EAR-PF: Earthquake triggering throughout the seismic cycle: a unified laboratory and seismological study

Vanderelst Nicholas, Santa Cruz CA

Investigators

Abstract

Dr. Nicholas van der Elst has been awarded an NSF Earth Science Postdoctoral Fellowship, to be carried out at Columbia University, to study the physics of earthquake nucleation and triggering. This study will combine observational seismology and laboratory experiments to link earthquake triggering susceptibility to the stress state on the fault. Small earthquakes are commonly initiated by the seismic waves from distant large earthquakes, in what is called remote triggering. Susceptibility to remote triggering varies regionally, and may increase as stresses build throughout the seismic cycle. The purpose of this study is to identify the local conditions that make a fault susceptible to triggering, and to determine whether triggering susceptibility can be used as an indicator of a critical stress state on the fault. The observational component of this study will use seismic waveforms to identify triggered earthquakes near known active faults. This component will capitalize on the recent occurrence of large earthquakes in well-instrumented regions (e.g. off Tohoku, Japan), where we now know that faults were near the end of the seismic cycle. In the laboratory component, simulated gouge-filled faults will be subjected to seismic waves, and acoustic sensors will monitor for changes in triggering susceptibility throughout the stick-slip cycle. This work addresses a major current challenge in the field of earthquake forecasting: how to take the elastic earthquake cycle into account in producing time-varying rupture probabilities. The results will be of use to government agencies tasked with identifying seismic hazard as well as to industries concerned with managing seismic risk. This project will create opportunities to train undergraduate students in digital seismogram processing and experimental rock mechanics.