Collaborative Research: Resolving Structural Control of Episodic Tremor and Slip Along the Length of Cascadia

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A deployment of broadband and short period seismic instruments from Earthscope's Flexible Array is being used to study segmentation along the length of the Cascadia subduction zone. The experiment is designed to examine the potential links between episodic tremor and slip and the three-dimensional structure of the overriding plate including differences in the geologic terranes and features associated with seismogenic behavior. The Flexible Array deployment complements existing seismic stations from the Transportable Array and permanent networks to provide a uniformly dense network with a typical station spacing of 40 km. Station coverage extends from northern California, through Oregon, to the northern border of Washington, from the coast to the eastern side of the volcanic arc. This dense seismic station coverage, combined with enhanced GPS instrumentation from the Plate Boundary Observatory, is being used to investigate spatial and temporal patterns of non-volcanic tremor and slow slip episodes throughout the entire Cascadia subduction zone. Preliminary work reveals segmentation in the characteristics of episodic tremor and slip which do not appear to correlate with the subducting plate. Seismic imaging of the overriding continental plate will provide the necessary structural control to investigate potential relationships with along-strike variations in geology and rheology of the upper plate.