Every six years the U.S. Geological Survey (USGS) produces an updated set of seismic hazard maps for the United States. These National Hazard Maps show the estimated probabilities of different levels of ground shaking by location, and the maps are used by engineers for building and other structural designs in earthquake-prone areas. The maps also provide guidance for local building codes and inform the earthquake catastrophe models.
Executive SummaryIn a 2014 report on earthquake forecasting, "The Third Uniform California Earthquake Rupture Forecast (UCERF3)," U.S. Geological Survey scientists and collaborating partners in southern California recognize the possibilities of multi-fault ruptures and backgroundevents, where there are no known faults and historical events. While the larger magnitude multi-fault scenarios are the most significant methodological change from a scientific perspective, it is the background events, which can happen anywhere, that have more implications for insurers, according to risk expert Karen Clark.
The most recent report was released in 2014 and will eventually provide the basis for all of the U.S. earthquake models. Because of added complexities, it’s taking the modeling companies longer than usual to incorporate the updated information. This article explains the new report, why it’s more complex and the most important implications for senior insurance executives.
The first thing for decision-makers to understand is that when the maps are updated, it doesn’t mean there are radical new theories or significant changes in the scientific understanding of earthquakes. Rather, the updated maps are “snapshots” of the ongoing research in earthquake hazard at particular points in time. The maps have been updated every several years with the most current research at the time, and more scientists are contributing to successive reports, which means a wider range of expert opinion (and wider uncertainty) is being accounted for.