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< Historic Iowa Earthquakes

Red ball iconIowa Earthquakes


Map of epicenters
Only 13 earthquakes with epicenters in Iowa are known in historic times. The first known occurrence was in 1867 near Sidney in southwest Iowa; the most recent occurrence was in 2004 near Shenandoah in SW Iowa. The largest Iowa earthquake (Mercalli magnitude VI) occurred near Davenport in southeast Iowa in 1934. Only the most recent of these events was instrumentally recorded.   (Click here to view map of historic Iowa epicenters.)


  UBC map

Uniform Building Code Seismic Hazard Map                 

Most of Iowa falls within Uniform Building Code (UBC) seismic zone 0, with the southern tip of Lee County, in southeast Iowa, and portions of western Iowa falling within seismic zone 1. Most of Fremont County, in southwest Iowa, lies in seismic zone 2A. (Click here to view map.)

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Seismic map

Seismic Impact Zones                 

Seismic Impact Zones are regions with a 90% or greater probability that the acceleration (due to a seismic event) will exceed 0.10 g (or 10% of the Earth's gravitational pull) in 250 years.  These areas were delineated by Algermissen and others (1982, U.S. Geological Survey Open File Report 82-1033) based on probabilistic estimates of the maximum acceleration and velocity in rock.  The zones are delineated on Plate 3 of this report.  Federal regulations for hazardous waste landfills state that new units and lateral expansions shall not be located in seismic impact zones, unless it can be demonstrated that the facility is designed to resist the event. (Click here to view map of Seismic Impact Zones in the Iowa area.)

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National Hazards map

USGS National Seismic Hazard Mapping Project

The U.S. Geological Survey National Seismic Hazard Mapping Program has produced maps showing earthquake ground motions that have a specified probability of being exceeded in 50 years. These ground motion values are used for reference in construction design for earthquake resistance. The ground motion values can also be used to assess relative hazard between sites, when making economic and safety decisions.  To view the USGS maps click here.   To learn more about preparing for earthquakes to minimize property damage and help save lives, click here.

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New Madrid seismic zone

New Madrid (Mississippi River ) Earthquake Zone     

In the winter of 1811-1812, the central Mississippi Valley was struck by three of the most powerful earthquakes in U. S. history. Even today, this region has more earthquakes than any other part of the United States east of the Rocky Mountains. Government agencies, universities, and private organizations are working to increase awareness of the earthquake threat and to reduce loss of life and property in future shocks. (Click here to view map in detail.)

Description of the New Madrid Earthquakes of 1811-1812

Iowa Perspective on Midwest Earthquakes

The Mississippi Valley - "Whole Lotta Shakin' Goin' On"

Descriptions of the New Madrid Earthquake by The Virtual Times
(Description 1 and Description 2)

For more information on earthquakes, visit the Saint Louis University Earthquake Center

        For more information contact:


           Ray Anderson
           phone: (319) 335-1575
           e-mail : Raymond.Anderson@dnr.iowa.gov