February 18, 2022 at 10:30am CST
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Host: Shuoshuo Han
Title: The sound of friction: Probing the mechanics of earthquake nucleation through experimental seismology and fault mechanics
Abstract: Variations in seismic wave properties before, during and after frictional instabilities have been documented in laboratory experiments as well as in a limited number of crustal earthquakes. These variations are generally attributed to fault zone healing, changes in crack density, or pore fluid effects modulated dilatation or fault slip. However, the relationships between amplitude and velocity variations during the seismic cycle, and the underlying mechanisms of precursors to failure remain poorly understood. In this talk, I introduce frictional shear experiments and the concurrently measured evolution of seismic wave properties throughout the laboratory seismic cycle. I show, through precise measurements of relative changes in seismic wave properties in the fault zone and surrounding rock, that these waves can probe earthquake nucleation and serve as stress and slip-meters. Moreover, I show that pre-earthquake changes in seismic wave speed may be more common than previously thought because they are masked by far-field tectonic stiffening. These results underscore the importance of continuous and long-term time-lapse monitoring of crustal faults for seismic hazard assessment.