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A Geodesy‐ and Seismicity‐Based Local Earthquake Likelihood Model for Central Los Angeles

Chris Rollins, & Jean-Philippe Avouac

Published March 28, 2019, SCEC Contribution #9380

We estimate time‐independent earthquake likelihoods in central Los Angeles using a model of interseismic strain accumulation and the 1932–2017 seismic catalog. We assume that on the long‐term average, earthquakes and aseismic deformation collectively release seismic moment at a rate balancing interseismic loading, mainshocks obey the Gutenberg‐Richter law (a log linear magnitude‐frequency distribution [MFD]) up to a maximum magnitude and a Poisson process, and aftershock sequences obey the Gutenberg‐Richter and “Båth” laws. We model a comprehensive suite of these long‐term systems, assess how likely each system would be to have produced the MFD of the instrumental catalog, and use these likelihoods to probabilistically estimate the long‐term MFD. We estimate Mmax = 6.8 + 1.05/−0.4 (every ~300 years) or Mmax = 7.05 + 0.95/−0.4 assuming a truncated or tapered Gutenberg‐Richter MFD, respectively. Our results imply that, for example, the (median) likelihood of one or more Mw ≥ 6.5 mainshocks is 0.2% in 1 year, 2% in 10 years, and 18–21% in 100 years.

Rollins, C., & Avouac, J. (2019). A Geodesy‐ and Seismicity‐Based Local Earthquake Likelihood Model for Central Los Angeles. Geophysical Research Letters, 46(6), 3153-3162. doi: 10.1029/2018GL080868.