Technical problems in the construction of a map to zone the earthquake ground-shaking hazard in the United States

Zoning of the earthquake ground-shaking hazard — the division of a region into geographic areas having a similar relative severity or response to ground shaking — has been a goal in the United States for about fifty years. During this period, two types of ground-shaking hazard maps have been constructed. The first type assumes that, except for scaling differences, approximately the same effects that occurred in historic earthquakes will occur in future earthquakes. The second type integrates historic seismicity data and geologic information and uses probabilistic concepts to estimate the characteristics of future ground shaking within specific exposure times. Construction of zoning maps on both a national and regional scale requires innovative research and good data to resolve technical issues about seismicity, the earthquake source, seismic wave attenuation, and local ground response. Because of unresolved issues, implementation in building codes has proceeded fairly slowly.