Geodynamics and earthquakes of subduction zones

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The proposed research is designed to understand mechanical processes of subduction zones. The findings will have important implications for understanding the geodynamics of plate subduction, especially its earthquake processes. This proposal seeks limited funding to provide partial support for two graduate students at any given year over the next five years to conduct computer modeling on three subjects. The first subject is the deformation cycles of great subduction earthquakes such as the M 9 earthquake in 1700 off Canada's west coast. Based on geodetic and seismological observations from different subduction zones, we will develop models to address how the Earth's crust and mantle deform during and after an earthquake and how strain energy is re-accumulated leading to the next event. The second subject is the Episodic Tremor and Slip (ETS), a phenomenon newly found downdip of the seismogenic zone of some subduction faults, such as at the Cascadia subduction zone off the west coast. This will help us understand the complex behavior of subduction faults, that is, why and how they slip not only in earthquakes but also in aseismic slip transients during the time between earthquakes. The third subject is geometrical and structural controls on great subduction earthquakes. Earthquake rupture is a manifestation of unstable friction, but subduction faults are not discrete frictional contacts but zones of three-dimensional structural complexity. We will work on a new conceptual framework that will allow us to address many unanswered first-order questions such as why the Cascadia subduction zone tends to produce infrequent but giant (M ~ 9) earthquakes while many other subduction zones tend to produce more frequent but smaller events.