Poster #213, Ground Motions
Using historical intensity data to assess hazard map performance in California and beyond
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Poster Presentation
2020 SCEC Annual Meeting, Poster #213, SCEC Contribution #10569 VIEW PDF
ataset also includes new observations of intensity from archival research and oral history collection. Version 1 of the dataset includes 46,502 intensity observations for 62 earthquakes with estimated magnitudes ranging from 4.7 to 7.9. This data set, spanning 162 years, reveals that estimated maximum shaking throughout California has been lower than expected from seismic hazard models. This discrepancy is reduced, but persists, if historical intensity data for the largest earthquakes are smoothed to reduce the effects of spatial under-sampling. Possible reasons for this discrepancy include 1) other limitations of the CHIMP dataset, for example the omission of most earthquakes smaller than Mw 6; 2) systematic biases in the hazard models, and 3) the possibility that California seismicity throughout the historical period has been lower than the long-term average. Similar discrepancies between observed and predicted shaking have been documented for Italy and Japan (Stein et al., 2015; Brooks et al., 2016); we show preliminary analysis suggesting a similar result for Nepal. Taken at face value, these studies suggest that hazard could be systematically overestimated by modern PSHA.
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