Coulomb stress evolution due to coseismic, postseismic and interseismic deformation in southern California, NE Caribbean and southern Alaska

Syed Tabrez Ali, Purdue University

Abstract

Evolution of Coulomb stress is numerically simulated in three tectonically active regions i.e., Southern California, NE Caribbean and Southern Alaska, in order to better understand the relationship between stress change and earthquake occurrence and to determine where unrelieved stress is currently the greatest. Specifically, all three major phases of the earthquake cycle i.e., interseismic deformation due to tectonic loading, coseismic slip on faults, and subsequent postseismic deformation due to viscous relaxation, are modeled over time scales of known historic seismicity, in order to: (i) estimate stresses that have accumulated on major active faults/fault segments, (ii) explain, possible triggering of historic earthquakes due to stress transfer, and earthquake sequences, and (iii) explain the observed crustal velocities (measured by GPS receivers) while decomposing them into their interseismic and postseismic (transient) components. Calculations demonstrate that large earthquakes always occur on faults that accumulate shear during the interseismic period. Coseismic slip then serves to relieve the accumulated stress on the fault but may increase it on other nearby faults/fault segments, bringing them closer to failure. Subsequent postseismic viscous relaxation serves to reload the fault and can have a large impact on deformation rates and state of stress, both in the near and far field even decades later.

Degree

Ph.D.

Advisors

Freed, Purdue University.

Subject Area

Geophysics

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