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 moder-
ate (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 dis-
placed 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 Manage-
ment Agency has estimated future
annual earthquake losses in the
United States at $5.6 billion a year.

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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 damag-
ing ground shaking will be at a
particular location from a given
earthquake?

What is the cost-effectiveness of
different mitigation technologies?

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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 Mi-
choa-can, Mexico, 1,240 miles away.

Alaska is the most earthquake-prone State and one of the most seismically ac-
tive 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:

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• 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., earth-
quake on December 22, 2003. Two people
were killed trying to get out of the store dur-
ing the earthquake (FEMA photograph/Dane
Golden).

This business in Seattle was heavily dam-
aged 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 respond-
ers 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 net-
work of sophisticated shaking monitors
placed both on the ground and in build-
ings in urban areas.

ANSS stations will provide better data
crucial for finding cost-effective seismic-
design 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 cit-
ies, 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 prod-
ucts that facilitate more effective mitiga-
tion 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