HR: 0800h
AN: S21B-0570    [Abstracts]
TI: Dynamic Source Modeling of the Miyagi-oki Earthquakes
AU: * Kimura, T
EM: tkimura@eri.u-tokyo.ac.jp
AF: ERI, Univ. Tokyo, 1-1-1, Yayoi, Bunkyo, Tokyo, 113-0032, Japan
AU: Koketsu, K
EM: koketsu@eri.u-tokyo.ac.jp
AF: ERI, Univ. Tokyo, 1-1-1, Yayoi, Bunkyo, Tokyo, 113-0032, Japan
AU: Miyake, H
EM: hiroe@eri.u-tokyo.ac.jp
AF: ERI, Univ. Tokyo, 1-1-1, Yayoi, Bunkyo, Tokyo, 113-0032, Japan
AU: Wu, C
EM: wu@bosai.go.jp
AF: NIED, 3-1, Tennodai, Tsukuba, 305-0006, Japan
AU: Miyatake, T
EM: miyatake@eri.u-tokyo.ac.jp
AF: ERI, Univ. Tokyo, 1-1-1, Yayoi, Bunkyo, Tokyo, 113-0032, Japan
AB: Historical and seismic records indicate that interplate earthquakes with magnitude of ~7.5 have occurred repeatedly in the Miyagi-oki region, northeastern Japan, with a recurrence interval of ~37 years. The 1978 Miyagi-oki earthquake occurred, with magnitude of 7.4, and 27 years later, the 2005 event occurred in this region with magnitude of 7.2. Wu et al. [submitted] estimated rupture processes of the two events using teleseismic and strong motion records. Both events ruptured from the same hypocenters. The 1978 event consists of southern two asperities near the hypocenter and northern large asperity, and the 2005 event repeatedly ruptured only the southern two asperities. Estimation of dynamic source parameters of the two events may offer a key to understanding of reccurrence and interaction between asperities of interplate earthquakes. In this study, we construct dynamic source models of the Miyagi-oki earthquakes and evaluate dynamic source parameters, especially fracture energy, G_C, which would be able to be evaluated stably. The dynamic source models are constructed based on kinematic source models. We simulate the spontaneous dynamic rupture on a fault embedded in an infinite homogeneous elastic medium by using the forth-order finite difference method with 3D staggered grid. The grid interval and time-step size are 0.2 km and 0.01 sec, respectively. We assume the slip-weakening model with D_C of 0.4 m as a constitutive law on the fault and modify distributions of static stress drop and strength excess by forward modeling. We could construct a dynamic source model of the 2005 event in which the rupture process agrees with kinematic source model in the first asperity, which is close to the rupture nucleation point. In this model, the value of G_C is about 3 MJ/m² in the first asperity. This value is comparable to those of large earthquakes estimated by previous studies [Beroza & Spudich, 1988; Ide, 2002]. However, significant rupture did not occur in the second asperity 40 km away from the rupture nucleation point in the down-dip direction, because the stress did not increase enough to exceed the assumed strength in the second asperity. We will consider conditions for rupture in the second asperity.
DE: 7209 Earthquake dynamics (1242)
SC: Seismology [S]
MN: 2007 Fall Meeting