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Geophysics Department Seminar - William Frank: Self-diagnostic low-frequency earthquakes and the slow slip that drives them

Date and Time: 
November 29, 2018 -
12:00pm to 1:15pm
Mitchell 350/372
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Event Sponsor: 
Geophysics Department

Speaker: Dr. William Frank - Assistant Professor, University of Southern California

Low-frequency earthquakes (LFEs) are repetitive seismic events that accompany slow slip on plate boundaries, the cyclic slow aseismic release of built-up tectonic stress. Recent work has shown that LFE activity is a useful indicator of when slow slip occurs, even when its geodetic signature is buried in the noise. It is however difficult to determine whether the evolution of LFE activity reflects the dynamics of aseismic slip, because the two observations are made on entirely different time scales: GPS surface displacement is sampled daily while hundreds to thousands of LFEs can occur in under an hour. Here, we investigate how the details of LFE activity can be exploited to estimate the aseismic moment rate of the driving slow slip on hour-long time scales. We use an LFE catalog from the Guerrero subduction zone and calibrate their activity to geodetically-observed slow slip events. We demonstrate that the seismic moment rate of LFEs can be directly related to the moment rate of slow slip, allowing us to turn a catalog of LFEs into a catalog of aseismic slip transients. This result shows that LFE activity is more than just an indicator of when slow slip happens, and is in fact diagnostic of the slow slip that drives LFEs. We then explore how these these hours-long LFE-defined slow transients scale with moment, duration, and recurrence.