Physical Society Colloquium

Slow slip events along plate boundary fault

Yajing Liu

Earth and Planetary Science
McGill University

The discovery of episodic slow slip events (SSE), sometimes accompanied by low-frequency seismic tremors, along major plate boundary faults has revolutionized our understanding of the spectrum of fault slip in an earthquake cycle. SSEs involve a few mm to cm of displacement released over a few days to months updip or downdip of the seismogenic zone, and some exhibit quasi-periodic recurrence intervals of several months to years. In this talk, I will first discuss numerical modeling effort, in the framework of rate-state friction, to understand the physical mechanism of SSEs and their relationship to subduction zone earthquakes, with a focus on the Cascadia margin. Episodic SSEs emerge spontaneously around friction stability transitional depths where pore pressure is near-lithostatic. SSE recurrence interval is largely controlled by the level of effective normal stress, and subduction fault geometry strongly influences along-strike slip segmentation. I will also present work on slow slip events in the context of continental and oceanic transform faults. In particular, using ocean bottom seismic observation and numerical modeling of earthquake sequences on the Gofar Transform Fault of East Pacific Rise, we found that strong dilatancy effect can stabilize seismic rupture propagation and result in rupture barriers where aseismic slip transients arise episodically. These aseismic/slow slip events may serve as a driving force for the abundant microseismicity detected on Gofar.