HR: 16:45h
AN: S14C-04    [Abstracts]
TI: Source Modeling of Subduction-Zone Earthquakes and Long-Period Ground Motion Validation in the Tokyo Metropolitan Area
AU: * Miyake, H
EM: hiroe@eri.u-tokyo.ac.jp
AF: Earthquake Research Institute, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113- 0032, Japan
AU: Koketsu, K
EM: koketsu@eri.u-tokyo.ac.jp
AF: Earthquake Research Institute, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113- 0032, Japan
AU: Furumura, T
EM: furumura@eri.u-tokyo.ac.jp
AF: Earthquake Research Institute, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113- 0032, Japan
AB: The national seismic hazard map of Japan indicates 30 year probability in the Tokyo metropolitan area controlled by megathrust earthquakes along the Philippine sea plate. Four major subduction-zone earthquakes are Kanto (Mw 7.9), northern Tokyo-bay (Mw 7.0 or greater), Tokai (Mw 8.0), and Tonankai (Mw 8.2) earthquakes. We have experienced the 1923 Kanto and 1944 Tonakai earthquakes, however the rest of two are hypothetical earthquakes. Source modeling and realistic ground-motion prediction for the earthquakes are quite important for disaster mitigation and hazard assessment in the Tokyo metropolitan area. We have carried out ground motion validation for the Kanto earthquake [Miyake et al., 2005] using physics-based source model along the new geometry of the plate, and 3D velocity model based on geophysical surveys. We here present ground motion validation for the Tokai and Tonankai earthquakes under the framework of the Special Project for Earthquake Disaster Mitigation in Urban Areas (2002-2006) and the Special Project for Earthquake Disaster Mitigation in Metropolitan Tokyo ‚`rea (2007-2011). The source process of the 1944 Tonankai earthquake was inferred from strong-motion and teleseismic data by Ichinose et al. [2003] and Yamanaka [2004]. For the hypothetical Tokai earthquake, Matsumura [2002] proposed locked zones figured out from seismicity which could be candidates for future asperities. Using the locations of the asperities, we constructed a characterized source model consisting of asperities and background area. The size and slip of the asperities are constrained by the source scaling of asperities for subduction-zone earthquakes, where the scaling is based on the compilation of past slip inversion results. The stress drop was adjusted so that asperities for long-period ground motions behave as strong motion generation areas for short- period ground motions. We adopted the 3D velocity model beneath the Tokyo metropolitan area constructed by integrating refraction, reflection, borehole, microtremor, and gravity data as well as ground motion spectra [e.g., Tanaka et al., 2005]. This model is upgraded with the velocity models of plate and crustal structures as well as subsurface-shallow structure. Ground motion validation for the Tokai and Tonankai earthquakes are performed. Long-period components are simulated by the FDM, and short-period ones by the stochastic Green's function method with the site amplification factors. Broadband ground motion time histories are reproduced by the hybrid method with the matching period of 3 s. We confirmed the distribution of simulated long-period ground motions are well reflected to the basement depth of the velocity structure, and oceanic structure with the sedimentary wedge which contributes to further propagation of the long-period ground motions. Even the seismic intensity is limited to 4 or 5- in the JMA scale, long-period ground motions are significantly developed in the Kanto basin. This indicates significant impact of long-period ground motion from the future subduction-zone earthquakes against the Tokyo metropolitan area.
UR: http://www.eri.u-tokyo.ac.jp/hiroe/
DE: 7212 Earthquake ground motions and engineering seismology
DE: 7215 Earthquake source observations (1240)
DE: 7240 Subduction zones (1207, 1219, 1240)
SC: Seismology [S]
MN: 2007 Fall Meeting