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Properties of Inelastic Yielding Zones Generated by In-plane Dynamic Ruptures: II. Detailed parameter-space study

Shiqing Xu, Yehuda Ben-Zion, & Jean-Paul Ampuero

Published December 2012, SCEC Contribution #1706

We perform a detailed parameter-space study on properties of yielding zones generated by 2D in-plane dynamic ruptures on a planar fault with different frictional 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 ( ) to the maximum compressive background stress. The simulations and analytical scaling results show that for crack-like ruptures (1) the maximum yielding zone thickness linearly increases with rupture distance L and the ratio is inversely proportional to with S being the relative strength parameter; (2) the potency density decays logarithmically with fault normal distance at a rate depending on the stress state and S; (3) increasing rock cohesion reduces , resulting in faster rupture speed and higher inclination angle 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 , 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 , representative for thrust faulting, the energy dissipation to yielding leads to opposite preferred rupture propagation. In all cases, is higher on average on the compliant side. For both crack and pulse ruptures with , T decreases and 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.

Xu, S., Ben-Zion, Y., & Ampuero, J. (2012). Properties of Inelastic Yielding Zones Generated by In-plane Dynamic Ruptures: II. Detailed parameter-space study. Geophysical Journal International, 191(3), 1343–1360. doi: 10.1111/j.1365-246X.2012.05679.x.