- © 2007 by the Seismological Society of America
Ground-shaking hazard maps based on sound earth-science research are effective tools for mitigating damage from future earthquakes. Assuming that future earthquakes will occur on active faults or near previous events and that the ground shaking from these events will fall within the range of globally recorded ground motions leads to probabilistic hazard maps that predict ground-shaking potential across a region. Developing hazard and risk maps requires technical interactions between earth scientists and engineers to estimate the rate of potential earthquakes across a region, quantify likely ground-shaking levels at a site, and understand how buildings respond to strong ground shaking. For the past 25 years the U.S. Geological Survey (USGS) and California Geological Survey (CGS) have cooperated with government officials and professional organizations to incorporate hazard maps and other hazard products in public and corporate documents such as building codes, insurance rate structures, and earthquake risk mitigation plans (Algermissen and Perkins 1982; Frankel et al. 1996, 2002; Petersen et al. 1996).
Because these hazard products are used in making public-policy decisions, it is essential that the official USGS-CGS hazard models reflect the “best available science.” This qualification is also required by the statute that regulates the California Earthquake Authority, which provides most earthquake insurance in the state. To adequately represent the “best available science,” hazard maps need to be updated regularly to keep pace with new scientific advancements. The methodologies, computer codes, and input data used in developing these products need to be openly available for review and analysis. Input parameters and codes for current hazard maps may be obtained at http://earthquake.usgs.gov/hazmaps and http://www.consrv.ca.gov/cgs. At these Web sites a user may access documentation that describes methodologies and parameters, a relational database and tables that contain explanations of how the fault parameters and uncertainties were chosen, interactive …