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Geodetic Coupling Models as Constraints on Stochastic Earthquake Ruptures: An Example Application to PTHA in Cascadia
  • David T Small,
  • Diego Melgar
David T Small
University of Oregon

Corresponding Author:dsmall2@uoregon.edu

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Diego Melgar
University of Oregon
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Current stochastic rupture modeling techniques do not consider the influence of first order fault zone characteristics. One such key characteristic is fault slip deficit or inter-seismic locking which has shown correlation between areas of high coupling and areas of greater slip in many recent large ruptures globally. Therefore, it is reasonable to assume that it should be considered as prior information in rupture modeling. Here, we first present a mathematical formalism to introduce locking models as prior information into stochastic rupture modeling. We then focus on how introducing slip deficit information into the stochastic rupture models influences slip distributions for the Cascadia Subduction Zone (CSZ). We compare rupture models created with two end member models of locking, one with a fully locked zone extending to the trench and another with locking deeper downdip, along with models created without a prior knowledge of locking. Large variations occur and correlate well with areas with the largest differences in slip deficit. To exemplify their impacts, the ruptures are then used for probabilistic tsunami hazard assessment. We find that overall the tsunami amplitudes generated are much more hazardous in the northern extent of the CSZ where differences in locking distribution are more prevalent. Although large uncertainties are present in accuracy of locking, imposing either constraint created very different hazard estimations when compared to the hazards where no prior locking information was used. This highlights the necessity to expand seafloor instrumentation and to consider first order fault information like locking in future authoritative hazard assessments.
Jul 2021Published in Journal of Geophysical Research: Solid Earth volume 126 issue 7. 10.1029/2020JB021149