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Dynamically Triggered Changes in Interface Coupling in Southern Cascadia

Kathryn Materna, Noel M. Bartlow, Aaron Wech, Charles A. Williams, & Roland Bürgmann

Published August 14, 2019, SCEC Contribution #9579, 2019 SCEC Annual Meeting Poster #205

The Mendocino Triple Junction (MTJ) is a rapidly deforming plate boundary zone at the intersection of the San Andreas fault, the Cascadia Subduction Zone (CSZ), and the Mendocino Fault Zone. Earthquake cycle deformation in this region results in large present-day strain rates and seismicity rates. In this project, we analyze GPS time series in the Mendocino region and find systematic velocity changes in the interseismic velocity field between 2010 and 2018. We find that in one area, the GPS velocity field changes in spatially and temporally coherent patterns following large offshore earthquakes. These changes cannot be fully explained by postseismic deformation, slow slip events, or hydrological loading. Instead, we believe that these observations present an example of dynamically triggered changes in interface coupling, including both a coupling increase and a coupling decrease following the occurrence of nearby M>6.5 earthquakes. We test the robustness of these observations to various changes in our methodology. These observations, together with similar examples elsewhere in the world, suggest that faults may experience dynamically triggered changes in coupling during the interseismic period, a phenomenon that we need to better understand and account for in future hazard models.

Materna, K., Bartlow, N. M., Wech, A., Williams, C. A., & Bürgmann, R. (2019, 08). Dynamically Triggered Changes in Interface Coupling in Southern Cascadia. Poster Presentation at 2019 SCEC Annual Meeting.

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Tectonic Geodesy