EAR PF: Investigating the competition between thermal pressurization and dilatancy on rough surfaces at earthquake slip rates

Barbery, Monica R, College Station TX

Investigators

Abstract

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2). An NSF EAR Postdoctoral Fellowship has been awarded to Dr. Monica Barbery to investigate earthquake physics at Brown University under the mentorship of Dr. Terry Tullis. Dr. Barbery will work to understand how rocks behave when exposed to the friction produced when there is rapid movement on a fault. The postdoctoral fellow will use new experimental machinery to conduct the first rock friction experiments at the velocity and pressures of real earthquakes to understand earthquake processes and the associated risks. This work will improve the ability to scale existing laboratory results to nature. This research will help in the development and modification of new and existing earthquake models that play a vital role in mitigating earthquake risk. In addition to these research activities, Dr. Barbery will work with Providence public schools to develop and implement curriculum for an educational outreach program at Brown University and will co-teach a stacked graduate and undergraduate course within the Department of Earth, Environmental, and Planetary Sciences. Dynamic weakening by thermal pore fluid pressurization (TP) and dynamic strengthening by dilatancy hardening (DH) are mechanisms theorized to contribute to the frictional strength and stability of faults during earthquakes. TP occurs as frictionally heated pore fluids expand along undrained faults to frictionally weaken the fault. DH occurs as microcracks develop during shearing and as previously mated fault surfaces become unmated with slip, both of which increase pore space and frictionally strengthen the fault. Both processes are closely tied to the roughness and displacement history of the sliding surface however TP will only contribute significantly to the frictional weakening that leads to earthquake instability if DH is minimal. Rock friction experiments will be conducted to examine the efficacy of TP and DH at elevated slip rates (≥100 mm/s), elevated confining pressure (≥25 MPa), and elevated pore pressure (≥25 MPa) using a newly modified rotary shear apparatus. Experiment results will be combined with modelling to characterize the competition between TP and DH across a range of slip rate, roughness, and displacement scales to better understand how to scale DH and TP processes to earthquakes on natural 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.