U.S. Geological Survey (USGS) national seismic-hazard map, earthquake hazards exist throughout the United States. USGS national and regional seismic-hazard maps forecast the amount of shaking expected over specified time periods. Many parts of the Central and Eastern United States have moderate to high long-term hazard, even though they have not experienced recent large quakes. Successive updates of USGS seismic-hazard maps are used to revise building codes and are also widely used by structural engineers and government agencies. The next generation of such maps will provide time-dependent probabilities that take into account the effects of prior quake occurrence on future earthquake likelihood.
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