The U.S. Geological Survey (USGS) Earthquake Hazards Program monitors 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 challenges 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 quantitative 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 earthquake 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 preparedness, 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 

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 communities 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 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 organizations in the private sector. USGS also works closely with the other 

NEHRP agencies (FEMA, NSF, and the National Institute of Standards 

and Technology) and with non-NEHRP agencies, such as NASA, 

NOAA, and USAID.

REDUCING EARTHQUAKE LOSSES THROUGHOUT THE UNITED STATES

In 1977, Congress authorized the 

creation of the National Earthquake Hazards Reduction Program 

(NEHRP) to improve the Nation’s 

understanding of earthquake hazards and to mitigate their effects. 

Earthquakes are the most costly 

natural hazard faced by the United 

States. Twenty-fi ve years of work by 

the U.S. Geological Survey (USGS), 

in close cooperation with the three 

other NEHRP agencies, has yielded 

major advances in earthquake preparedness 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 NEHRP to protect 

lives and property in the future 

earthquakes that are certain to 

strike the United States.

The USGS Earthquake Hazards Program in NEHRP—

Investing in a Safer Future

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 specifi ed 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 

occurrence on future earthquake likelihood.

U.S. Department of the Interior

U.S. Geological Survey

USGS Fact Sheet 017-03 

2003
codes have now been adopted by jurisdictions in 37 states. Thus, the USGSproduced 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 guidelines, 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.

Accomplishments and Impacts of the USGS Earthquake 

Hazards Program

Over the past 25 years, NEHRP has made the Nation safer from the ravages 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 seismichazard 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 Management 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 

EARTHQUAKE DETECTIVE WORK REVEALS PREVIOUSLY UNKNOWN HAZARDS

In the 1980’s, U.S. Geological Survey (USGS) scientists discovered the 

first evidence that very large earthquakes have repeatedly struck the Pacific 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 1990’s, 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 scientists pieced 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 

Northwest on the evening of January 26, 1700, releasing 30 times as 

much energy as the largest quake ever recorded in California.

 When this potential for magnitude 9 earthquakes offshore Washington 

and Oregon was recognized, USGS and the Federal Emergency 

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.

UNDERSTANDING THE PHYSICS OF EARTHQUAKES

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 fi eld 

tests, have led to new theories about the physics of faulting and the role of 

fl uids in quake generation. USGS is now poised to directly test these theories not just on laboratory scale models (left) but also at a depth of 2.5 miles 

in the San Andreas Fault (right) at Parkfi eld, California. There, the San Andreas 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.

SAN ANDREAS FAULT MODEL

USGS SHAKING-HAZARD MAPS

2
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 earthquake location maps, automatic Web pages with information on signifi -

cant events, and aftershock probability estimators. Additionally, USGS 

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 

“SHAKEMAP”—A NEW TECHNOLOGY TO AID EMERGENCY RESPONSE

Discovering active faults in 

thickly vegetated regions, such 

as the Puget Sound area of 

Washington (photo), is very 

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 highresolution 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.

DISCOVERING HIDDEN FAULTS

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 developed 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.

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 earthquakes. The resulting records reveal how structural systems perform in 

quakes and how shaking is amplifi ed on upper fl oors, as demonstrated 

here by records from the tower during the1989 Loma Prieta earthquake. 

In that quake, 63 people were killed when other structures collapsed. A 

major objective of the Advanced National Seismic System (ANSS) 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.

INSTRUMENTED BUILDINGS PROVIDE CRUCIAL DATA

(Courtesy of Kitsap County Public Utility District.)

3
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 realtime 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 continued 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 government 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 seismic 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 highhazard 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 structures during strong shaking.

Another urgent need that will be addressed by ANSS is improved reliability, 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 TransAlaska 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 borders, both by generating deadly 

tsunamis and through economic 

consequences.

HELPING THE PUBLIC PREPARE FOR EARTHQUAKES

The U.S. Geological Survey (USGS) and 

the Southern California Earthquake 

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 subsurface geologic structures. In the wake of 

the frightening 1992 magnitude 7. 3 Landers 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 residents 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 offi ces. 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.

4
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 assessments—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 seismichazard maps. These data-acquisition efforts will require additional resources 

that will in part be used to help support expanded partnerships with state geological surveys and local government agencies. As these urban hazard assessments 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 Earthquake 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.

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 

U.S. Geological Survey (USGS) seismic-hazard information 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 

in earlier building codes. The California Department of 

Transportation (Caltrans) has nearly completed a program 

of retrofi tting bridges and overpasses throughout the 

State. In 1994, when the magnitude 6.7 Northridge earthquake struck Los Angeles, the success of this investment 

was demonstrated. Retrofi tted bridge columns in areas of 

severe to violent shaking (such as those at left) survived 

with minor or no damage, whereas non-retrofi tted 

overpass supports (such as the one at right) collapsed. 

Caltrans is now beginning to use USGS “ShakeMaps” to 

expedite their post-earthquake response, enabling emergency managers to focus fi eld inspections on the most 

severely shaken areas. (Photos courtesy of Caltrans.)

SEISMIC-HAZARD INFORMATION HELPS ENSURE THE SURVIVAL OF STRUCTURES AND LIFELINES

RETROFITTED HIGHWAY OVERPASS NON-RETROFITTED OVERPASS

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.

5
on Earthquake Science, continued progress toward evaluating earthquake 

hazards will increasingly require integrative, physics-based research involving theoretical studies of processes controlling earthquake phenomena, 

sophisticated numerical modeling, ground- and space-based field observations, 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 

NSF Network 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 together 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 

earthquakes, USGS will build new mathematical models of quake likelihood, 

akin to weather-forecast models. 

Conclusion

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, 

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 integrating USGS earthquake information with data from new national initiatives, 

such as ANSS, USGS will be able to meet the need for a new generation of 

Earthquakes pose a signifi cant 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 awareness 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.)

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/

This Fact Sheet and any updates to it are available online at

http://geopubs.wr.usgs.gov/fact-sheet/fs017-03/

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.

Printed on recycled paper

John R. Filson, Jill McCarthy, William L. Ellsworth, and Mary Lou Zoback

Edited by

Peter H. Stauffer and James W. Hendley II

Graphic design by

Sara Boore, Susan Mayfi eld, and Stephen L. Scott, and Eleanor Omdahl

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 fi rst U.S. Geological Survey (USGS) map of this type 

correctly identifi ed 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 broadcast media, as well as in USGS publications, and is being used to focus 

preparedness efforts throughout the bay region.

CREATING TIME-DEPENDENT EARTHQUAKE PROBABILITY MAPS

6