HR: 0800h
AN: NG21C-0711    [Abstracts]
TI: Seismicity patterns and phase transitions in the two-dimensional spring-block model of earthquakes
AU: * Hasumi, T
EM: t-hasumi.1981@toki.waseda.jp
AF: Department of Applied Physics, Advanced School of Science and Engineering, Waseda University, 3-4-1, Okubo, Shinjyuku-ku, Tokyo, 169-8555, Japan
AU: Aizawa, Y
EM: aizawa@waseda.jp
AF: Department of Applied Physics, Advanced School of Science and Engineering, Waseda University, 3-4-1, Okubo, Shinjyuku-ku, Tokyo, 169-8555, Japan
AB: Earthquakes occur as a result of a fracture process and a frictional slip of a fault, and are categorized into nonlinear complex phenomena in a non-equilibrium open system. However, details of its physical mechanism remain open. On the contrary, many statistical properties of earthquakes have been known as empirical laws, for example, magnitude-frequency distribution called the Gutenberg-Richter (GR) law and the law of temporal decay of aftershocks (the Omori law). Furthermore, the spatio-temporal interval statistics have been studied recently. \par In the 1980s, Bak et al. proposed and emphasized the concept of self-organized criticality (SOC) in earthquake phenomena. Since then, many earthquake models based on the SOC have been proposed. The spring-block model proposed by Burridge and Knopoff is one of the useful model to discuss statistical properties of earthquakes. This model is modified to explain other statistical properties. \par In this presentation, we analyze statistical properties of earthquakes produced by the two-dimensional (2-D) spring-block model involving stick-slip behavior. The magnitude-frequency distribution, the inter-occurrence time statistics, and the hypocenter interval statistics are focused on. Comparing our results with seismicity in nature, we optimize the model parameters. We can show that the 2-D spring-block model can reproduce seismicity in nature in a restricted parameter regime. Additionally, the critical state of the system is presumed from the statistical properties of earthquakes. Then we construct phase diagrams to estimate a transition point. In the optimal case, the model exhibits the critical state. Therefore it is concluded that our results support the hypothesis that fault systems are in the state of self-organized criticality.
DE: 3270 Time series analysis (1872, 4277, 4475)
DE: 4430 Complex systems
DE: 4465 Phase transitions
DE: 4475 Scaling: spatial and temporal (1872, 3270, 4277)
DE: 4480 Self-organized criticality
SC: Nonlinear Geophysics [NG]
MN: 2007 Fall Meeting