Earthquake triggering by static and dynamic stress changes

Abstract

[1] In this study we aim to understand the effect of static and dynamic stress changes in promoting earthquake failures on secondary faults. Toward this goal we solve the equation of motion of a spring-slider dynamic system including inertia and using rate-and state-dependent constitutive laws. We separately investigate the dynamic response of this fault analog system to a sudden stress change represented either as a stress step or as a stress pulse, which are used to model permanent (static) and transient (dynamic) stress perturbations. The induced earthquake failure does not occur immediately at the application of the coseismic stress change, but it is delayed in time: we define this time interval as the triggering delay. For a given stress perturbation, we analyze the dependence of triggering delays on different system conditions and constitutive parameters. Our results clearly show that the effects of static and dynamic stress changes are quite different. While a static stress change is able to advance as well as to delay an induced instability depending on its sign, a dynamic stress pulse is only able to promote a nearly instantaneous failure, provided its amplitude is positive and large enough with respect to the direct effect of friction. In other words, dynamic stress changes can only cause nearly instantaneous failures, without any relevant triggering delay. These results should be considered in interpreting the seismicity rate changes caused by large earthquakes at least as long as seismic events are interpreted as sliding instabilities obeying rate-and state-dependent friction laws.INDEX TERMS: 7209 Seismology: Earthquake dynamics and mechanics; 7260 Seismology: Theory and modeling; 7299 Seismology: General or miscellaneous; KEYWORDS: stress trigger, fault interaction, rate-and state-dependent friction, spring-slider Citation: Belardinelli, M. E., A. Bizzarri, and M. Cocco, Earthquake triggering by static and dynamic stress changes,

Coulomb stresses imparted by the 25 March 2007 Mw=6.6 Noto-Hanto, Japan, earthquake explain its ‘butterfly’ distribution of aftershocks and suggest a heightened seismic hazard

“…Rather, it may have raised the likelihood of shaking by promoting failure on adjacent thrust faults. Although we can not estimate the time dependency of the stress increase effect on the faults, it is possible that any transient triggering effect on the nucleation process would be diluted rapidly (Dieterich, 1994); however, such a process could last several years to several decades based on the results of previous studies (e.g., Toda and Stein, 2003). Such a hypothesis can be partially validated from the fact that aftershocks associated with the 1993 M = 6.6 Noto-Hanto-oki earthquake are still visible (Fig.…”

“…The former concept is often explained by the rate-and state-dependent constitutive formulation of earthquake occurrence given by Dieterich (1994) together with Coulomb stress steps (e.g., Stein et al, 1997). Figure 6 in Dieterich (1994) elucidates how the expansion of aftershock zones is controlled by the stress change normalized by Aσ (a constitutive parameter A × the effective normal stress σ ). To reproduce the rapid aftershock expansion seen in the Noto Hanto sequence, Aσ should be quite small.…”

“…where μ is the apparent friction, which includes the effect of the pore pressure change associated with the normal stress change (Cocco and Rice, 2003). We compute the Coulomb stress change in an elastic half-space (Okada, 1992) under the assumption that a shear modulus of 3.2 × 10 11 dyn cm −2 and a Poisson's ratio of 0.25.…”

Earthquake Recurrence in Simulated Fault Systems

“…Laboratory studies of earthquake nucleation processes (DIETERICH and KILGORE, 1996) and studies of earthquake nucleation with rate-and state-dependent constitutive properties (DIETERICH, 1992(DIETERICH, , 1994RUBIN and AMPUERO, 2005) indicate that nucleation processes are highly time-and stressdependent. Seismicity models that incorporate nucleation with rate-and state-dependent friction reproduce a variety of characteristics observed in seismicity data including foreshocks and aftershocks with Omori-type temporal clustering (DIETERICH, 1987(DIETERICH, , 2007GOMBERG et al, 1997GOMBERG et al, , 1998GOMBERG et al, , 2000BELARDINELLI et al, 2003;ZIV and RUBIN, 2003).…”

Conditions for the occurrence of seismic sequences in a fault system

“…Fault interaction and its role in earthquake triggering have been widely studied (e.g. Stein et al, 1992;Harris, 1998;Stein, 1999;Gomberg et al, 2000;Belardinelli et al, 2003;Steacy et al, 2005). Whenever a fault slips, it transfers stress to neighbouring faults, thus anticipating the instant of time when they slip in their turn.…”