HR: 0830h
AN: NG41C-0077    [PDF]
TI: 3D Simulation of the Entire Process of Earthquake Generation at Subduction-Zone Plate Boundaries
AU: * Matsu'ura, M
EM: matsuura@eps.s.u-tokyo.ac.jp
AF: Department of Earth and Planetary Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033 Japan
AU: Hashimoto, C
EM: hashi@jamstec.go.jp
AF: Institute of Frontier Research for Earth Evolution, JAMSTEC, Kanazawa-ku, Yokohama, 236-0001 Japan
AU: Fukuyama, E
EM: fuku@bosai.go.jp
AF: National Research Institute for Earth and Disaster Prevention, Tennodai, Tsukuba, 237-0061 Japan
AB: In general, the entire process of earthquake generation consists of tectonic loading due to relative plate motion, quasi-static rupture nucleation, dynamic rupture propagation and stop, and restoration of fault strength. This process can be completely described by a coupled nonlinear system, which consists of an elastic/viscoelastic slip-response function that relates fault slip to shear stress change and a fault constitutive law that prescribes change in shear strength with fault slip and contact time. The shear stress and the shear strength are related with each other through boundary conditions on the fault. The driving force of this system is observed relative plate motion. The system to describe the earthquake generation cycle is conceptually quite simple. The complexity in practical modelling mainly comes from complexity in structure of the real earth. As a product of Crustal Activity Modelling Program (CAMP), which is one of the three main programs composing the Solid Earth Simulator project (1998-2003) promoted by MEXT, we have completed a physics-based predictive simulation model for the entire process of earthquake generation cycles in and around Japan, where the four plates of Pacific, North American, Philippine Sea and Eurasian are interacting with each other in a very complicated way. The total simulation system consists of a crust-mantle structure model, a tectonic loading model and a dynamic rupture model. First, we constructed a realistic 3D standard model of plate interfaces in and around Japan by applying an inversion technique to ISC hypocenter distribution data, and computed viscoelastic slip-response functions for this structure model. Second, we introduced the slip- and time-dependent fault constitutive law with an inherent strength-restoration mechanism as a basic equation governing the entire process of earthquake generation. Third, combining all these elements, we developed a simulation model for quasi-static stress accumulation due to relative plate motion. Fourth, we also developed a simulation model for dynamic rupture propagation on a 3D curved fault surface by applying BIEM. Finally, we connected the quasi-static stress accumulation model and the dynamic rupture propagation model through a simulation platform on the Earth Simulator, which is a high performance, massively parallel-processing computer system with 10 TB memories and 40 TFLOPS peak speed. Outputs of this simulation system are crustal deformation, internal stress changes and seismic wave radiation associated with seismic and/or aseismic slip at the plate interfaces. From comparison of these simulation outputs and observed data, we can extract useful information to estimate the past slip history and the present stress state at the plate interfaces by using an inversion technique. Given the past slip history and the present stress state, we can predict the next step fault slip and stress changes through computer simulation. In this presentation, as a demonstration, we show the result of 3D simulation of the entire process of earthquake generation cycle at the Tokachi-oki seismogenic region in northeast Japan.
DE: 3210 Modeling
DE: 3220 Nonlinear dynamics
DE: 7209 Earthquake dynamics and mechanics
DE: 7260 Theory and modeling
DE: 8123 Dynamics, seismotectonics
SC: Nonlinear Geophysics [NG]
MN: 2003 Fall Meeting