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Coupling long-term and short-term physics of an earthquake on complex fault
  • Khurram Aslam
Khurram Aslam
University of Memphis

Corresponding Author:ksaslam@memphis.edu

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We couple short-term (i.e. the co-seismic) and long-term (i.e. the inter-seismic) phase of an earthquake, in order to investigate how induced static stress changes during the co-seismic phase of an earthquake cycle influence the dynamics of strain accumulation during the inter-seismic phase. We perform dynamic rupture simulations on complex strike slip faults in 2D, incorporating off-fault plastic failure and strong dynamic weakening on the fault governed by the slip weakening law. Our strike slip fault has a self-similar fractal profile with RMS height taken from observational studies. Our dynamic rupture simulation results show that the stresses in the region surrounding the fault are highly complex and heterogeneous. This heterogeneity in stresses is mainly related to roughness of fault profile and at distances where fault roughness effects are not dominant, the stresses are mostly uniform. We extract these complex stresses together with the plastic deformation from the dynamic model and use them as the input to run the long-term tectonic model (LTM). This provides us insight into the dynamics of off-fault plastic deformation in the loading phase of an earthquake. Our LTM results show that most of the shear zones (i.e. new features e.g. fractures and faults) develop and grow at oblique angles to the main fault while considerable amount of damage keeps accumulating along the immediate sides of the fault profile. The development and growth of these new features occurs in the locations where geometrical bends in the fault profile has caused the deformation in the dynamic phase to be localized. This localized deformation due to fault roughness acts as a seed for the development of new features. We conclude that the complex damage pattern in the fault damage zones (observed in observational studies) is mainly due to the fault surface roughness effects. During the co-seismic phase, the stresses concentrate near the fault bends due to rough fault profile. During the inter-seismic phase, these locations are favored for the development of new features during the inter-seismic phase the earthquake.