Group A, Poster #219, Ground Motions

Which earthquakes are the most damaging? An examination of community-collected ‘Did You Feel It’ data in California, USA

Jenna M. Chaffeur, Sarah E. Minson, Jessie K. Saunders, Annemarie S. Baltay, Susan E. Hough, Elizabeth S. Cochran, Sara K. McBride, Vince Quitoriano, & Luke Blair
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Poster Presentation

2022 SCEC Annual Meeting, Poster #219, SCEC Contribution #12122 VIEW PDF
‘When will I feel the big one?’ is a question that earthquake scientists are all too familiar with. But while waiting for the big one to occur, people will experience several smaller magnitude earthquakes. The combination of ground motion variability with the high frequency of occurrence of smaller magnitude earthquakes will result in most instances of ground shaking (including hazardous shaking) being caused by smaller magnitude earthquakes than by less frequent very large magnitude events (Minson et al., 2021). But does this mean that most damage is caused by anomalous smaller magnitude earthquakes? To answer this question, we explore reports of earthquake damage and felt shaking experienc...e using a catalog of community-collected intensity values from the U.S. Geological Survey’s ‘Did You Feel It?’ (DYFI) product. We consider all available 1-km resolution DYFI reports from M3+ earthquakes in locations that contribute to seismic hazard in California, defined as all events inside California or within 100 km of the California state boundary by the third Uniform California Earthquake Rupture Forecast (UCERF3) and Regional Earthquake Likelihood Models (RELM). This yields over 600,000 geospatial Community Decimal Intensity (CDI) data points from over 4,000 earthquakes. This data set includes not only earthquakes that have occurred since the DYFI program began in 1999, but also historical earthquakes going back to the 1933 M6.4 Long Beach, California, earthquake. We analyze CDI values from the DYFI database and explore the relative impacts of larger and smaller magnitude earthquakes.

As with the findings from Minson et al. (2021), the results of this study will not change total hazard as depicted in the United States National Seismic Hazard Model, which already considers ground motion variability. However, our work has potential to shift individual perception of risk away from the ambiguous ‘big one’ and towards more probable experiences with more frequent smaller earthquakes. Such a shift might not only better represent the types of earthquake hazards people will experience in their lifetimes, but also decrease fatalism and encourage people to prepare for earthquakes (e.g., McClure et al., 2001; Becker et al., 2013; McBride, 2017).