This map shows relative shaking hazards in the United States and Puerto Rico. During a 50-

year time period, the probability of strong shaking increases from very low (white), to moderate (blue, green, and yellow), to high (orange, pink, and red). Map not to scale. Source: USGS.

USGS Science Helps Build Safer Communities

Earthquake Hazards—A National Threat

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2006–3016 

March 2006

The upper level of this two-level section of 

Interstate 880 in Oakland, Calif., collapsed 

during the magnitude 6.9 Loma Prieta, Calif., 

earthquake on October 17, 1989. Forty-one 

motorists were killed in the collapse (USGS 

photograph).

A Widespread Danger

Earthquakes are one of the most 

costly natural hazards faced by the 

Nation, posing a significant risk to 75 

million Americans in 39 States.

The risks that earthquakes pose to 

society, including death, injury, and 

economic loss, can be greatly reduced 

by (1) better planning, construction, and 

mitigation practices before earthquakes 

happen and (2) providing critical and 

timely information to improve response 

after they occur. 

As part of the multiagency National 

Earthquake Hazards Reduction Program, 

the U.S. Geological Survey (USGS) 

has the lead Federal responsibility to 

provide notification of earthquakes in 

order to enhance public safety and to 

reduce losses through effective forecasts 

based on the best possible scientific 

information.

Science Helps Prepare the Nation

The USGS supports regional, national, 

and global seismic-monitoring networks, 

studies why earthquakes occur and how 

they shake the ground, assesses the 

Earthquake hazards in the United States and Puerto Rico

Printed on recycled paper

More than 75 million Americans in 

39 States face significant risk from 

earthquakes.

The magnitude 6.7 Northridge, 

Calif., earthquake in January 1994 

killed 33, injured 9,000, and displaced over 20,000 people.

Repeats of historic U.S. earthquakes, 

such as the 1906 San Francisco 

earthquake or the 1811–1812 New 

Madrid earthquakes, could cause up 

to $500 billion in damage.

The Federal Emergency Management Agency has estimated future 

annual earthquake losses in the 

United States at $5.6 billion a year.

•

•

•

•

The USGS is working to answer:

Which faults are the most likely to 

produce damaging earthquakes?

What controls the time between 

earthquakes on a given fault?

What keeps one earthquake small 

and lets another grow to hundreds 

of miles?

What controls the interactions 

among earthquakes?

What determines how damaging ground shaking will be at a 

particular location from a given 

earthquake?

What is the cost-effectiveness of 

different mitigation technologies? 

•

•

•

•

•

•

Earthquake Impacts USGS Science Priorities
The largest recorded earthquake in the United States was a magnitude 9.2 

earthquake in Prince William Sound, Alaska, on March 28, 1964.

In 1985, a swimming pool at the University of Arizona in Tucson lost water 

from sloshing, or a “seiche,” caused by a magnitude 8.1 earthquake in Michoa-can, Mexico, 1,240 miles away.

Alaska is the most earthquake-prone State and one of the most seismically active regions in the world, experiencing a magnitude 7 earthquake almost every 

year and a magnitude 8 or greater earthquake every 14 years (on average).

In the United States, there are an average of six magnitude 6 or greater and 57 

magnitude 5 or greater earthquakes each year.

Twenty-six urban areas in the United States are at risk of significant seismic 

activity:

•

•

•

•

• A vehicle, seen near the left edge of this 

image, was crushed under this collapsed 

storefront in Paso Robles, Calif., during the 

magnitude 6.5 San Simeon, Calif., earthquake on December 22, 2003. Two people 

were killed trying to get out of the store during the earthquake (FEMA photograph/Dane 

Golden).

This business in Seattle was heavily damaged during the magnitude 6.8 Nisqually, 

Wash., earthquake on February 28, 2001. 

About 400 people were injured during 

the earthquake (FEMA photograph/Kevin 

Galvin).

hazard level across the Nation, promotes 

loss-reduction measures using these 

results, and provides crucial scientific 

information to help emergency responders when earthquakes occur. 

The USGS is gathering data for 

expanded urban hazard assessments on a 

local scale to understand how varying soil 

conditions affect the shaking and damage 

within cities and at critical lifelines. 

The USGS is also conducting research 

to better understand how these hazards 

change with time.

Although earthquakes occur less 

frequently in the Eastern United States, 

studies show that urban areas in the East 

could face devastating losses because 

severe shaking would affect a larger area 

than a similar earthquake in the Western 

United States. Also, most structures in the 

Eastern United States are not designed to 

resist earthquakes. 

Population density is also high in the 

Eastern United States, and residents are 

not as well prepared for earthquakes as 

communities in the West. 

In Alaska and the Pacific Northwest, 

the effects of a destructive earthquake 

can extend well beyond local impact by 

potentially creating far-reaching tsunamis 

and resulting in economic losses that 

could exceed any that have occurred from 

previous earthquakes or tsunamis.

The USGS Is Networking

The USGS and university and State 

Geological Survey partners have begun to 

install and operate the Advanced National 

Seismic System (ANSS), a national network of sophisticated shaking monitors 

placed both on the ground and in buildings in urban areas. 

ANSS stations will provide better data 

crucial for finding cost-effective seismicdesign solutions for homes, buildings, 

bridges, and other structures. 

In cities where ANSS is in place, such 

as Los Angeles, the USGS has begun 

producing maps within minutes of an 

earthquake showing the distribution and 

severity of ground shaking in or near the 

urban center. These “ShakeMaps” form 

the basis for emergency response by cities, States, Federal agencies, and critical 

lifeline operators. 

The USGS will continue to improve 

on existing earthquake monitoring, 

assessment, and research activities, with 

the ultimate goal of providing new products that facilitate more effective mitigation and response. 

Albuquerque, N. Mex.

Anchorage, Alaska

Boise, Idaho

Boston, Mass.

Charleston, S.C.

Chattanooga-Knoxville 

Tenn.

Eugene-Springfield, 

Oreg.

Evansville, Ind.

Fresno, Calif.

Las Vagas, Nev.

Los Angeles, Calif.

Memphis, Tenn.

New York, N.Y.

Portland, Oreg.

Provo-Orem, Utah

Reno, Nev.

Sacramento, Calif.

St. Louis, Mo.

Salinas, Calif.

Salt Lake City, Utah

San Diego, Calif. 

San Francisco-Oakland, 

Calif.

San Juan, P.R.

Santa Barbara, Calif. 

Seattle, Wash.

Stockton-Lodi, Calif.

Earthquake Facts

http://earthquake.usgs.gov/

http://www.usgs.gov/

For More Information