090205_HUKatrina.asp].
7 FEMA Publication 366, HAZUS 99 Estimated Annualized Earthquake Losses for the
United States (February 2001). Hereafter referred to as FEMA 366.
8 A. M. Best Company Inc., 2006 Annual Earthquake Study: $100 Billion of Insured Loss
in 40 Seconds (Oldwick, NJ: A.M. Best Company, 2006), p. 12. The A. M. Best report
includes estimates from catastrophe-modeling companies of predicted damage from
hypothetical earthquakes in Los Angeles, the Midwest, the Northeast, and Japan. The report
(continued...)
CRS-6
Table 3. The 10 Most Damaging Earthquakes
in the United States
Year
Location
Magnitude
2005 constant $
1994
Northridge, CA
6.7
$26 billiona
1989
Loma Prieta, CA
6.9
$11 billion
1964
Anchorage, AK
9.2
$3.1 billion
1971
San Fernando, CA
6.5
$2.7 billion
2001
Nisqually, WA
6.8
$2.5 billion
1987
Whittier Narrows, CA
5.9
$615 million
1933
Long Beach, CA
6.3
$600 million
1953
Kern County, CA
7.5
$440 million
1992
Landers, CA
7.6
$130 million
1992
Cape Mendocino, CA
7.1
$92 million
Source: Insurance Information Institute, at [http://www.iii.org/media/facts/statsbyissue/
earthquakes/].
Note: Includes insured and uninsured losses.
a Estimates for total losses resulting from the Northridge earthquake vary; the
Congressional Budget Office estimated $43 billion in total losses (1999 dollars). See
Federal Reinsurance for Disasters, Congressional Budget Office (September 2002), p.
19.
Some studies and techniques combine seismic risk with the value of the building
inventory9 and income losses (e.g., business interruption, wage, and rental income
losses) in cities, counties, or regions across the country to provide estimations of
economic losses from earthquakes. One report10 calculates that the annualized loss
from earthquakes nationwide is $4.4 billion, with California, Oregon, and
Washington accounting for $3.7 billion (84%) of the U.S. total estimated annualized
loss. Table 4 shows cities with estimated annualized U.S. earthquake losses over
$10 million. Annualized earthquake loss (AEL) addresses two components of
8 (...continued)
cites an estimate by one such company, Risk Management Solutions, that a hypothetical 7.4
magnitude event along the Newport-Inglewood Fault near Los Angeles would cause $549
billion in total property damage. A hypothetical 6.5 magnitude earthquake along a fault
between Philadelphia and New York City would produce $901 billion in total loss,
according to an RMS estimate.
9 Building inventory refers to four main inventory groups: (1) general building stock, (2)
essential and high potential loss facilities, (3) transportation systems, and (4) utility systems
(FEMA 366).
10 FEMA 366.
CRS-7
seismic risk: the probability of ground motion and the consequences of ground
motion. It enables comparison between different regions with different seismic
hazards and different building construction types and quality. For example,
earthquake hazard is higher in the Los Angeles area than in Memphis, but the general
building stock in Los Angeles is more resistant to the effects of earthquakes. The
AEL annualizes the expected losses by averaging them by year.
Table 4. U.S. Cities With Estimated Annualized
Earthquake Losses of More than $10 Million
(in millions)
Rank
Metro area
AEL
Rank
Metro area
AEL
1
Los Angeles, CA
$1,069
21
Bakersfield, CA
$31
2
Riverside, CA
$357
22
Tacoma, WA
$28
3
Oakland, CA
$349
23
Las Vegas, NV
$28
4
San Francisco, CA
$346
24
Anchorage, AK
$25
5
San Jose, CA
$243
25
Boston, MA
$23
6
Orange, CA
$214
26
Hilo, HI
$20
7
Seattle, WA
$128
27
Stockton, CA
$19
8
San Diego, CA
$128
28
Reno, NV
$18
9
Portland, OR
$98
29
Memphis, TN
$17
10
Ventura, CA
$89
30
Philadelphia, PA
$17
11
New York, NY
$56
31
San Luis Obispo, CA
$16
12
Vallejo, CA
$53
32
Salem, OR
$15
13
Santa Rosa, CA
$51
33
Fresno, CA
$14
14
Salt Lake City, UT
$40
34
Charleston, SC
$13
15
Sacramento, CA
$39
35
Albuquerque, NM
$13
16
St. Louis, MO
$34
36
Newark, NJ
$12
17
Eureka, CA
$34
37
Honolulu, HI
$12
18
Salinas, CA
$33
38
Atlanta, GA
$11
19
Santa Barbara, CA
$33
39
Modesto, CA
$11
20
Santa Cruz, CA
$33
40
Redding, CA
$10
Source: FEMA Publication 366, HAZUS 99 Estimated Annualized Earthquake Losses
for the United States (February 2001). Annualized earthquake losses (AEL) calculated
in 2000 dollars.
A single large earthquake can cause far more damage than the average annual
estimate. However, annualized estimates help provide comparisons of infrequent,
high impact events like damaging earthquakes, with more frequently occurring
CRS-8
hazards like floods, hurricanes, or other types of severe weather. The annualized
earthquake loss values shown in Table 4 represent future estimates, and are
calculated by multiplying losses from all potential future ground motions by their
respective frequencies of occurrence, and then summing these values.11
Estimating earthquake damage is not an exact science and depends on many
factors. Primarily, these are the probability of ground motion occurring in a
particular area (see Figure 1), and the consequences of that ground motion, which
are largely a function of building construction type and quality, and of the level of
ground motion and shaking during the actual event. Some researchers have
questioned whether the probability of ground motion estimates for regions of the
country that experience infrequent earthquakes, such as the New Madrid Seismic
Zone, are too high.12 These researchers question whether the benefits of building
structures to conform with the earthquake probability estimates merit the costs, in
light of the uncertainty in making those probability estimates.13 An uncertainty
analysis of the seismic hazard in the New Madrid Seismic Zone is beyond the scope
of this report.
The New Madrid Seismic Zone in the central United States is vulnerable to
large but infrequent earthquakes. A series of large (magnitude greater than 7.0)
earthquakes struck the Mississippi Valley over the winter of 1811-1812, centered
close to the town of New Madrid, MO. Some of the tremors were felt as far away as
Charleston, SC, and Washington, DC. The mechanism for the earthquakes in the
New Madrid zone is poorly understood,14 and no earthquakes of comparable
magnitude have occurred in the area since these events. Such factors contribute to
the difficulty of making a reasonable damage estimate for a low-frequency, high-
impact event in the region based on the probability of an earthquake of similar
magnitude occurring. This uncertainty has implications for policy decisions to
ameliorate risk, such as setting building codes, and for designing and building
structures to withstand a level of shaking commensurate with the risk. Developers
of building codes tend to err on the side of caution.
Table 4 also shows annualized earthquake losses for the cities of New York,
Boston, and Newark, where no destructive earthquakes have struck for generations.15
11 FEMA 366
12 Andrew Newman, Seth Stein, John Weber, Joseph Engeln, Ailin Mao, and Timothy
Dixon, “Slow Deformation and Lower Seismic Hazard in the New Madrid Seismic Zone,”
Science, v. 284 (April 23, 1999), pp. 619-621.
13 Seth Stein, Joseph Tomasello, and Andrew Newman, “Should Memphis Build for
California’s Earthquakes?”, Eos, v. 84, no. 19, (May 13, 2003), pp. 177, 184-185.
14 In contrast to California, where earthquakes occur on the active margin of the North
American tectonic plate, the New Madrid seismic zone is not on a plate boundary but may
be related to old faults in the interior of the plate, marking a zone of tectonic weakness.
15 The largest earthquakes in New York, New Jersey, and Massachusetts were, respectively,
1944 Massena, NY, magnitude 5.8, felt from Canada south to Maryland; 1783 New Jersey,
magnitude 5.3, felt from New Hampshire to Pennsylvania; 1755 Cape Ann and Boston, MA,
(continued...)
CRS-9
Those cities represent areas of relatively low seismic hazard, but have high
populations and dense infrastructure, which produces a significant risk to people and
structures, according to some estimates.16 In the absence of any significant or
damaging earthquakes for those cities in recent memory, however, the actual risk is
difficult to grasp intuitively.
Monitoring
Congress authorized the USGS to monitor seismic activity in the United States
in the 1990 reauthorization of the National Earthquake Hazards Reduction Act (P.L.
101-614). The USGS operates a nationwide network of seismographic stations called
the Advanced National Seismic System (ANSS), which includes the National Strong-
Motion Project (NSMP). Globally, the USGS and the Incorporated Research
Institutions for Seismology (IRIS) operate 140 seismic stations of the Global Seismic
Network (GSN) in more than 80 countries. The GSN provides worldwide coverage
of earthquakes, including reporting and research, and also monitors nuclear
explosions.
Advanced National Seismic System (ANSS). “The mission of ANSS is
to provide accurate and timely data and information products for seismic events,
including their effects on buildings and structures, employing modern monitoring
methods and technologies.”17 If fully implemented, ANSS would encompass more
than 7,000 earthquake sensor systems covering parts of the nation vulnerable to
earthquake hazards. Currently, the system includes 696 stations consisting of
backbone stations, dense urban networks, and regional networks.18 Approximately
6,000 of the planned stations are to be installed in 26 high-risk urban areas to monitor
strong ground shaking and how buildings and other structures respond. Currently,
five high-risk urban areas have instruments deployed in sufficient density to generate
the data to produce near real-time maps, called ShakeMaps,19 which can be used in
emergency response during and after an earthquake.
Approximately 1,000 new instruments are to replace aging and obsolete stations
in the networks that now monitor the nation’s most seismically active regions. The
current regional networks contain a mix of modern, digital, broadband, and high-
resolution instruments that can provide real-time data; they are supplemented by
older instruments that may require manual downloading of data. Universities in the
region typically operate the regional networks and will likely continue to do so as
ANSS is implemented.
15 (...continued)
intensity of VIII on the Modified Mercalli Scale, felt from Nova Scotia to Chesapeake Bay
(USGS Earthquake Hazards Program).
16 FEMA 366 and USGS Circular 1188, Table 3.
17 USGS Earthquake Hazards Program, at [http://earthquake.usgs.gov/research/monitoring/
anss/].
18 William Leith, USGS, telephone conversation Oct. 30, 2006.
19 ShakeMap is a product of the USGS Earthquake Hazards Program in conjunction with
regional seismic network operators; see Shakemap below.
CRS-10
Lastly, approximately 100 instruments comprise the existing “backbone” of
ANSS, with a roughly uniform distribution across the United States, including
Alaska and Hawaii. These instruments provide a broad and uniform minimum
threshold of coverage across the country. The backbone network consists of USGS-
deployed instruments and other instruments that serve both ANSS and the
EarthScope project (described below, under “Research — Understanding
Earthquakes”).
In 2004, Congress passed the National Earthquake Hazards Reduction Program
Reauthorization Act of 2004 (P.L. 108-360), which authorized $30 million for ANSS
in FY2005 and $36 million per year through FY2009. Congress first authorized the
program with P.L. 106-503 at a level of $38 million for FY2002 and $44 million
FY2003. Total expenditures for ANSS from FY2002 to FY2006 are slightly more
than $28 million, or approximately 15% of authorized levels. Overall, ANSS is
about 10% complete.
National Strong-Motion Project (NSMP). Under ANSS, the USGS
operates the NSMP to record seismic data from damaging earthquakes in the United
States on the ground and in buildings and other structures in densely urbanized areas.
The program currently has 900 strong-motion20 instruments in 701 permanent
stations across the United States and in the Caribbean. The NSMP has three
components: data acquisition, data management, and research. The near real-time
measurements collected by the NSMP are used by other government agencies for
emergency response and real-time warnings. If fully implemented, the ANSS
program would deploy about 3,000 strong-motion instruments, and the NSMP
program would operate those strong-motion instruments located in buildings and
other structures. Many of the current NSMP instruments are older designs and are
being upgraded with modern seismometers.
Global Seismic Network (GSN). The GSN is a system of broadband digital
seismographs arrayed around the globe and designed to collect high-quality data that
are readily accessible to users worldwide, typically via computer. Currently, 140
stations have been installed in 80 countries and the system is nearly complete,
although in some regions the spacing and location of stations has not fully met the
original goal of uniform spacing of approximately 2,000 kilometers. The system is
currently providing data to the United States and other countries and institutions for
earthquake reporting and research, and for monitoring nuclear explosions to assess
compliance with the Comprehensive Test Ban Treaty. The Emergency Supplemental
Appropriations Act for Defense, the Global War on Terror, and Tsunami Relief, 2005
(P.L. 109-13) provided more than $8 million to the USGS, of which $1.45 million
was to expand the GSN real-time communications.21 Funding for the GSN totaled
$7.3 million in FY2007.22
20 Strong motion seismometers, or accelerometers, are special sensors that measure the
acceleration of the ground during large (>6.0 magnitude) earthquakes.
21 See also CRS Report RL32739, Tsunamis: Monitoring, Detection, and Early Warning
Systems, by Wayne A. Morrissey.
22 William Leith, USGS, personal communication, Apr. 2, 2007.
CRS-11
The Incorporated Research Institutions for Seismology (IRIS)23 coordinates the
GSN and manages and makes available the large amounts of data that are generated
from the network. The actual network of seismographs is organized into two main
components, each managed separately. The USGS operates two-thirds of the stations
from its Albuquerque Seismological Laboratory, and the University of California-San
Diego manages the other third via its Project IDA (International Deployment of
Accelerometers). Other universities and affiliated agencies and institutions operate
a small number of additional stations. IRIS, with funding from the NSF, supports all
of the stations not funded through the USGS appropriations.
Detection, Notification, and Warning
Unlike other natural hazards, such as hurricanes, where predicting the location
and timing of landfall is becoming increasingly accurate, the scientific understanding
of earthquakes does not yet allow for precise earthquake prediction. Instead,
notification and warning typically involves communicating the location and
magnitude of an earthquake as soon as possible after the event to emergency response
providers and others who need the information.
Some probabilistic earthquake forecasts are being made available now that give,
for example, a 24-hour probability of earthquake aftershocks for a particular region,
such as California. These forecasts are not predictions, and are currently intended to
increase public awareness of the seismic hazard, improve emergency response, and
increase scientific understanding of the short-term hazard.24 In the California
example, a time-dependent map is created and updated every hour by a system that
considers all earthquakes, large and small, detected by the California Integrated
Seismic Network,25 and calculates a probability that each earthquake will be followed
by an aftershock26 that can cause strong shaking. The probabilities are calculated
from known behavior of aftershocks and the possible shaking pattern based on
historical data.
When a destructive earthquake occurs in the United States or in other countries,
the first reports of its location, or epicenter,27 and magnitude originate either from the
National Earthquake Information Center in Golden, CO, or from one of the regional
23 IRIS is a university research consortium, primarily funded by NSF, that collects and
distributes seismographic data.
24 USGS Open-File Report 2004-1390, and California 24-hour Aftershock Forecast Map,
at [http://pasadena.wr.usgs.gov/step/].
25 The California Integrated Seismic Network is the California region of ANSS; see
[http://www.cisn.org/].
26 Earthquakes typically occur in clusters, in which the earthquake with the largest
magnitude is called the main shock, events before the main shock are called foreshocks, and
those after are called aftershocks. See also [http://pasadena.wr.usgs.gov/step/aftershocks.
html].
27 The epicenter of an earthquake is the point on the earth’s surface directly above the
hypocenter. The hypocenter is the location beneath the earth’s surface where the fault
rupture begins.
CRS-12
seismic networks that are part of ANSS. Other organizations, such as universities,
consortia, and individual seismologists may also contribute information about the
earthquake after the event. Products, such as ShakeMap, are assembled as rapidly as
possible to assist in emergency response and damage estimation following a
destructive earthquake.
National Earthquake Information Center (NEIC). The NEIC, part of the
USGS, is located in Golden, CO. Originally established as part of the National
Ocean Survey (Department of Commerce) in 1966, the NEIC was made part of the
USGS in 1973. With data gathered from the networks described above and from
other sources, the NEIC determines the location and size of all destructive
earthquakes that occur worldwide and disseminates the information to the appropriate
national or international agencies, government public information channels, news
media, scientists and scientific groups, and the general public.
The NEIC has long-standing agreements with key emergency response groups,
federal, state, and local authorities, and other key organizations in earthquake-prone
regions who receive automated alerts — typically location and magnitude of an
earthquake — within a few minutes of an event in the United States. The NEIC
sends these preliminary alerts by email and pager immediately after an earthquake’s
magnitude and epicenter are automatically determined by computer.28 This initial
determination is then checked by around-the-clock staff who confirm and update the
magnitude and location data.29 After the confirmation, a second set of notifications
and confirmations are triggered to key recipients by email, pager, fax, and telephone.
For earthquakes outside the United States, the NEIC notifies the State
Department Operations Center, and often sends alerts directly to staff at American
embassies and consulates in the affected countries, to the International Red Cross, the
U.N. Department of Humanitarian Affairs, and other recipients who have made
arrangements to receive alerts.
With the advent of the USGS Earthquake Notification Service (ENS),
notifications of earthquakes detected by the ANSS/NEIC are provided free to
interested parties. Users of the service can specify the regions of interest, establish
notification thresholds of earthquake magnitude, designate whether they wish to
receive notification of aftershocks, and even set different magnitude thresholds for
daytime or nighttime to trigger a notification.
ShakeMap. Traditionally, the information commonly available following a
destructive earthquake has been epicenter and magnitude, as in the data provided by
the NEIC described above. Those two parameters by themselves, however, do not
always indicate the intensity of shaking and extent of damage following a major
earthquake. Recently, the USGS developed a product called ShakeMap that provides
a near real-time map of ground motion and shaking intensity following an earthquake
28 Stuart Simkin, NEIC, Golden, CO, telephone conversation, Nov. 4, 2006.
29 In early 2006, the NEIC implemented an around-the-clock operation center and seismic
event processing center in response to the Indonesian earthquake and resulting tsunami of
December 2004. Funding to implement 24/7 operations was provided by P.L. 109-13.
CRS-13
in areas of the United States where the ShakeMap system is in place. Currently,
ShakeMaps are available for northern California, southern California, the Pacific
Northwest, Nevada, Utah, and Alaska.30 Figure 3 shows an example of a ShakeMap.
Figure 3. Example of a ShakeMap
Source: USGS, [http://earthquake.usgs.gov/eqcenter/shakemap/nc/shake/40206647/].
Note: Earthquake occurred northeast of the The Geysers, CA, on December 1, 2007, at
12:50 p.m., with a magnitude of 3.9. Viewed on January 12, 2008.
With improvements to the regional seismographic networks in the areas where
ShakeMap is available, new real-time telemetry from the region, and advances in
digital communication and computation, ShakeMaps are now triggered automatically
and made available within minutes of the event via the Web. In addition, better maps
are now available because of recent improvements in understanding the relationship
between the ground motions recorded during the earthquake and the intensity of
resulting damage. The maps produced portray the extent of damaging shaking and
can be used by emergency response and for estimating loss following a major
earthquake. If databases containing inventories of buildings and lifelines31 are
available, they can be combined with shaking intensity data to produce maps of
estimated damage.
30 See [http://earthquake.usgs.gov/eqcenter/shakemap/].
31 Lifelines are essential utility and transportation systems.
CRS-14
The ShakeMaps have limitations, especially during the first few minutes
following an earthquake before more data arrive from distributed sources. Because
they are generated automatically, the initial maps are preliminary, and may not have
been checked by human oversight when first made available. They are considered
a work in progress, but are deemed to be very promising, especially as more modern
seismic instruments are added to the regional networks under ANSS and the
computational and telecommunication ability improves.
National Earthquake Hazards Reduction Program (NEHRP)
In 1977 Congress passed the Earthquake Hazards Reduction Act (P.L. 95-124)
establishing NEHRP as a long-term earthquake risk reduction program for the United
States. The program initially focused on research, led by USGS and NSF, toward
understanding and ultimately predicting earthquakes. Earthquake prediction has
proved intractable thus far, and the NEHRP program shifted its focus to minimizing
losses from earthquakes after they occur. FEMA was created in 1979 and President
Carter designated it as the lead agency for NEHRP. In 1980, Congress reauthorized
the Earthquake Hazards Reduction Act (P.L. 96-472), defining FEMA as the lead
agency and authorizing additional funding for earthquake hazard preparedness and
mitigation to FEMA and the National Bureau of Standards (now NIST).
Mitigation. In 1990, Congress reauthorized NEHRP (P.L. 101-614) and made
substantive changes, to decrease the emphasis on earthquake prediction, clarify the
role of FEMA, clarify and expand the program objectives, and require federal
agencies to adopt seismic safety standards for new and existing federal buildings. In
2004, Congress reauthorized NEHRP through FY2009 (P.L. 108-360) and shifted
primary responsibility for planning and coordinating NEHRP from FEMA to NIST.
It also established a new interagency coordinating committee and a new advisory
committee, both focused on earthquake hazards reduction.
The current program activities are focused on four broad areas:
! developing effective measures to reduce earthquake hazards;
! promoting the adoption of earthquake hazards reduction measures
by federal, state, and local governments, national building standards
and model building code organizations, engineers, architects,
building owners, and others who play a role in planning and
constructing buildings, bridges, structures, and critical infrastructure
or lifelines;
! improving the basic understanding of earthquakes and their effects
on people and infrastructure, through interdisciplinary research
involving engineering, natural sciences, and social, economic, and
decision sciences; and
! developing and maintaining ANSS, the George E. Brown Jr.
Network for Earthquake Engineering Simulation (NEES),32 and the
GSN.
32 NEES is an NSF-funded project that consists of 15 experimental facilities and an IT
infrastructure with a goal of mitigating earthquake damage by the use of improved materials,
designs, construction techniques, and monitoring tools.
CRS-15
The House Science Committee report on H.R. 2608 (P.L. 108-360) noted that
NEHRP has produced a wealth of useful information since 1977, but it also stated
that the program’s potential has been limited by the inability of the NEHRP agencies
to coordinate their efforts.33 The committee felt that restructuring the program with
NIST as the lead agency, directing funding towards appropriate priorities, and
implementing it as a true interagency program would lead to improvement.
Under the reauthorization, the Director of NIST chairs the Interagency
Coordinating Committee, which is composed of the directors of FEMA, USGS, NSF,
the Office of Science and Technology Policy, and the Office of Management and
Budget. The Interagency Coordinating Committee is charged with overseeing the
planning, management, and coordination of the program. Primary responsibilities for
the NEHRP agencies break down as follows:
! NIST supports the development of performance-based seismic
engineering tools and works with other groups to promote the
commercial application of the tools through building codes,
standards, and construction practices.
! FEMA assists other agencies and private-sector groups to prepare
and disseminate building codes and practices for structures and
lifelines, and aid development of performance-based codes for
buildings and other structures.
! USGS conducts research and other activities to characterize and
assess earthquake risks, and (1) operates a forum, using the NEIC,
for the international exchange of earthquake information; (2) works
with other NEHRP agencies to coordinate activities with earthquake
reduction efforts in other countries; and (3) maintains seismic hazard
maps in support of building codes for structures and lifelines, and
other maps needed for performance-based design approaches.
! NSF supports research to improve safety and performance of
buildings, structures, and lifelines using the large-scale experimental
and computational facilities of NEES and other institutions engaged
in research and implementation of NEHRP.
Table 5 shows authorization of appropriations for NEHRP from FY2005
through FY2008 and the enacted amounts by agency through FY2007. The total
enacted amount for FY2005-FY2007 is $366.8 million, $157.2 million less than the
amount authorized in P.L. 108-360 of $524 million over the three-year span. Slightly
less than $200 million is authorized under the law for FY2009.
33 U.S. House, Committee on Science, National Earthquake Hazards Reduction Program
Reauthorization Act of 2003, H.Rept. 108-246 (Aug. 14, 2003), p. 13.
CRS-16
Table 5. Authorized and Enacted Funding for NEHRP
($ millions)
Agency
FY05
FY05
FY06
FY06
FY07
FY07
FY08
FY08
Auth.
Enact.
Auth.
Enact.
Auth.
Enact.
Auth.
Request
NIST
10.0
0.9
11.0
0.9
12.1
1.7
13.3
6.4
FEMA
21.0
14.7
21.6
9.5
22.3
9.1
23.0
9.1
USGS
77.0
58.4
84.4
54.5
85.9
55.4
87.4
56.5
NSF
58.0
53.1
59.5
53.8
61.2
54.8
62.9
55.7
Total
166.0
127.1
176.5
118.7
181.5
121.0
186.6
127.7
Source: NEHRP program office, at [http://www.nehrp.gov/plans/index.htm].
HAZUS-MH. FEMA, under contract with the National Institute of Building
Sciences,34 developed a methodology and software program called the Hazards U.S.
Multi-Hazard (HAZUS-MH).35 The program allows a user to estimate losses from
damaging earthquakes, hurricane winds, and floods before a disaster occurs. The
pre-disaster estimates could provide a basis for developing mitigation plans and
policies, preparing for emergencies, and planning response and recovery. HAZUS-
MH combines existing scientific knowledge about earthquakes (for example,
ShakeMaps, described above), engineering information that includes data on how
structures respond to shaking, and geographic information system (GIS) software to
produce maps and display hazards data including economic loss estimates. The loss
estimates produced by HAZUS-MH include the following:
! physical damage to residential and commercial buildings, schools,
critical facilities, and infrastructure;
! economic loss, including lost jobs, business interruptions, repair and
reconstruction costs; and
! social impacts, including estimates of shelter requirements,
displaced households, and number of people exposed to the disaster.
In addition to furnishing information as part of earthquake mitigation efforts,
HAZUS-MH can also be used to support real-time emergency response activities by
state and federal agencies after a disaster. Twenty-seven HAZUS-MH user groups36
— cooperative ventures among private, public, and academic organizations that use
34 The National Institute of Building Sciences (NIBS) is a non-profit non-governmental
organization established by Congress in the Housing and Community Development Act of
1974 (PL 99-383). NIBS is funded through dues from its membership, private sector
contributions, and contracts with federal and state agencies. The mission of NIBS is to
improve the building regulatory environment, facilitate introducing new products and
technologies into the building process, and disseminate technical and regulatory
information. See [http://www.nibs.org/].
35 See [http://www.fema.gov/plan/prevent/hazus/].
36 See [http://www.hazus.org/].
CRS-17
the HAZUS-MH software — have formed across the United States to help foster
better-informed risk management for earthquakes and other natural hazards.
HAZUS-MH software was first released to the public in 1997 and the first user
group, the Bay Area HAZUS-MH User Group, was formed the same year.
Research — Understanding Earthquakes
U.S. Geological Survey. Under NEHRP, the USGS has responsibility for
conducting targeted research into improving the basic scientific understanding of
earthquake processes. The current earthquake research program at the USGS covers
six broad categories:37
! Borehole geophysics and rock mechanics: studies to understand heat
flow, stress, fluid pressure, and the mechanical behavior of fault-
zone materials at seismogenic38 depths to yield improved models of
the earthquake cycle.
! Crustal deformation: studies of the distortion or deformation of the
earth’s surface near active faults as a result of the motion of tectonic
plates.
! Earthquake geology and paleoseismology: studies of the history,
effects, and mechanics of earthquakes.
! Earthquake hazards: studies of where, why, when, and how
earthquakes occur.
! Regional and whole-earth structure: studies using seismic waves
from earthquakes and man-made sources to determine the structure
of the planet ranging from the local scale, to the whole crust, mantle,
and even the earth’s core.
! Strong-motion seismology, site response, and ground motion:
studies of large-amplitude ground motions and the response of
engineered structures to those motions using accelerometers.
National Science Foundation. NSF supports fundamental research into
understanding the earth’s dynamic crust. Through its Earth Sciences Division39 (part
of the Geosciences Directorate), NSF distributes research grants and coordinates
programs investigating the crustal processes that lead to earthquakes around the
globe. Recently, NSF initiated a Major Research Equipment and Facilities
Construction (MREFC) project called EarthScope.40 EarthScope is deploying
instruments across the United States to study the structure and evolution of the North
American Continent, and to investigate the physical processes that cause earthquakes
and volcanic eruptions. EarthScope, a five-year, $200 million project, began in 2003,
is funded by NSF, and is conducted in partnership with the USGS and NASA.
37 See [http://earthquake.usgs.gov/research/].
38 Seismogenic means capable of generating earthquakes.
39 See [http://www.nsf.gov/div/index.jsp?div=EAR].
40 See [http://www.earthscope.org/].
CRS-18
EarthScope instruments will form a framework for broad, integrated studies of
the four-dimensional (three spatial dimensions, plus time) structure of North
America. The project is divided into three main programs:
! The San Andreas Fault Observatory at Depth (SAFOD): a deep
borehole observatory drilled through the San Andreas fault zone
close to the hypocenter of the 1966 Parkfield, CA, magnitude 6
earthquake.
! The Plate Boundary Observatory (PBO): a system of GPS arrays and
strainmeters41 that measure the active boundary zone between the
Pacific and North American tectonic plates in the western United
States.
! USArray: four hundred transportable seismometers that will be
deployed systematically across the United States on a uniform grid
to provide a complete image of North America from continuous
seismic measurements.
Through its Engineering Directorate, NSF funds NEES,42 a project intended to
operate until 2014, aimed at understanding the effects of earthquakes on structures
and materials. To achieve the program’s goal, the facilities conduct experiments and
computer simulations of how buildings, bridges, utilities, coastal regions, and
materials behave during an earthquake. Table 6 (above) shows authorization levels
for NEES through 2009.
Conclusions
The 2003 reauthorization of NEHRP shifted leadership of the multiagency
program from FEMA to NIST and authorized the program through FY2009.
Congress may wish to determine whether the reorganized structure has yielded
expected benefits for the program, now in its fourth year since P.L. 108-360 was
enacted. Appropriations for NEHRP have not met levels authorized in the law for
FY2005 through FY2007, falling short by almost 24% in FY2005 and 33% in
FY2007. What effect funding at the levels enacted through FY2007 has had on all
programs authorized under NEHRP is unclear, although progress in some programs
has been slower than anticipated. For example, the Advanced National Seismic
System (ANSS), an integrated system of earthquake sensors deployed across the
country, is about 10% complete, in part because appropriated funds for ANSS have
historically been a fraction of the authorized levels. To what extent the current rate
41 A strainmeter is a tool used by seismologists to measure the motion of one point relative
to another.
42 A non-profit NEES consortium (NEESinc.) has operated the facilities for the 10-year
operating lifespan at the following institutions: Cornell University; Lehigh University;
Oregon State University; Rensselaer Polytechnical Institute; University of Buffalo-State
University of New York; University of California-Berkeley; University of California-Davis;
University of California-Los Angeles; University of California-San Diego; University of
California-Santa Barbara; University of Colorado-Boulder; University of Illinois at Urbana-
Champaign; University of Minnesota; University of Nevada-Reno; University of Texas at
Austin. See [http://www.nees.org/].
CRS-19
of progress toward meeting the goals of ANSS affects the U.S. capability to detect
earthquakes and minimize losses after an earthquake occurs is not clear.
Congress may also wish to examine if and how new research results —
generated under EarthScope, a research program at NSF distinct from NEHRP — on
understanding earthquakes are contributing to the nation’s resilience to earthquake
disasters. An ongoing question is how scientific advances in understanding the
fundamental nature of earthquakes — funded by EarthScope and other programs at
NSF and the USGS — can be applied towards improving the U.S. capability to
minimize losses from destructive earthquakes.
Additional Reading
Aspects of the federal role in the aftermath of a damaging earthquake or other
natural catastrophes — the response and recovery phase — are covered in the
following CRS reports.
CRS Report RL33330, Community Development Block Grant Funds in Disaster
Relief and Recovery, by Eugene Boyd.
CRS Report RL33060, Tax Deductions for Catastrophic Risk Insurance Reserves:
Explanation and Economic Risk Analysis, by David L. Brumbaugh and Rawle
O. King.
CRS Report RL31734, Federal Disaster Recovery Programs: Brief Summaries, by
Mary B. Jordan.
CRS Report RL32847, Tsunamis and Earthquakes: Is Federal Disaster Insurance
in Our Future?, by Rawle O. King.
CRS Report RS22268, Repairing and Reconstructing Disaster-Damaged Roads and
Bridges: The Role of Federal-Aid Highway Assistance, by Robert S. Kirk.
CRS Report RS22273, Emergency Contracting Authorities, by John R. Luckey.
CRS Report RL34146, FEMA’s Disaster Declaration Process: A Primer, by Francis
X. McCarthy.
CRS Report RL33206, Vulnerability of Concentrated Critical Infrastructure:
Background and Policy Options, by Paul W. Parfomak.
In response to conference report H.Rept. 109-699, accompanying the FY2007
Department of Homeland Security Appropriations Act (P.L. 109-295), FEMA
released the following report to Congress:
Federal Emergency Management Agency, “Federal Earthquake Response Plans:
Report to Congress,” December 2007, 92 pages.