Quantifying CISN Shakemap Uncertainty

by Kuo-wan Lin, David J. Wald, Bruce Worden and Anthony F. Shakal

Lin, Kuo-wan, David J. Wald, Bruce Worden and Anthony F. Shakal (2005). Quantifying CISN Shakemap Uncertainty. SMIP05 Seminar on Utilization of Strong-Motion Data, p. 37 - 50.

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Efforts underway to quantify uncertainties associated with ShakeMap ground motions through efforts by the California Integrated Seismic Network (CISN) ShakeMap Working Group are discussed. There are multiple sources of uncertainty in producing a ShakeMap, including sparse ground motion measurements, approximate representation of fault finiteness and directivity, empirical ground motion predictions, numerical interpolation, and site corrections. These ground motion uncertainty measures are critical for evaluating the range of possible losses and allow users to associate appropriate levels of confidence when using rapidly produced ShakeMaps as part of their post-earthquake critical decision making process. We quantify the uncertainties of the maps on a point-by-point basis, by combining the separate, but related, contributions of uncertainty for each ShakeMap parameter as a function of location on the map. Finally, we show examples of results of estimates of uncertainty for ShakeMap for earthquakes in California with/without defined fault traces. We discuss future developments and plans for integration of these uncertainty measures, both quantitative and qualitative, into the online system and user interfaces of ShakeMap.