Title: Microphysics of creep at tectonic plate boundaries

Abstract: Plate tectonics governs almost all geological activity at Earth’s surface. Tectonic plate boundaries are the locus of geological hazards such as earthquakes and volcanoes. The processes through which the plates form and evolve entails the microscale physics of lithospheric deformation. Specifically, the strength of the lithosphere is controlled by the formation and motion of crystalline defects in rock-forming minerals, such as dislocations and grain boundaries. My current work focuses on two leading-order issues in lithospheric deformation at tectonic plate boundaries: (1) Strength of the lithosphere on human versus geological time scales: When rocks deform slowly, such as over the timescale of millions of years for mantle flow, their creep mechanisms and thus strength are different from when they deform fast, such as during earthquakes or in laboratory experiments. Furthermore, after deforming for millions of years, plate boundaries acquire a unique microstructural imprint reflective of their deformation history, which has a first-order effect on their strength today, including their response to seismic and magmatic activity. (2) Transient creep properties of the lithosphere in response to stress changes: When stress in the lithosphere changes, for example during earthquake cycles, rock microstructure and thus strength take time to adjust. The resulting time-lag between stress changes and mechanical equilibration makes the lithosphere weaker or stronger during the transient stages. In this talk, I will present microphysical models of microstructural evolution and transient creep properties that help us understand the geodynamics of both slowly and rapidly changing tectonic environments.

About the Series: Seminar in Geophysics 12.571 is a class for MIT EAPS graduate students covering current topics in geophysics. Anyone from the MIT community is welcome to join for the talks by guest speakers which take place approximately every two weeks, usually on Tuesdays at 10am in 54-915 and on Zoom. Titles and abstracts will be posted here when available.