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Open-File Report 2008–1128

Documentation for the 2008 Update of the United States National Seismic Hazard Maps

By Mark D. Petersen, Arthur D. Frankel, Stephen C. Harmsen, Charles S. Mueller, Kathleen M. Haller, Russell L. Wheeler, Robert L. Wesson, Yuehua Zeng, Oliver S. Boyd, David M. Perkins, Nicolas Luco, Edward H. Field, Chris J. Wills, and Kenneth S. Rukstales

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Open-File Report
2008-1128 PDF (17.8 MB)

The 2008 U.S. Geological Survey (USGS) National Seismic Hazard Maps display earthquake ground motions for various probability levels across the United States and are applied in seismic provisions of building codes, insurance rate structures, risk assessments, and other public policy. This update of the maps incorporates new findings on earthquake ground shaking, faults, seismicity, and geodesy. The resulting maps are derived from seismic hazard curves calculated on a grid of sites across the United States that describe the frequency of exceeding a set of ground motions. The USGS National Seismic Hazard Mapping Project developed these maps by incorporating information on potential earthquakes and associated ground shaking obtained from interaction in science and engineering workshops involving hundreds of participants, review by several science organizations and State surveys, and advice from two expert panels.

The National Seismic Hazard Maps represent our assessment of the "best available science" in earthquake hazards estimation for the United States (maps of Alaska and Hawaii as well as further information on hazard across the United States are available on our Web site at

Version 1.1

Posted May 2008

Suggested citation:

Petersen, Mark D., Frankel, Arthur D., Harmsen, Stephen C., Mueller, Charles S., Haller, Kathleen M., Wheeler, Russell L., Wesson, Robert L., Zeng, Yuehua, Boyd, Oliver S., Perkins, David M., Luco, Nicolas, Field, Edward H., Wills, Chris J., and Rukstales, Kenneth S., 2008, Documentation for the 2008 Update of the United States National Seismic Hazard Maps: U.S. Geological Survey Open-File Report 2008–1128, 61 p.



General Methodology

Seismicity-Derived Hazard Component

Fault Sources

Attenuation Relations

Central and Eastern United States

Source Model: Seismicity-Derived Hazard Component


Maximum Magnitude

Smoothed-Gridded Seismicity

Uniform Background Zones

Special Zones

Source Model—Faults

New Madrid Seismic Zone

Rupture Sources


Earthquake Recurrence

Charleston, South Carolina, Seismic Zone

Meers Fault, Oklahoma, and Cheraw Fault, Colorado

Ground-Motion Relations

Western United States

Source Model—Seismicity Derived Hazard Component


Maximum Magnitude

Smoothed-Gridded Seismicity

Uniform Background Zones

Special Zones

Source Model—Geodetically Derived Areal Source Zones (C Zones)

Source Model—Faults


Earthquake Recurrence

Intermountain West Fault Sources

Pacific Northwest—Cascadia Fault Sources

California Fault Sources

Ground-Motion Relations

Crustal Faults

Subduction Zone/Plate Interface

Subduction Zone—In-Slab

Results of the Seismic Hazard Calculations

Central and Eastern United States Maps

Western United States Maps

Conclusions and Proposed Future Improvements to Maps



Appendixes A–K

A. Depth to the Top of Rupture (Ztor) for Western United States Faults

B. Fault Distances to Nonplanar Fault

C. Distance to a Fault with Random Strike

D. Modeling Dip-Slip Background Sources

E. The Gutenberg-Richter Part of the Magnitude-Frequency Distribution for Western United States Faults

F. New Madrid Temporal Cluster Model

G. Parameters for Faults in the Intermountain West

H. Parameters for Faults in the Pacific Northwest

I. Parameters for Faults in California

J. Fault-Model Changes in the Western United States

K. Cascadia Subduction Zone


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