Using a Microphysical Theory of Lithospheric Rock Deformation to Predict Post-Seismic Relaxation

Plate boundaries are where earthquakes commonly occur, and stress evolution in those parts of the lithosphere and upper mantle have dominant effects on the seismic cycle. Earthquake cycles involve periods of fault slip, including fault rupture and release of energy stored in the shallow portions of the plate, and an interseismic period, when the elastic strain is again accumulated before the next earthquake. Deformation across the entire plate boundary shortly after an earthquake influences stress distribution on the fault and is relevant for predicting subsequent seismic events. This study aims to clarify the microphysical mechanisms of post seismic relaxation, to improve stress evolution prediction within tectonic plates and thereby facilitate seismic hazard mitigation. We employ a new microphysical model of rock deformation, which is constrained by rock physics theories, as well as experimental and field studies. This model captures transient rheological properties of deforming rocks, which is essential when investigating an environment where deformation conditions, such as stress and microstructure, evolve relatively quickly. Our modeling results of post-seismic relaxation rates are compared to and constrained by the satellite-based observations and GPS data. Furthermore, our model makes predictions of transient and long-term microstructures in seismically active environments, thereby linking satellite observations of surface motions to observable microstructures of natural rock samples.