Most of the world's seismicity and volcanism occurs along the boundaries of tectonic plates (where they collide, pull apart, or slide past each other). Episodic earthquakes along these boundaries allow the shallower portions of plates to move with respect to each other, but exactly how relative plate motion is accommodated at greater depths is not well understood. Some evidence points to steady, aseismic creep along surfaces separating plates; these surfaces would have to extend from the upper crust to the mantle asthenosphere. Other evidence suggests that continental plate boundaries are not very "plate-like" at all, but that they flow slowly like the mantle, and cannot maintain large deviatoric stresses for long periods of time.

My research is dedicated mainly to numerically modeling plate-boundary deformation over a variety of spatial and temporal scales, to figure out how non-seismically deforming material is distributed along plate boundaries, and what the rheology of this material is. Knowing how this material must distort and flow over time to let one plate move past the other, I can estimate stresses within it and the adjacent plates. This helps place boundaries on the absolute and relative magnitudes of forces that drive plate tectonics. I also use deformation models to calculate the rate at which stress is building up on faults that have not slipped lately, and to evaluate their potential for damaging earthquakes.

I am also interested in using surface displacement data to infer how faults break during earthquakes, in terms of the spatial patterns and magnitudes of slip along the rupture surface. Another (broad) area of interest is modeling how non-tectonic, time-dependent processes in the subsurface (such as magma migration or fluid pressure changes due to oil or water extraction) deform the Earth's surface, and thus how to make inferences about these processes from time-dependent surface deformation patterns.