Did someone forget to pay the earthquake bill?

David D. Jackson

Published March 7, 2014, SCEC Contribution #11800

Paleo-seismicdata for California imply along term rate corresponding to a recurrence interval of decades, yet the rate during the instrumental seismic measurement era is considerably less. The third Uniform California Earthquake Recurrence Forecast (UCERF3) project bases estimated future earthquake rates largely on dates of observed paleo-seismic displacements at 31 sites on 13 named faults in California. The summed event rates for the whole ensemble of sites is about 0.1 per year. Allowing generously for occurrences of earthquakes that rupture multiple sites simultaneously, the event rate is on the order of 0.04 per year. Yet the most recent event date is 1910. Such a long open interval would be extremely unlikely for a Poisson process with that rate, which might be expected statewide even if individual faults ruptured in quasi-period events. Quasi-periodic behavior for the whole ensemble would make the discrepancy worse. Has some un-modeled force put tectonic processes into hibernation? If so, what is it, and how long can the Bear State sleep? Or is the relationship between paleo-seismic displacements and earthquakes not as close as assumed? What do you miss when you focus only on individual faults, rather than the ensemble?

Key Words
paleoseismology, recurrence, california, forecast

Jackson, D. D. (2014). Did someone forget to pay the earthquake bill?. Seismological Research Letters, 85(2), 365-558. doi: 10.1785/0220140014.

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