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Distinguishing slip from the M6.4 and M7.1 Ridgecrest earthquakes using campaign GPS and InSAR data
  • Gareth Funning,
  • Michael Floyd,
  • Rachel Terry
Gareth Funning
University of California Riverside

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Michael Floyd
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Rachel Terry
University of California Riverside
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The 2019 Ridgecrest earthquakes pose interesting questions about the nature of intersecting conjugate ruptures, and also the possibility of re-rupture of fault segments. Aftershocks of the July 4th M6.4 event suggest the possibility of a secondary rupture along the fault that subsequently ruptured in the July 5th M7.1 event. Unfortunately, neither InSAR nor rupture mapping will be able to resolve this question, as no SAR acquisitions were made between the two earthquakes, and the critical ‘nexus’ of the two ruptures was located on the China Lake Navy base, and was not accessible between the events. Campaign GPS data and seismic data may provide clues to resolving these questions. We reoccupied 5 previously surveyed GPS benchmarks in the hours following the M6.4 event, meaning that we can separately measure the deformation from the two earthquakes at those locations. We construct a joint inversion of our campaign GPS data, along with the daily displacements of nearby continuous GPS stations, and ascending and descending Sentinel-1 InSAR data, in order to separate the fault geometry and slip of the two earthquakes, and address the question of re-rupture. This approach also allows us to precisely estimate the contribution of the early postseismic deformation to the InSAR data.