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Effect of fault roughness on aftershock distribution and post co-seismic strain accumulation
  • Khurram Aslam
Khurram Aslam
University of Memphis

Corresponding Author:[email protected]

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We perform physics-based simulations of earthquake rupture propagation on geometrically complex strike-slip faults. We consider many different realization of the fault roughness and obtain heterogeneous stress fields by performing dynamic rupture simulation of large earthquakes. We calculate the Coulomb failure function (CFF) for all these realizations so that we can quantify zones of stress increase/shadows surrounding the main fault and compare our results to seismic catalogs. To do this comparison, we use relocated earthquake catalogs from Northern and Southern California. We specify the range of fault roughness parameters based on past observational studies. The Hurst exponent (H) varies in range from 0.5 to 1 and RMS height to wavelength ratio ( RMS deviation of a fault profile from planarity) has values between 10-2 to 10-3. For any realization of fault roughness, the Probability density function (PDF) values relative to the mean CFF change show a wider spread near the fault and this spread squeezes into a narrow band as we move away from fault. For lower value of RMS ratio ( 10-3), we see bigger zones of stress change near the hypocenter and for higher value of RMS ratio ( 10-2), we see alternate zones of stress increase/decrease surrounding the fault to have comparable lengths. We also couple short-term dynamic rupture simulation with long-term tectonic modelling. We do this by giving the stress output from one of the dynamic rupture simulation (of a single realization of fault roughness) to long term tectonic model (LTM) as initial condition and then run LTM over duration of seismic cycle. This short term and long term coupling enables us to understand how heterogeneous stresses due to fault geometry influence the dynamics of strain accumulation in the post-seismic and inter-seismic phase of seismic cycle.