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Open-File Report 2012–1087

Seismic Hazard of American Samoa and Neighboring South Pacific Islands—Data, Methods, Parameters, and Results

By Mark D. Petersen, Stephen C. Harmsen, Kenneth S. Rukstales, Charles S. Mueller, Daniel E. McNamara, Nicolas Luco, and Melanie Walling

Thumbnail of and link to report PDF (19.5 MB)Abstract

American Samoa and the neighboring islands of the South Pacific lie near active tectonic-plate boundaries that host many large earthquakes which can result in strong earthquake shaking and tsunamis. To mitigate earthquake risks from future ground shaking, the Federal Emergency Management Agency requested that the U.S. Geological Survey prepare seismic hazard maps that can be applied in building-design criteria. This Open-File Report describes the data, methods, and parameters used to calculate the seismic shaking hazard as well as the output hazard maps, curves, and deaggregation (disaggregation) information needed for building design. Spectral acceleration hazard for 1 Hertz having a 2-percent probability of exceedance on a firm rock site condition (Vs30=760 meters per second) is 0.12 acceleration of gravity (1 second, 1 Hertz) and 0.32 acceleration of gravity (0.2 seconds, 5 Hertz) on American Samoa, 0.72 acceleration of gravity (1 Hertz) and 2.54 acceleration of gravity (5 Hertz) on Tonga, 0.15 acceleration of gravity (1 Hertz) and 0.55 acceleration of gravity (5 Hertz) on Fiji, and 0.89 acceleration of gravity (1 Hertz) and 2.77 acceleration of gravity (5 Hertz) on the Vanuatu Islands.

First posted August 7, 2012

For additional information contact:
Center Director, Geologic Hazards Science Center
U.S. Geological Survey
Box 25046, Mail Stop 966
Denver, CO 80225

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Suggested citation:

Petersen, M.D., Harmsen, S.C., Rukstales, K.S., Mueller, C.S., McNamara, D.E., Luco, Nicolas, and Walling, Melanie, 2012, Seismic hazard of American Samoa and neighboring South Pacific Islands—Methods, data, parameters, and results: U.S. Geological Survey Open-File Report 2012–1087, 98 p.





Seismic Sources

Ground Motion Model

Logic Tree for Seismic Hazard



References Cited


Appendix 1. Lessons of the M8.3 Tokachi-Oki and the M9 Tohoku Earthquakes

Appendix 2. Analysis of Ground Motion Prediction Equations

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