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Published December 2012 | Published
Journal Article Open

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


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 (ψ = 45◦) to the maximum compressive background stress. The simulations and analytical scaling results show that for crack-like ruptures (1) the maximum yielding zone thickness T_(max) 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 ε^p_0 decays logarithmically with fault normal distance at a rate depending on the stress state and S; (3) increasing rock cohesion reduces T_(max)/L, resulting in faster rupture speed and higher inclination angle Ф 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 ψ = 45◦, 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 ψ = 10◦, representative for thrust faulting, the energy dissipation to yielding leads to opposite preferred rupture propagation. In all cases, Ф is higher on average on the compliant side. For both crack and pulse ruptures with ψ = 45◦, T decreases and ε^p_0 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.

Additional Information

© 2012 The Authors. Geophysical Journal International © 2012 RAS. Accepted 2012 September 19. Received 2012 July 4; in original form 2012 February 8. Article first published online: 26 Oct. 2012. We thank Massimo Cocco, an anonymous referee and Editor Xiaofei Chen for useful comments. The study was supported by the National Science Foundation (grants EAR-0944066 and EAR-0908903) and the Southern California Earthquake Center (based on NSF Cooperative Agreement EAR-0529922 and USGS Cooperative Agreement 07HQAC0026).

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