Monitoring Sseismicity Associated With a Possible Asperity on the Cascadia Megathrust

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To study a region of anomalous seismicity along the Cascadia subduction zone, offshore central Oregon, researchers will passively monitor earthquake activity during two, year-long deployments of short-period and broadband ocean bottom seismometers. At least part of the deployment will be concurrent with adjacent onshore deployments that are part of the USArray experiment. The target area has experienced two moderate earthquakes and a swarm of small earthquakes during the past 2 years, and available data suggest that a basement ridge being subducted in this area is hitting the crystalline backstop, possibly causing the deformation detected in the oceanic plate by geodetic experiments. This project will further constrain such deformation. The research also in part represents a test for hypotheses related to the relative strength of forearc and subducting ridge, with different seismicity patterns expected if either of these features is the strong component in the subduction complex. Broader impacts include training of numerous undergraduate and graduate students, establishing baseline data for a possible eventual observatory in this region, and integration with the USArray and Earthscope experiments.