A new finite element model in studying earthquake triggering and continuous evolution of stress field

Abstract

A new finite element model in studying earthquake triggering and continuous evolution of stress field.In this paper, a new finite element model (FEM) in consideration of regional stress field and an earthquake triggering factor C are proposed for studying earthquake triggering and stress field evolution in an earthquake sequence. The factor C is defined as a ratio between the shear stress and the frictional strength on a slip surface, and it can be used to tell if earthquake is triggered or not. The new FEM and the factor C are used to study the aftershock triggering of the 1976 Tangshan earthquake sequence. The results indicate that the effects of the stress field and the heterogeneity of the Tangshan earthquake fault zone on the aftershock triggering are very important. The aftershocks fallen in the earthquake triggering regions predicted by the new FEM are more than those fallen in the regions of ΔCFS≥ 0 predicted by seismic dislocation theory. new finite element model, earthquake triggering factor, regional stress field, earthquake sequence Aftershock triggering of a large earthquake is a very interesting problem. Smith et al. [1] calculated the strain energy changes induced by the larger earthquakes in southern California since 1812 and showed that the probability of the larger earthquake occurrence would be reduced at least temporarily in the region where the storied strain energy significantly decreased. Based on dislocation theory, Rybicki [2] and Yamashina [3] attributed the aftershock triggering to the increase of shear stress or shear strain. Das and Scholz [4] studied four large earthquakes and found that the areas of the shear stress increase are consistent with those of the aftershock triggering. Stein and Lisowski [5] first proposed the concept of Coulomb stress change (ΔCFS=Δτ n

A Study of the Impact of Static Coulomb Stress Changes of Megathrust Earthquakes Along Subduction Zone on the Following Aftershocks

“…In fact, ∆CFS> 0 only means the probability increase of the earthquake occurrence. The earthquake occurrence is related not only to ∆CFS but also to the stresses before the mainshock [51] . On the one hand, the earthquake may be triggered even if the ∆CFS is slightly greater than zero if the stresses before the mainshock are very close to Coulomb failure.…”

Effects of large historical earthquakes, viscous relaxation, and tectonic loading on the 2008 Wenchuan earthquake

“…Herein we refer to an earthquake fault as a zone with finite thickness [ Evans , 1990; Caine et al , 1996; Schulz and Evans , 2000; Li et al , 2002; Gudmundsson , 2004]. Thus in a mechanical model, the occurrence of an earthquake may be considered as material softening/weakening or damage in the fault zone, which may be simulated by reducing the shear modulus of the material in the fault zone [ Hu et al , 2009a, 2009b]. …”

“…To investigate the effects of large historical earthquakes, viscous relaxation, and tectonic loading on the Wenchuan earthquake, we used a procedure proposed by Hu et al [2009a, 2009b]: (1) Construct a geologic model with earthquake faults using the finite element method. (2) Obtain an initial stress field and calculate the initial earthquake triggering factor C before the first earthquake.…”

The effect of beach slope on the tsunami run-up induced by thrust fault earthquakes

“…V 1 represents the volume occupied by the fault zone with a width of 300m, a maximum depth of 7km and a dip angle of 10°. We assume that, before the earthquake, the fault zone has the same material properties as those of the solid seafloor; in the simulation, an earthquake a procedure used successively in Hu et al (2009) [10]. V 4 , a zone 10km wide on both the left and the right sides of the model and 5km thick at the bottom, is set up to absorb the reflected waves.…”

“…Second, the shear modulus in the fault zone V 1 is reduced to induce an earthquake. This procedure has been applied successfully by Hu et al (2009) [10] to study earthquake faulting and stress transfer in southern California. The amount of reduction in the shear modulus may be constrained by the observed shear displacement in the field.…”