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Properties of inelastic yielding zones generated by in-plane dynamic ruptures—II. Detailed parameter-space study

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SUMMARY

We perform a detailed parameter-space study on properties of yielding zones generated by 2-D in-plane dynamic ruptures on a planar fault with different friction laws and parameters, different initial stress conditions, different rock cohesion values, and different contrasts of elasticity and mass density across the fault. The focus is on cases corresponding to large strike-slip faults having high angle (inline image) to the maximum compressive background stress. The simulations and analytical scaling results show that for crack-like ruptures (1) the maximum yielding zone thickness Tmax linearly increases with rupture distance L and the ratio Tmax/L is inversely proportional to (1 +S)2 with S being the relative strength parameter; (2) the potency density inline image decays logarithmically with fault normal distance at a rate depending on the stress state and S; (3) increasing rock cohesion reduces Tmax/L, resulting in faster rupture speed and higher inclination angle inline image of expected microfractures on the extensional side of the fault. For slip pulses in quasi-steady state, T is approximately constant along strike with local values correlating with the maximum slip velocity (or final slip) at a location. For a bimaterial interface with inline image, the energy dissipation to yielding contributes to developing macroscopically asymmetric rupture (at the scale of rupture length) with the same preferred propagation direction predicted for purely elastic cases with Coulomb friction. When inline image, representative for thrust faulting, the energy dissipation to yielding leads to opposite preferred rupture propagation. In all cases, inline image is higher on average on the compliant side. For both crack and pulse ruptures with inline image, T decreases and inline image increases for conditions representing greater depth. Significant damage asymmetry of the type observed across several large strike-slip faults likely implies persistent macroscopic rupture asymmetry (unilateral cracks, unilateral pulses or asymmetric bilateral pulses). The results on various features of yielding zones expected from this and other studies are summarized in a table along with observations from the field and laboratory experiments.

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