Evidence of instantaneous dynamic triggering during the seismic sequence of year 2000 in south Iceland

Abstract

[1] We analyze the coseismic stress perturbation during the 17 June 2000 south Iceland seismic sequence; the main shock (M s 6.6) was followed by three large events within a few tens of seconds (8, 26, and 30 s) located within 80 km. The aim of this paper is to investigate short-term fault interaction and instantaneous triggering. This happens when a fault perturbed by a stress change fails before the end of the transient stress perturbation. We compute the shear, normal, and Coulomb stress changes as functions of time in a stratified elastic half-space by using discrete wave number and reflectivity methods. We calculate dynamic stresses caused by the main shock at the hypocenters of these three subsequent events. Our numerical results show that the onset of the last two events is slightly delayed with respect to the arrival time of the second positive peak of Coulomb stress variation, while the first event occurred after the first positive stress peak. We have also analyzed the response of a spring slider system representing a fault governed by a rate-and state-dependent friction law, perturbed by shear and normal stress variations caused by the main shock. The fault response to the computed stress perturbations is always clock advanced. We have found suitable constitutive parameters of the modeled fault that allow the instantaneous dynamic triggering of these three earthquakes. If the initial sliding velocity is comparable with the tectonic loading velocity, we obtained failure times close to the observed origin times for low values of the initial effective normal stress.

Effect of frictional heating and thermal advection on pre-seismic sliding: a numerical simulation using a rate-, state- and temperature-dependent friction law

“…In agreement with recent studies (Belardinelli et al, 2003;Rubin and Ampuero, 2005;Antonioli et al, 2006) we assume V = 0.1 m s −1 as the limit value for the occurrence of instability.…”

A thermal pressurization model for the spontaneous dynamic rupture propagation on a three‐dimensional fault: 1. Methodological approach

“…Fluids can affect the earthquake nucleation process: high fluid pressure can allow fault reactivation with the inversion of slip direction (such as low angle thrust fault reactivated by normal faulting [see Sibson , 1986; Collettini et al , 2005, and references therein]). They can also trigger aftershocks controlling the patterns of seismicity both in space and time [e.g., Nur and Booker , 1972; Miller et al , 1996, 2004; Yamashita , 1998; Shapiro et al , 2003; Antonioli et al , 2006]. Fluid flow and pore pressure evolution can also affect the dynamic propagation of earthquake ruptures: frictional heating caused by earthquake dislocation can modify the pore pressure and therefore the effective normal stress acting on the fault surface.…”

Seismicity in a model governed by competing frictional weakening and healing mechanisms

“…Observational evidence relates fluids to a variety of faulting phenomena, such as fluid driven aftershocks (Nur & Booker 1972;Bosl & Nur 2002;Miller et al 2004;Piombo et al 2005), remotely triggered earthquakes (Hill et al 1993;Husen et al 2004;Antonioli et al 2006), generation of aseismic transients, tremors and possibly silent slip events (Segall & Rice 1995;Shibazaki 2005;Liu & Rice 2007). Laboratory experiments investigate the mechanisms responsible for overpressured fluid states (Sleep & Blanpied 1992;Lockner & Byerlee 1994;Blanpied et al 1998), and highlight the essential role of fluid phases associated with healing and restrengthening (Nakatani & Scholz 2004;Tenthorey & Cox 2006).…”