Toward a Database of Consistently Reinterpreted Intensities in California

Date: 4/26/2019

Time: 09:30 AM

Room: Pike

Historical seismic intensity data spanning long time intervals have been used to assess the performance of probabilistic seismic hazard assessments (PSHA). The short time since hazard maps began to be made is a challenge for assessing how well they work. Hindcasts offer long records, but are not true tests, as they compare maps to data that were available when the map was made. Historical intensity data are somewhat independent of the PSHA models because they were often not considered directly in the map’s creation, so hindsights give useful insight into the strengths and weaknesses of PSHA maps. As part of an effort to create a consistently reinterpreted maximum observed seismic intensity database for California with which to asses PSHA performance, we investigate the 1952 Kern County, California earthquake. Intensity data provide a measure of ground motion through first-hand accounts of shaking during an earthquake. These data reveal the distribution of ground motions in detail. Practices for assigning intensity values have changed over time, warranting reinterpretation of the intensity distributions of historic earthquakes. Although intensity interpretations have several sources of uncertainty, they are often the primary data available for historic and early instrumental earthquakes. For the Kern County earthquake we use the data and intensity prediction equations to arrive at an intensity magnitude of M_I 7.2 ± 0.2. This estimate is on the lower end of previously published instrumental estimates.

Presenting Author: Leah Salditch

Authors