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REDucº EarTºuake losses Throughout The united states
The USGS Earthquake Hazards Program in NEHRP–
Investing in a Safer Future
In 1977. Congress authorized the
Hazard
creation of the National Earth- Higest -
quake Hazards Reduction Program --
(NEHRP) to improve the Nation's º,
understanding of earthquake haz- * * Lowest
Q Magnitude 6.5 and greater
ards and to mitigate their effects. quakes since 1978
Earthquakes are the most costly
natural hazard faced by the United
States. Twenty-five years of work by
the U.S. Geological Survey (USGS),
in close cooperation with the three
other NEHRPagencies, has yielded -->
major advances in earthquake pre-
paredness and monitoring, as well
as a vastly improved understanding
of earthquake hazards, processes,
and effects. The USGS is poised to
build on these accomplishments,
helping through WEHRP to protect
lives and property in the future
earthquakes that are certain to
strike the United States.
-
As shown by this U.S. Geological Survey (USGS) national seismic-hazard map, earthquake hazards
exist throughout the United States. USGS national and regional seismic-hazard maps forecast the
amount of shaking expected over specified time periods. Many parts of the Central and Eastern
United States have moderate to high long-term hazard, even though they have not experienced recent
large quakes. Successive updates of USGS seismic-hazard maps are used to revise building codes
and are also widely used by structural engineers and government agencies. The next generation of
such maps will provide time-dependent probabilities that take into account the effects of prior quake
The U.S. Geological Survey (USGS) Earthquake Hazards Program moni-
tors the Nation's earthquakes, studies why they occur and how they shake the
ground, provides quantitative earthquake-hazard assessments, helps promote
loss-reduction measures using these results, and provides crucial scientific
information to assist emergency responders when earthquakes occur. The USGS
Earthquake Hazards Program operates under the National Earthquake Hazards
Reduction Program (NEHRP), created by Congress in 1977. To meet the chal-
lenges and potential of NEHRP activities supported by the USGS Earthquake
Hazards Program are managed under four broad interrelated objectives:
• Improve quantification of seismic hazards—The USGS produces quanti-
tative hazard-assessment products that enable the public and private sectors
to assess earthquake hazards and implement effective mitigation strategies.
• Complete the modernization and expansion of real-time earth-
quake notification and monitoring systems—The USGS is tasked
with collecting, interpreting, and disseminating information on the
earthquakes that occur throughout the United States and on significant
quakes worldwide in support of disaster response, earthquake prepared-
ness, national Security, Scientific research, and public hazard awareness.
• Achieve better scientific understanding of earthquake processes and
effects—The USGS pursues research on earthquake occurrence and
U.S. Department of the Interior
U.S. Geological Survey
occurrence on future earthquake likelihood.
effects for the purpose of developing and improving hazard-assessment
methods and loss-reduction strategies.
• Provide national and local leadership to engage communities in
earthquake safety practices—The USGS works with user communi-
ties to ensure that its products are readily available, easily understood,
and appropriately used for earthquake mitigation and response.
The work of the USGS Earthquake Hazards Program focuses both on
the Nation as a whole and also on particular regional needs and problems
in areas where quake risk is the greatest. The program’s work of the is
carried out by USGS scientific and technical personnel and also through
a system of competitive external grants and contracts that is allotted
one-quarter of program funds. In the past 25 years, this grants program
has funded approximately 2,500 grants and cooperative agreements with
state geological surveys, university researchers and research consortia,
state and local government agencies, and nonprofit and other organi-
zations in the private sector. USGS also works closely with the other
NEHRP agencies (FEMA, NSF, and the National Institute of Standards
HNEHRP agencies, such as NASA,
* ,
and Technology) and thſ
NOAA, and USAID." * .
COLLECTION-
USGS Fact Sheet 017-03
2003









U.S. Geological Survey (USGS) rock-mechanics laboratories have been the
birthplace of a stream of breakthroughs on the nature of rock friction and
its control of earthquakes—their size, rate, interactions, and the ground
shaking they produce. These studies, in combination with extensive field
tests, have led to new theories about the physics of faulting and the role of
fluids in quake generation. USGS is now poised to directly test these theo-
ries not just on laboratory scale models (left) but also at a depth of 2.5 miles
in the San Andreas Fault (right) at Parkfield, California. There, the San An-
dreas Fault Observatory at Depth (SAFOD) is being built in partnership with
the National Science Foundation (NSF) as part of the EarthScope program.
The 1.3-mile-deep SAFOD pilot hole was successfully completed in 2002.
Accomplishments and Impacts of the USGS Earthquake
Hazards Program
Over the past 25 years, NEHRP has made the Nation safer from the rav-
ages of earthquakes. One of the flagship products from NEHRP contributing
to this achievement are the national seismic-hazard maps that the USGS has
produced since 1976. These maps are derived by estimating the likelihood
of future earthquakes along active faults throughout different regions and
evaluating the ground shaking that these quakes would cause. These seismic-
hazard maps are the Scientific basis of Seismic provisions in building codes
enacted throughout the United States to prevent loss of life and limit damage
during large earthquakes. The 1996 national seismic-hazard maps are directly
included in design maps in the NEHRP Recommended Provisions, published
by the Building Seismic Safety Council and the Federal Emergency Manage-
ment Agency (FEMA). Seismic provisions in both the 2000 International
Building Code (the merging of the three major national model codes) and
the International Residential Code are also derived from these maps. These
codes have now been adopted by jurisdictions in 37 states. Thus, the USGS-
produced national seismic-hazard maps are now being used to make billions of
dollars of new construction each year safer from earthquakes.
The national seismic-hazard maps are also used in FEMA's retrofit guide-
lines, ensuring that older buildings are strengthened so that they withstand
future earthquakes. In addition, these maps and associated products are used
in the design of highway bridges, landfills under EPA regulation, and dams,
as well as in the setting of earthquake-insurance premiums and the cost of
reinsurance. The California Earthquake Authority uses seismic-hazard maps
produced jointly by the USGS and the California Geological Survey to set
earthquake premiums for the State's quake-insurance program. Pension
funds apply these maps to evaluate the risks to their portfolios of properties.
Presidential executive orders specify that new and leased Federal buildings
must adhere to the NEHRP Recommended Provisions. The State of Oregon
recently raised seismic requirements in construction along the southern
part of its coast, largely on the basis of information presented in the USGS
Seismic-hazard maps.
The advances in earthquake-hazard assessments during the first 25
years of NEHRP have their roots in pioneering USGS field, laboratory, and
theoretical research focused on understanding the basic physical processes
associated with earthquakes. Key breakthroughs include:
• Improved quantification of regional seismic-energy attenuation with
distance from an earthquake.
• Use of Global Positioning System (GPS) stations to determine the rate
at which faults are being “loaded” (stressed) by the movements of the
tectonic plates that make up the Earth's outer shell.
• Discovery and documentation of large prehistoric earthquakes
through a new field of study known as paleoseismology (identifying
evidence of past quakes in trenches dug across faults, in riverbanks,
and from drowned coastlines).
• Use of new remote-sensing technology, such as LIDAR (light detection
and ranging), to identify active faults in heavily forested regions like the
Pacific Northwest.
• Quantification of the effects of soils and near-surface conditions in
amplifying strong ground motion.
• Advances in earthquake forecasting through improved understanding of
the physics of the fracture and friction of rocks in fault zones.
EARTHOUAKE DETECTIVE WORK REVEALS PREVIOUSLY UNKNOWN HAZARDS
USGS SHAKING-HAZARD MAPS
In the 1980s, U.S. Geological Survey (USGS) scientists discovered the
first evidence that very large earthquakes have repeatedly struck the Pa- 1976 1996
cific Northwest in the past Geologic and tree-ring studies showed that -
a strong earthquake of unknown magnitude struck the region in about
1700 a century before the Lewis and Clark expedition. Trees (left) died
when coastal areas were lowered during the quake, submerging their
roots in saltwater. In the 1990s, clues to this quake's magnitude were
found by USGS and Japanese researchers in 300-year-old administrative
records from Japan (lower left). Those records describe the effects of a
destructive tsunami (seismic sea wave) that occurred without the usual
warning of a nearby earthquake. The scientistspieced these and other
clues together and determined that only an extraordinarily powerful
earthquake from across the Pacific Ocean could have generated this
tsunami. They concluded that a quake of magnitude 9 struck the Pacific
N \
º
eºs --tº Northwest on the evening of January 26, 1700 releasing 30 times as
º .** much energy as the largest quake ever recorded in California.
- - When this potential for magnitude 9 earthquakes offshore Washington Increasing hazard—-
--- --~~ and Oregon was recognized USGS and the Federal Emergency
- Tºsº. Management Agency (FEMA) helped to form the Cascadia Region Earthquake Workgroup (CREW), which has involved Federal
- - and local government officials with business and industrial interests to jointly and effectively address earthquake hazards and
- _+* promote mitigation in the Pacific Northwest USGS earthquake-hazard maps (right) that are used to set building codes were
- also revised to reflect the recently identified hazard in the Pacific Northwest
(Courtesy of Morioka Chūd Kóminkan.)





"SHAKEMAP"—ANEW TECHNOLOGYT0 ADEMERGENCY RESPONSE
PNSN Rapid Instrumental Intensity Map Epicenter: 17.0 km NE of Olympia, WA
M 6.7 N47.15 W122.73
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0 º 45 MILES’.
|-
46.5°º || || º ºº:
#45 kilometersº
Increasing intensity of shaking —-
This U.S. Geological Survey (USGS) "ShakeMap" shows shaking intensities during
the 2001 magnitude 6.7 Nisqually, Washington, earthquake, which caused $2 billion
in damage and economic losses in the Olympia-Seattle area. The capability to
automatically generate computer maps of the intensity of ground shaking and to
provide them to the public on the Internet within minutes of a quake was devel-
oped after the 1994 Northridge, California, earthquake. ShakeMaps help greatly
in the quick assessment of the scope of an earthquake emergency and in guiding
emergency response. ShakeMap requires data from modern seismic networks
with digital strong-motion recording capabilities and real-time telecommunications
feeds. Currently few urban areas in the United States possess such networks.
For this reason, ShakeMap is currently available only in the Los Angeles, San
Francisco, Seattle, and Salt Lake City areas. Full implementation by the USGS of
the Advanced National Seismic System (ANSS) will allow expansion of ShakeMap
to all large U.S. metropolitan areas with moderate to high seismic risk.
The USGS Earthquake Hazards Program has also realized major
improvements in its ability to provide timely and informative earthquake
reports and information. To fulfill its Federal responsibility to monitor
seismic activity in the United States, USGS operates the U.S. National
INSTRUMENTED BUILDINGS PROVIDE CRUCIAL DATA
To design safer buildings and to provide vital information for strengthening
older ones, U.S. Geological Survey earthquake engineers have installed
arrays of seismic instruments in several buildings, such as San Francisco's
Transamerica tower (right), in order to capture their motion during earth-
quakes. The resulting records reveal how structural systems perform in
quakes and how shaking is amplified on upper floors, as demonstrated
here by records from the tower during the 1989 Loma Prieta earthquake.
In that quake, 63 people were killed when other structures collapsed. A
major objective of the Advanced National Seismic System (AWSS) is to
instrument many representative building types and key structures across
the country to acquire the data that engineers need to help prevent loss of
life in future quakes.
DISCOVERING HDDEN FAULTS
Discovering active faults in
thickly vegetated regions, such -
as the Puget Sound area of - º:
Washington (photo) is very " Fault
challenging because their -
topographic expressions are
hard to see. However, a new
airborne laser technology,
called LIDAR (light detection
and ranging) is fast changing
this. LIDAR imaging can see
through forests to permit high-
resolution measurement of
topography to a precision of a
foot or less, showing otherwise
invisible faults. Using LIDAR,
the U.S. Geological Survey has
been able to identify previously
unknown faults in the Seattle
and Puget Sound area. The
LIDAR image at right reveals
the Toe Jam Hill Fault, marked
by a conspicuous east-west
topographic trend (arrows).
In addition, the image shows
north-south grooves in the
Earth's surface that were
formed by the movement of
ancient glaciers.
1 KILOMETER
(Courtesy of Kitsap County Public Utility District)
Seismograph Network, the National Earthquake Information Center, and
the National Strong Motion Program and supports 14 regional seismic
networks in areas of moderate to high quake activity. Additionally, the
USGS, in cooperation with the National Science Foundation (NSF),
operates the Global Seismic Network, which provides the main source of
worldwide earthquake information.
USGS has capitalized on the revolution in information technology to
achieve dramatic advances in real-time seismic-data analysis and rapid
earthquake notification. The most noteworthy result of this is “ShakeMap,”
a system for automatically generating, within minutes of an earthquake,
maps of areas subjected to strong shaking. ShakeMap, where available, can
be delivered in 10 minutes or less and thus forms the basis for emergency
response by cities, states, Federal agencies, and lifeline operators.
Complementing ShakeMap are a suite of other real-time earthquake
products, such as earthquake paging and e-mail services, real-time earth-
quake location maps, automatic Web pages with information on signifi-
cant events, and aftershock probability estimators. Additionally, USGS




HELPING THE PUBLIC PREPARE FOR EARTHOUAKES
º - - -
- º º |
-
-
-Es
5. To sº. amplification
9% C. -
= . The U.S. Geological Survey (USGS) and
Putting Down Roots the Southern California Earthquake
in Earthquake Country Center (SCEC) work jointly to produce
an array of earthquake-hazard products
for southern California. The map above
shows how the level of shaking is likely
to vary across the Los Angeles Basin
because of soft sediments and subsur-
face geologic structures. In the wake of
the frightening 1992 magnitude 7.3Land-
ers and 1994 magnitude 6.7 Northridge
earthquakes, the USGS and SCEC jointly
published a guide (left) to increase public
awareness of earthquakes and quake
preparedness. This guide has helped resi-
dents understand their quake risks and
make their homes, workplaces, schools,
and families safer in earthquakes. More than 1.8 million copies of the guide
were distributed in southern California through schools, libraries, community
centers, and local government offices. More than 3.5 million copies of a
similar guide were distributed in the San Francisco Bay region after the 1989
magnitude 6.9 Loma Prieta earthquake. To commemorate the 10th anniversary
of the Northridge earthquake, updated English and Spanish guides will be
published in 2004.
has created a Web-based interface, called “Did You Feel It?,” to provide
Internet users with a means of reporting individual quake experiences that
are compiled into maps of ground-shaking intensity. This suite of products
provide the general public with rapid and comprehensive information
about U.S. and global earthquakes when they need it most.
During the past 10 years, the demand for USGS earthquake-information
products, including national and regional hazard maps and data from real-
time seismic monitoring, has skyrocketed. USGS information now directly
underpins local, state, and national earthquake loss-reduction and emergency
response efforts.
The Future of the USGS Earthquake Hazards Program
The USGS Earthquake Hazards Program is poised to build on its
accomplishments. The USGS will continue to improve on existing
earthquake monitoring, assessment, and research activities, with the
ultimate goal of providing the Nation with a new generation of earthquake
products that more effectively promote earthquake mitigation and better
facilitate earthquake response. At the heart of this effort will be a con-
tinued emphasis on delivering information that is useful, accessible, and
easily understood. By working closely with policymakers and emergency
planners, USGS will ensure that they have the most reliable and accurate
information possible about earthquake hazards and that USGS products
are tailored to their needs. USGS will participate in local and national
earthquake-mitigation planning exercises and help train emergency
responders, contingency planners, risk managers, the media, and others
in how to use earthquake-hazard assessments and real-time information
products. USGS will also continue to interact directly with communities
to help them understand their vulnerabilities to earthquakes and to plan
mitigation actions. Critical decisions for earthquake preparedness and
response, including those that ensure uninterrupted corporate and govern-
ment operations, are often made far from areas of high seismic hazard. So
*-
that informed and appropriate actions can be taken, USGS will continue to
work to ensure that earthquake-hazard information and products are useful
and familiar to decisionmakers, even in regions of low seismic hazard.
The USGS is committed to providing the Nation with new and useful
products to reduce earthquake losses and improve quake safety. However,
many needs cannot be met or opportunities seized under current funding
levels. Critical among those needs and opportunities are:
Completing the Advanced National Seismic System—A major obstacle
to further reducing loss of life and property in earthquakes is the present
scarcity of strong-motion recordings of actual ground-shaking levels in urban
areas and of the dynamic performance of structures and lifelines in quakes.
The Advanced National Seismic System (ANSS) is intended to address this
need by providing a nationwide network of least 7,000 sophisticated shaking
monitors placed both on the ground and in buildings, mostly in seismically
active urban areas. The closely spaced ANSS stations will be used to identify
areas with specific problems, such as high amplification and focusing of seis-
mic waves, and provide data crucial for finding cost-effective seismic-design
solutions.
One critical component of ANSS is the instrumentation of buildings,
bridges, and other structures. It is essential to have multiple structures in high-
hazard areas instrumented with arrays of seismometers so that engineers can
understand how different types of buildings respond to earthquake shaking.
These instruments will also provide crucial information on: -
• The coupling between building foundations and underlying soils,
• The role of torsion of columns in building shaking,
• The performance of commonly used structural systems, such as shear
walls combined with a moment-frame structure, and
• The ability of mathematical models to predict the performance of struc-
tures during strong shaking.
Another urgent need that will be addressed by ANSS is improved reli-
ability, timeliness, and usefulness of USGS real-time earthquake products for
In November 2002, the powerful
magnitude 7.9 Denali Fault
earthquake struck south-central
Alaska, rupturing the ground
beneath the zigzagging Trans-
Alaska Oil Pipeline. Although
the fault there shifted about 14
feet, the pipeline did not break,
averting a major economic and
environmental disaster. This
success was largely the result
of a design based on geologic
and engineering studies done by
the U.S. Geological Survey and
others. Alaska has the greatest
exposure to earthquake hazard
of any state. The impact of a
devastating quake in Alaska
could extend far beyond its bor-
ders, both by generating deadly
tsunamis and through economic
consequences.
rupture
Built-in
bends





SEISMIC-HAZARD INFORMATION HELPS ENSURE THE SURVIVAL OFSTRUCTURES AND LIFELINES
-
-
º-
RETROFITTED HIGHWAY OVERPASS
emergency-response purposes. ShakeMap, in particular, requires access to a
modern seismic network with digital strong-motion recording capabilities and
real-time telecommunications feeds. Currently, few urban areas in the United
States possess such a network. Full implementation of ANSS will allow
expansion of ShakeMap to all large U.S. metropolitan areas with moderate to
high seismic risk.
Acquiring essential data for expanded urban hazard assess-
ments—Most current USGS earthquake-hazard assessments are compiled
on regional or national scales. These estimates typically assume uniform firm
soil conditions, as opposed to the varying actual soil conditions beneath cities
and lifelines. At the scales required for urban planning and development,
assessments need to account for the amplifying effects of soils, as well as the
potential for ground failures, such as liquefaction and landslides.
USGS pilot urban assessments in Oakland, Seattle, and Memphis have
shown the usefulness of detailed urban seismic assessments. USGS must
expand this effort to include other urban centers at risk from earthquakes.
Central to this endeavor will be the acquisition of data on local geology, site
conditions, and ground motions needed to produce detailed urban seismic-
hazard maps. These data-acquisition efforts will require additional resources
that will in part be used to help support expanded partnerships with state geo-
logical surveys and local government agencies. As these urban hazard assess-
ments evolve, they will allow estimates to be made for potential earthquake
losses to buildings and critical lifelines. This is one of the keys to developing
cost-effective mitigation strategies to reduce future earthquake losses.
Expanding activities in the Eastern United States—The USGS Earth-
quake Hazards Program devotes approximately 75% of its resources to work
in the Western United States, primarily because earthquakes occur more
frequently there. However, history demonstrates that a catastrophic quake
could also strike a major city in the Eastern United States. Four damaging
earthquakes with magnitudes greater than 7 centered in the New Madrid,
Missouri, area struck the Mississippi Valley in 1811-12. Charleston, South
Carolina, was devastated by a magnitude 6.7 shock in 1886, and a magnitude
6 quake struck the Boston area in 1755.
USGS studies show that urban areas in the Eastern United States face far
greater damage and far more deaths in a quake of a given magnitude than
those in the West for several reasons: (1) For the same magnitude earthquake,
severe shaking affects a much larger area, (2) most structures are not designed
to resist earthquakes, and (3) population density is high and residents are not
routinely educated about seismic safety.
NON-RETROFITTED OVERPASS
U.S. Geological Survey (USGS) seismic-hazard informa-
tion is used by structural engineers to design structures
and lifelines, such as freeway overpasses, to help ensure
their survival in quakes. Over the past 25 years, USGS
and other scientists have discovered that quakes can
shake the ground much more violently than provided for
º, in earlier building codes. The California Department of
Transportation (Caltrans) has nearly completed a program
of retrofitting bridges and overpasses throughout the
- - State. In 1994, when the magnitude 6.7 Northridge earth-
- - quake struck Los Angeles, the success of this investment
was demonstrated. Retrofitted bridge columns in areas of
severe to violent shaking (such as those at left) survived
with minor or no damage, whereas non-retrofitted
overpass supports (such as the one at right) collapsed.
Caltrans is now beginning to use USGS “ShakeMaps" to
expedite their post-earthquake response, enabling emer-
gency managers to focus field inspections on the most
severely shaken areas. (Photos courtesy of Caltrans.)
USGS has been developing the understanding and methods that can form
the groundwork for a substantial effort in the East, where earthquake faults
are rarely exposed at the surface and the subsurface conditions beneath major
cities are poorly documented. More thorough and accurate assessment of the
seismic risk faced by major urban centers in the East will reveal the greatest
vulnerabilities and provide information that is essential to evaluating possible
mitigation strategies.
Expanding activities in Alaska–Alaska has the greatest exposure
to earthquake hazard of any state. Because of the relatively small urban
population, many people assume that the risk is low in comparison to the
rest of the country. However, the impact of a devastating quake in Alaska
can extend far beyond its borders, both by generating deadly tsunamis
(seismic sea waves) and through economic consequences. Alaska is a major
source of natural resources for the rest of the Nation, a major transportation
and commercial node of the Pacific Rim, and of significant importance to
national defense.
Capitalizing on new national facilities—As described in the 2003
National Research Council report, Living on an Active Earth: Perspectives
Ll Shaking felt Area of damage
1895
Magnitude
Magnitude
6.7
0 500 MILES
H-
0 500 KILOMETERS
In the Central and Eastern United States, earthquakes are felt over a broader area
than comparable-size quakes in the Western United States because of differences in
geology. Although only of magnitude 6, the earthquake that occurred near Saint Louis
in 1895 affected a larger area than the 1994 magnitude 6.7 Northridge, California,
quake, which caused $40 billion in damage and economic losses and killed 67 people.
A repeat of the 1895 earthquake could prove disastrous for the Midwest, where
structures are not as earthquake resistant as those in California.













-
------
Earthquakes pose a significant threat to urban areas in the Intermountain West.
For example, almost 75% of Utah's population lives near the Wasatch Fault.
Movement on this fault in past quakes has uplifted the Wasatch Range to form a
spectacular backdrop for the state's three largest cities, including Salt Lake City,
shown here. U.S. Geological Survey and Utah State Geological Survey scientists
have shown that this fault has repeatedly generated earthquakes of magnitude 7
or larger and will continue to do so in the future. Efforts to increase public aware-
ness of earthquake hazards in Utah have resulted in residents and community
leaders taking actions that will save lives and reduce damage in future quakes.
(Photo courtesy of the Salt Lake Convention and Visitors Bureau.)
on Earthquake Science, continued progress toward evaluating earthquake
hazards will increasingly require integrative, physics-based research involve
ing theoretical studies of processes controlling earthquake phenomena,
sophisticated numerical modeling, ground- and space-based field observa-
tions, and laboratory simulations. Recent and proposed U.S. Government
investments in major earth-science and engineering facilities include ANSS,
the NSF-coordinated EarthScope program (including the Plate Boundary
Observatory, USArray, and the San Andreas Fault Observatory at Depth), the
NSFNetwork for Earthquake Engineering Simulation (NEES), and a future
interferometric synthetic aperture radar (InSAR) satellite mission. These
facilities will be able to offer, for the first time, the breadth and depth of data
required to truly understand the physical nature of earthquakes.
The USGS will take advantage of these new data streams to conduct
earthquake-hazard-focused experiments on scales never before possible. To
improve long-term hazard assessments, USGS will also use these data to-
CREATING TIME-DEPENDENT EARTHOUAKE PROBABILI
º ºn
- - º -
º º - - -
sºn Francisco Bay Region
EARTHOUAKE PROBABILITY
- odds for one or more
ºf º magnitude 6.7 or greater
º earthquakes from 2000 to 2031. .
This result incorporates 14% odds
of quakes not on shown faults.
-
Stockton
Sºs
20 MILES º
º - º
0. 20 kiLOMETERS º Nº.
Q - 3. Cº.
o - - tºo.º.o-
Odds of magnitude º Santa Cruz Bºž º -
o Watsonville.º.º.
6.7 or greater quakes - º
before 2031 on the 3. º
indicated fault c --- º
º -
Increasing quake odds—-
along fault segments
- -
- - - -
- ---
in - --
- -
-ºn-
-
--
- -
- -
-
Time-dependent earthquake probability maps take into account the effects
of quake occurrence and fault interactions on the likelihood of future
quakes. In 1988, the first U.S. Geological Survey (USGS) map of this type
correctly identified the future site of the 1989 magnitude 6.9 Loma Prieta
earthquake. On the basis of research conducted since that quake, USGS
and other scientists conclude that there is a 62% probability of at least one
magnitude 6.7 or greater quake, capable of causing widespread damage,
striking the San Francisco Bay region before 2031. This periodically updated
information is widely disseminated to the public in both the print and broad-
cast media, as well as in USGS publications, and is being used to focus
preparedness efforts throughout the bay region.
earthquake hazard-assessment and mitigation tools. These tools will be used
to further reduce losses of life and property in the future earthquakes that are
certain to strike the Nation.
gether with advanced computational methods to simulate the multiple factors
controlling earthquakes within specific fault systems. A major goal will be
to understand the criteria for the occurrence of quakes within a fault system
and the impact of one quake on the system through the many processes that
transfer stresses. To determine the feasibility of short-term prediction of -
John R. Filson, Jill McCarthy, William L. Ellsworth, and Mary Lou Zoback
earthquakes, USGS will build new mathematical models of quake likelihood, Edited by
akin to weather-forecast models. Peter H. Stauffer and James W. Hendley II
Graphic design by
Conclusion Sara Boore, Susan Mayfield, and Stephen L. Scott, and Eleanor Omdahl
After 25 years of NEHRP the USGS Earthquake Hazards Program is the
world scientific leader in seismic-hazard studies. In implementing the results
of these studies to mitigate the effects of earthquakes, USGS has actively
collaborated with state geological surveys, emergency-response officials,
For further information contact:
U.S. Geological Survey, Mail Stop 905
12201 Sunrise Valley Drive
Reston, VA 20192
(703) 648-6714
http://earthquake.usgs.gov/
earthquake engineers, local governments, and the public. This collaboration
has resulted in dramatic improvements in earthquake preparedness and public
safety in the United States, but there is still much work to be done. By inte-
grating USGS earthquake information with data from new national initiatives, This Fact Sheet and any updates to it are available online at
http: bS.wr. - fact-sheet/fs()+7=63/
such as ANSS, USGS will be able to meet the need for a new generation of up //geopubs.wr usgs.gov/ “Tºº OF MICHIGAN
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