Aseismic slip dynamics at the down-dip edge of seismogenic zones: insights from the Parkfiled segment of the San Andreas Fault and the Alaska subduction zone

Baptiste Rousset, UC Berkeley

Wednesday, May 8, 2019 at 10:30 AM

Location:
Building 3, Rambo Auditorium
Host:
Belle Philibosian

At the down-dip edge of some subduction seismogenic zones, slow slip events (SSE) have been discovered with
continuous GPS measurements. When accompanied by low amplitude seismic signals called tremors, the combined
phenomenon is named episodic tremor and slip (ETS). In some places, episodic tremors are observed without clear
signal on the geodetic time series. In this presentation, I show that we can use the timing of tremor signals to extract
a geodetic signature of ETS in the case of the San Andreas Fault (SAF) and the Alaska subduction zone. On the
Parkfield segment of the SAF, we extract an average Mw 4.9 SSE localized at about 18 km depth, at the transition
between the creeping section of the SAF and the Parkfield locked asperity. In Alaska, we show that the five year-
long upper cook inlet SSE described as a smooth slip event in time by previous studies, is in reality a cluster of
short term SSEs colocalized with tremor bursts. In both contexts, these observations shed light on the slip dynamics
during the interseismic phase of the seismic cycle and help understand the seismogenic zones loading processes.

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