Investigation into the Historic Seismicity of Central California

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9506622 DREGER This research is to extend modern techniques of analysis of large earthquakes in southern and central California back to historical times when only analog seismographic recordings were available. While many of these regions are currently quiet, especially off of the San Andreas fault, several historic large earthquakes have occurred there and these are important to the estimation of seismic hazard. The longest-lived seismic stations in California are the Berkeley BRK and MHC (since 1887), and the Caltech PAS and SBC (since 1927) stations. In addition, seismograms will be obtained from other regional and teleseismic sites such as the De Bilt, Netherlands and the Florissant, Missouri observatories. The technique involves the use of recent earthquakes recorded by modern networks to compare with the historic data to obtain relative locations, magnitude scaling, and to calibrate paths to each station. The resulting calibrated Green's functions will be used to model the historic events for source depth, scalar seismic moment, fault orientation and potential source complexity in the larger historic earthquakes. This research is a component of the National Earthquake Hazard Reduction Program. ***