Rheological heterogeneity on the deep subduction interface: implications for short-term seismic style and long-term subduction dynamics

My talk will focus on what rocks exhumed from deep levels of subduction shear zones tell us about both the short- and long-term mechanical behavior of subduction zones. I will discuss how the rock record suggests that the rheology of the deep interface is strongly dependent on subducted protolith, e.g. ratios of sedimentary to mafic rocks. In terms of short-term mechanical behaviors, I will show how mixtures of sedimentary and mafic protoliths set up an environment of mixed frictional and viscous slip modes that may explain the phenomena of episodic tremor and slow slip. In terms of long-term subduction mechanics, I will discuss how sediment subduction can lead to lubrication of the plate interface and associated increases in subduction plate speeds, which may explain some accelerations and decelerations in subduction rates preserved in the geologic record.