CAREER: Experimental investigation of deformation and slip behaviors of subduction megathrust rocks

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Devastating earthquakes and tsunamis recur in subduction zones, and the time interval between large earthquake events ranges from decades and centuries. Long-lasting international collaborative research and education programs are necessary to advance understanding of earthquake source physics and transfer the knowledge from the past events to future generations. To advance understanding of deformation and slip behaviors of megathrust plate boundary faults and physics of earthquakes in subduction zones, this project involves development of innovative deformation and friction experiments on natural fault rocks at elevated pressure and temperature conditions that are anticipated along the plate boundary faults. To expand students' learning opportunities on experimental rock deformation and subduction zone earthquake and tsunami hazards, the principal investigator develops new education programs including a senior capstone course, a training course for graduate students and early-career scientists in geoscience and engineering, and an international field trip that will educate students on subduction zone earthquakes and tsunamis and hazard mitigation for natural disasters. The education programs are designed to provide hands-on laboratory experience in rock deformation and insights into subduction zone earthquakes. Trough these programs, next-generation researchers will be trained to facilitate interdisciplinary and international collaborations on tectonic, geodynamic, and engineering problems and to advance the transfer of discovery and natural hazard mitigation to future generations. Development of elevated pore fluid pressure along the megathrust plate boundary faults and thus low strength of faults are inferred from many geophysical and geological observations including low seismic velocity, high reflectivity taper angle of the accretionary prism wedge, and vein formation. This project will test the hypothesis that deformation and slip behaviors at low effective stress may control a spectrum of slip events and earthquakes observed along the megathrust plate boundary faults. A series of true-triaxial compression tests, conventional triaxial extension tests, and triaxial friction experiments under controlled pore pressure will be conducted on natural megathrust fault rocks. Low effective pressure at a range of loading paths and rates will be achieved by controlling of magnitude and pressurization rates of pore pressure. The series of experiments will document the effects of elevated pore pressure and loading paths and rates on the formation of shear, extensional, and hybrid extension-shear fracture and frictional behaviors, and thus can provide mechanical perspectives on vein formation associated with slip along the plate boundary faults.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.