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Earthquake cycle simulations for long-term damage evolution and healing in low velocity fault zones
  • Prithvi Thakur,
  • Yihe Huang
Prithvi Thakur
University of Michigan

Corresponding Author:prithvi.thakur93@gmail.com

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Yihe Huang
University of Michigan
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Abstract

Most major strike slip fault systems are surrounded by narrow zones of damaged rocks that can have a crucial effect on earthquake dynamics. Owing to the limited timescale of seismic observations, the structural evolution of this damaged zone and its long-term effects are not well understood. We study the mechanical response of damage evolution and healing over multiple earthquake cycles using fully dynamic earthquake cycle simulations in a 2D vertical strike-slip fault. We use a spectral element method to discretize the domain and a rate-state dependent friction on the fault to simulate all the stages of the seismic cycle, including interseismic slip, earthquake nucleation, rupture propagation and postseismic slip. A narrow, compliant fault-parallel elastic layer with low seismic wave velocities is introduced to emulate near-fault damage. The low-velocity layer reflects waves during the seismic period giving rise to stress heterogeneities that persist through multiple seismic cycles. We introduce a scalar damage multiplier ‘d (01)‘ that reduces the effective shear modulus during the earthquake and increases it during the interseismic period. We study different realizations of d and h through time: the simplest model consists of a constant increase in damage and healing over each seismic cycle and the more complex model includes a heterogeneous damage proportional to the peak slip velocity along the fault. The distribution and evolution of dynamic parameters (shear stresses and slip velocities) and static earthquake parameters (cumulative slip and static stress drops) as a function of the damage is shown and compared to the existing continuum damage rheology models and field geologic observations. These simulations will provide a better insight into the partitioning of damage and healing during seismic cycles and the saturation of damage in mature fault zones.