The collective behavior of deep fault asperities during non-volcanic tremor and slow slip

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This project explores a recently discovered geophysical phenomenon, non-volcanic tremor, whose physical origins are not yet known. This multi-component project combines theory, observations and experiments in a synergistic way, and gathers a team with expertise in several areas: observational seismology, computational modeling and experimental fracture mechanics. The project will provide new observations, employing data from two distinct regions and from laboratory experiments. Whereas the related phenomenon of episodic slow slip transients has been previously addressed by models and experiments, analog and computational modeling of non-volcanic tremor is only incipient. The proposed research aims at filling that gap while contributing with innovative methodologies in large dataset analysis, multi-scale computational modelling and combined optical and acoustic techniques for imaging fracture. The proposed studies concern regions of the United States and South America that are highly exposed to earthquake hazard. Understanding the relations between non-vocanic remor and mechanics of seismogenic zones, a question addressed by this proposal, can provide important input for earthquake hazard assessment. If NVT activity proves to be a natural creepmeter it will provide a means to remotely monitor the small aseismic slip transients related to the nucleation of large earthquakes. The project will provide new targets for field experiments to study NVT. It will enhance and diversify the expertise of two post-doctoral fellows and will provide training for a graduate student.This project consists of three components: (1) an observational component proposing a systematic search for NVT in seismic waveform datasets from Southern California and from the Peru-Chile subduction zone; (2) a theoretical and computational component involving the development of a multi-scale modelling approach and studies of the collective behavior of asperities during tremor and slow slip in rate- and- state models and their response to transient and periodic stresses; and (3) an experimental component that will address the effect of transient and periodic loads on the response of fault asperities.