Locking Degree for the Chilean Subduction Zone Inferred Through Bayesian Inversion of GPS Observations and Its Mechanical Link to Seismicity

Date: 4/25/2019

Time: 06:00 PM

Room: Grand Ballroom

Kinematic models suggest that the lateral extents and magnitudes of earthquake ruptures are fundamentally controlled by the spatial distribution of locking degree, which can be used to infer variations of stress build-up along the seismogenic zone. However, estimates of locking degree rely on the wealth of the geodetic data, modeling assumptions and inversion technique, and therefore maps of locking even for same areas that use similar data are very distinct. Here, we build a spherical Finite-Element model of the Chilean Subduction Zone to generate Green Functions of back slip that takes into account the viscoelastic interseismic response. We use a Bayesian method based on the reversible jump algorithm for the inversion of a compilation of more than 500 interseismic GPS velocities along the Chilean margin. We apply this method to solve for the back slip at the plate interface and for the rotation parameters of a continental-scale forearc sliver block. We further investigate the relation between interseismic background seismicity and locking degree at different segments of the Chilean margin, aiming to describe the current stage of stress build-up within the seismic cycle. Seismicity spatial patterns surrounds the deeper regions of the locked patches, indicating a mechanical link between stress build-up and deeper seismogenic zone seismicity. Together, our study robustly characterizes the locking degree along the Chilean seismogenic zone and provides valuable insights for understanding the stress accumulation-and-release processes that lead to great megathrust earthquakes, and allow estimates of the current seismic potential of locked segments.

Presenting Author: Marcos Moreno

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