Séminaire ISTeP - Baptiste Rousset

(Univ. Berkeley)

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

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.

22/03/2019, Salle Fourcade à 12h30