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

Abstract

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 () 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 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 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.

Off-fault long-term damage: A condition to account for generic, triangular earthquake slip profiles

“…We prescribe a preexisting damage zone with a rectangular shape around the slip plane and with homogeneous elastic properties (Figure 2b). This case is that prescribed in most available theoretical models, which consider that predamage is uniform along the fault [Andrews, 2005;Ma, 2008;Templeton and Rice, 2008;Dunham and Rice, 2008;Ma and Andrews, 2010;Kaneko and Fialko, 2011;Huang and Ampuero, 2011;Xu et al, 2012b;Gabriel et al, 2013]. We impose the damage zone to have different widths (W) ranging from 3 to 50% of the fault length.…”

“…Field observations of long-term faults and related damage Cowie, 2001, 2003;Kim et al, 2004;Manighetti et al, 2004;Dor et al, 2006;Faulkner et al, 2011] (Figure 1b), as well as dynamic simulations of coseismic damage [e.g., Andrews, 2005;Templeton and Rice, 2008;Viesca et al, 2008;Dunham et al, 2011aDunham et al, , 2011bXu et al, 2012aXu et al, , 2012bXu and Ben-Zion, 2013], suggest that damage zones around faults and ruptures commonly have an overall triangular shape in map view, with an apex centered in the zone of fault or rupture initiation, and a damage zone widening in the direction of fault or earthquake propagation ( Figure 1b). Here we test the effect of an overall triangular-shaped preexisting damage zone of the form sketched in Figures 1b and 2c.…”

“…An increasing number of observations support this suggestion, in which significant coseismic failure and strain occurs around large earthquake ruptures [Fialko et al, 2002;Fialko, 2004;Hamiel and Fialko, 2007;Cochran et al, 2009;Fielding et al, 2009]. Experimental and theoretical models have also been developed recently to examine whether off-fault coseismic damage could emerge from the dynamic rupture process [Harris and Day, 1997;Lyakhovsky et al, 1997;Yamashita, 2000;Poliakov et al, 2002;Dalguer et al, 2003;Rice et al, 2005;Andrews, 2005; Ben-Zion and Shi, 2005;Ando and Yamashita, 2007;Bhat et al, 2007;Templeton and Rice, 2008;Biegel et al, 2008;Viesca et al, 2008;Dunham and Rice, 2008;Duan and Day, 2008;Ma, 2008;Sammis et al, 2009;Dieterich and Smith, 2009;Finzi et al, 2009;Bhat et al, 2010;Biegel et al, 2010;Ma and Andrews, 2010;Shi et al, 2010;Hok et al, 2010;Savage and Cooke, 2010;Dunham et al, 2011aDunham et al, , 2011bXu et al, 2012aXu et al, , 2012bNgo et al, 2012;Suzuki, 2012;Xu and Ben-Zion, 2013;Gabriel et al, 2013]. Although they are based on different formalisms, all these models confirm that significant coseismic off-fault damage does develop during the earthquake rupture, with this ...…”

“…Therefore, natural earthquakes rupture faults that are embedded in a predamaged medium, with this long-term damage having properties that vary both across and along the fault. Most available theoretical models take into account the predamaged state, yet consider that predamage is uniform along the fault [Andrews, 2005;Ma, 2008;Templeton and Rice, 2008;Ma and Andrews, 2010;Kaneko and Fialko, 2011;Huang and Ampuero, 2011;Xu et al, 2012b;Gabriel et al, 2013], at best varying across the fault [Harris and Day, 1997;Ben-Zion and Huang, 2002;Ben-Zion and Shi, 2005;Rudnicki and Rice, 2006;Ampuero and Ben-Zion, 2008;Dunham and Rice, 2008]. We suspect that this simplification might be one of the reasons of the discrepancy between model results and natural earthquake slip profiles.…”

Recent advances in imaging crustal fault zones: a review

“…Therefore, the LVZ structure may reflect the behavior of past ruptures (e.g., Dor et al 2006;Ben-Zion and Ampuero 2009;Xu et al 2012). Furthermore, the LVZ can exert significant influence on properties of future ruptures based on results of numerical experiments (e.g., Harris and Day 1997;Huang and Ampuero 2011;Huang et al 2014).…”