Can Earthquake Clustering Explain the Paleo-Event Hiatus in California?

Date: 4/24/2019

Time: 05:15 PM

Room: Pike

There has been a notable absence of large earthquakes in the last century in California, particularly on the highest slip-rate faults. This lull was noted by Jackson (2014), who argued that the observed data precluded Poissonian or lognormal earthquake occurrence, provided that earthquake times between distant sites were not correlated. We analyze the statistical significance of the hiatus given that earthquake times between sites may in fact be correlated by elastic rebound and aftershock-driven clustering effects. We look at three models, the UCERF3-TD model, which includes elastic rebound effects; the UCERF3-ETAS model, which includes both elastic rebound and aftershock clustering; and a critical ETAS model that includes aftershock clustering with a “long reach” in both space and time. The critical ETAS model has the highest probability of an extended hiatus affecting all paleoseismic sites, with a 6% chance of 1 or fewer paleo-events in a given century. Thus, we find that earthquake clustering does make the paleo-event hiatus more likely to occur; so, one explanation for the observed paleo-hiatus in California is that large events on the major faults, taken together, are clustered in time.

Presenting Author: Morgan Page

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