GeoFEM Kinematic Earthquake Cycle Simulation in Southwest Japan

Abstract

We construct a viscoelastic FEM model with 3-D configuration of the subducting Philippine Sea plate in Southwest Japan to simulate recent 300-year kinematic earthquake cycles along the Nankai-Suruga-Sagami trough, based on the kinematic earthquake cycle model. This 300-year simulation contains a series of three great interplate earthquakes. The inclusion of viscoelasticity produces characteristic velocity field during earthquake cycles regardless of the assumed constant plate coupling throughout the interseismic period. Just after the occurrence of interplate earthquakes, the viscoelastic relaxation creates the seaward motion in the inland region. In the middle period, the seaward motion gradually decreases, and the resultant velocity field is similar to the elastic one. Later, just before the next interplate earthquake, displacements due to the interplate coupling in the viscoelastic material are distributed more broadly in the forearc region than in the purely elastic one, since the viscoelastic relaxation due to the previous earthquake mostly disappears. The effects of such interplate earthquake cycles on five major inland faults in southwest Japan, where large intraplate earthquakes occurred during this period, are quantitatively evaluated using the Coulomb failure function (CFF). The calculated change in CFF successfully predicts the occurrence of the 1995 Kobe earthquake (M$7). The occurrence of other inland earthquakes, however, cannot be explained by the calculated changes in CFF, and especially the 1891 Nobi earthquake (M$8), the largest inland earthquake in Japan, which occurred at the time close to the local minimum of CFF. This implies that further improvements are necessary for our FEM modeling, such as the modeling of steady east-west compressive force and stress interactions between the inland faults.

Effect of elastic inhomogeneity on the surface displacements in the northeastern Japan: Based on three-dimensional numerical modeling

“…The finite element method is a very powerful tool for calculation of deformation and/or stresses in heterogeneous materials, and has been successfully applied in various fields of science. The method has also been frequently used in the solid earth science, for example, to calculate the stresses and/or deformation in plate-subduction and/or plate-collision zones (e.g., Sato et al, 1981Sato et al, , 1996Sato, 1988Sato, , 1989Hashimoto, 1984Hashimoto, , 1985Hashimoto, 1989a, 1989b Miyashita, 1997; Suito and Hirahara, 1999;Hyodo and Hirahara, 2004). In this study, we have used a parallelized finite element code GeoFEM developed at the Research Organization for Information Science and Technology (RIST) (e.g., Iizuka et al, 2002).…”

Deformation of Mild Steel Plate with Linear Cracks due to Horizontal Compression

“…The second type is the plate model which has downward tension on Plate 1 (UMB -X2; UMB-X5; UMB-X8; UMB-PB-X; UMB-PB-X2). The plate models of the second type are mostly composed of material of the crust of the Philippine Sea plate [4,5], in which a transition zone UMB (Upper Mantle Boundary) is placed between Plate 1 and LMS. The material of rubber-like-elasticity [6] is assumed for PB and UMB.…”

Afterslip distribution following the 2003 Tokachioki earthquake: An estimation based on the Green’s functions for an inhomogeneous elastic space with subsurface structure

“…Hence, in order to incorporate the inhomogeneity due to such complication of subsurface structure, we adopt a 3D finite element technique in the calculation of GFs. For the calculation, we use the GeoFEM, a parallelized finite element code, developed at the Research Organization for Information Science and Technology (RIST) (e.g., Iizuka et al, 2002;Hyodo and Hirahara, 2004 …”