U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2007–3073

Revised January 2010

understanding earthquake hazards in urban areas

St. Louis Area Earthquake Hazards Mapping Project

40°

38°

36°

34°

92° 90° 88° 86°

Springfield

St. Louis

Columbia

Huntsville

Evansville

Decatur

Clarksville

Little Rock

Memphis

Nashville

Indianapolis

Champaign

Terre Haute

Decatur

Jonesboro Jackson

Florence

Pine Bluff

Paducah

ILLINOIS

MISSOURI

INDIANA

KENTUCKY

ARKANSAS

TENNESSEE

MISSISSIPPI

ALABAMA

Wabash Valley

seismic zone

New Madrid

seismic zone

1909

1987

1838

1917

1965

1895

1865

1811

1812

1812

1891

1968

2002

        

      



 

What is earthquake hazard?

Earthquake hazard refers to a measure of the shaking, or ground motion, 

during earthquakes that can damage our 

built environment. The hazard depends 

on the magnitudes and locations of likely 

earthquakes, how often they occur, and 

the properties of the rocks and sediments 

that earthquake waves travel through. In 

the central United States, earthquakes 

occur along the New Madrid and Wabash 

seismic zones and in a zone of earthquakes that is scattered across southern 

Illinois and eastern Missouri.

Who uses earthquake 

hazard maps?

Public and private groups can use 

hazard maps for planning, mitigation, 

and response efforts to minimize losses 

resulting from earthquake shaking. 

Portfolio managers in the lending, insurance, and wealth management industries 

can use the maps to better manage risk 

exposure. Planning and zoning professionals can use the maps for hazard 

considerations in locating new development, critical facilities, and transportation 

corridors. Business continuity managers 

can use the maps to minimize earthquakerelated losses to their facilities, supply 

networks, and market share. The scale of 

the maps will not allow them to be used 

in a site-specific manner, but rather as a 

guide as to where more detailed studies 

are needed.

Earthquakes (circles) of the New Madrid and Wabash Valley seismic zones 

(orange patches). Red circles are earthquakes that occurred from 1974 to 2002. 

Green circles are earthquakes that occurred prior to 1974. Larger earthquakes 

are represented by larger circles. Yellow patches show larger urban areas.

St. Louis has experienced minor earthquake damage at least 12 times in the past 200 years. Because of this history and its 

proximity to known active earthquake zones, the St. Louis Area Earthquake Hazards Mapping Project will produce digital 

maps that show variability of earthquake hazards in the St. Louis area. The maps will be available free via the internet. 

They can be customized by the user to show specific areas of interest, such as neighborhoods or transportation routes. 

(Photograph looking west from a geophysical measurement site in east St. Louis, Mo., by Dave Hoffman.)

Earthquakes currently cannot be predicted, but scientists can estimate how strongly 

the ground is likely to shake as the result of an earthquake. Earthquake hazard maps 

provide one way of conveying such estimates. The U.S. Geological Survey (USGS), 

which produces earthquake hazard maps for the Nation, is working with local partners 

to develop detailed maps for urban areas vulnerable to strong ground shaking. These 

partners include the Missouri University of Science and Technology, Missouri Department of Natural Resources, Illinois State Geological Survey, Saint Louis University, 

Missouri State Emergency Management Agency, and URS Corporation.

Printed on recycled paper
Alluvium

(soft)

Floodplain

Loess

As much as

50 m thick

Soil

Soil

Bedrock

(hard)

Earthquake waves

can amplify in soft

soil such as alluvium

Upland

Upland

Mississippi

River

%g

Highest hazard

Lowest hazard

0

20

40

80

160

240

320+

St. Louis

area

EXPLANATION

ILLINOIS

MISSOURI

Making Earthquake 

Hazard Maps

Geologists map earth materials at 

the ground surface. Properties of these 

surficial materials, how deeply they 

extend, and properties of the bedrock 

below them are determined from measurements made in boreholes and cores 

drilled for construction projects and 

from oil, gas, mining, and water-well 

data. Information about the subsurface is 

obtained from imaging techniques, much 

like X-ray or ultrasound imaging is used 

to view the interior of the human body. 

These data are then combined to construct a three-dimensional (3-D) model of 

the layering of rock, soil, and alluvium.

Soil (weathered bedrock), loess, and 

alluvium layers change the way earthquake waves travel through them from 

an earthquake below. The 3-D model 

describes the layering beneath any location, and is used to calculate how the 

shaking from the waves will vary from 

place to place. For example, the sediments in the river floodplain may amplify 

some types of shaking more than at sites 

located on the upland areas.

The investigations done to produce 

the St. Louis area hazards maps will 

result in a variety of other products. 

Among these are maps of the surficial 

geologic materials as well as maps 

showing the likelihood of liquefaction. 

Liquefaction occurs when water-saturated 

sediments lose their cohesive strength 

during violent ground shaking. An online 

database of sediment properties determined in this project is also planned.

The diagram above is a block model showing simplified geology typical of the St. Louis area. Loess is 

a soft sediment carried and deposited by wind during the last glacial episode about 15,000 years ago; 

soils are soft materials often developed by weathering of bedrock; alluvium is soft river-deposited 

sediment that comprises most of the Missouri and Mississippi River floodplains. Structures located in 

the floodplains will likely experience stronger ground shaking and a greater likelihood of liquefaction. 

Bedrock is most commonly a hard 350 million-year-old limestone in the St. Louis area. Structures built 

on or near bedrock, such as in the upland areas out of the floodplains, will tend to have lower levels 

of earthquake ground shaking. Earthquake hazard maps, like the ones in development for St. Louis, 

provide needed information for the design of new structures and retrofitting of existing ones.

For more information contact:

Robert A. Williams

U.S. Geological Survey

Denver Federal Center 

P.O. Box 25046, MS 966 

Denver, CO 80225-0046

rawilliams@usgs.gov

St. Louis Hazard Mapping website:

http://earthquake.usgs.gov/regional/

ceus/urban_map/st_louis/index.php

Earthquake Hazards Program:

http://earthquake.usgs.gov/

Partners: Center for Earthquake Research and Information, Central U.S. Earthquake Consortium, Illinois State Geological Survey, Missouri S&T, 

Missouri Department of Natural Resources, Missouri State Emergency Management Agency, Saint Louis University, URS Corporation. 

The inset box shows a preliminary seismic hazard map for the St. Louis, Mo., area, recently 

completed by Chris Cramer at CERI University of Memphis and Deniz Karadeniz and Dave 

Rogers at Missouri University of Science and Technology. The differences in seismic hazard 

between the national-scale 

and St. Louis area maps 

result directly from including 

the effects of near-surface 

soft sediments in the urbanscale map. Earthquake 

hazard maps such as these 

will help the region prepare 

for future earthquakes by 

showing, in detail, the potential variability of earthquake 

ground motion. 

The 

national 

seismic hazard 

map shows the 

level of shaking in percent “g”

(100 percent g is equivalent to the acceleration of a falling object caused by gravity).