HR: 1340h
AN: T13E-1633    [Abstracts]
TI: A Reference Crustal and Plate-Boundary Velocity Model of Japan
AU: * Ishise, M
EM: ishise@eri.u-tokyo.ac.jp
AF: ERI, Univ. Tokyo, 1-1-1, Yayoi, Bunkyoku, 113-0032, Japan
AU: Koketsu, K
EM: koketsu@eri.u-tokyo.ac.jp
AF: ERI, Univ. Tokyo, 1-1-1, Yayoi, Bunkyoku, 113-0032, Japan
AU: Miyake, H
EM: hiroe@eri.u-tokyo.ac.jp
AF: ERI, Univ. Tokyo, 1-1-1, Yayoi, Bunkyoku, 113-0032, Japan
AB: The study of velocity structure using earthquake data has been remarkably progressed by development of seismic observation networks, improvement of the methodology, and increase in processing power. Recent studies on 3D velocity structures have produced tomographic images with resolution of a few kilometers (e.g., Matsubara et al., 2005; Nakamichi et al., 2007). In addition to these traveltime analyses, waveform studies such as receiver function analyses have been developed to image the configuration of continental Moho and oceanic plate boundaries (e.g., Yamauchi et al., 2003; Shiomi et al., 2004). Reflection and refraction surveys with controled sources have also been providing information on 2D and 3D velocity structures (e.g., Sato et al., 2005; Special Project for Earthquake Disaster Mitigation in Urban Areas). Thus, plenty of structural property models exist over the Japan islands, but the validity of an individual model is confined to its study area. Therefore, it is essential to build a reference crustal and plate-boundary velocity model for the whole Japan by combining them all together. If this sort of reference velocity model over the Japan islands is available under a unified criterion, it will be valuable for many fields of seismology and Earth sciences. We here construct a reference crustal and plate-boundary velocity model of Japan by integrating 2D models from seismic profiling and receiver functions, 3D models of seismic tomography, and other geophysical data such as gravity anomalies. The goal of this study is to construct a 3D laterally heterogeneous seismic velocity structure model, which clarifies the topography of the Conrad and Moho discontinuities and shapes of the oceanic plates, like the SCEC Unified Velocity Model (e.g., Magistrale et al., 1996). We first make a preliminary Japan model by compiling information on the topography of the Conrad and Moho discontinuities and subducting plates. To this end, we collect 2D seismic velocity models obtained by seismic profiling of reflection/refraction surveys and receiver function analyses, and then integrate them to a 3D velocity model, using complementary information on 3D structures, such as 3D boundary shapes obtained by travel time and gravity anomaly analyses. At this stage, maintaining local structural continuity is a key challenge in the process. We also have to clarify major tectonic features such as the Median Tectonic Line and the Itoigawa-Shizuoka Tectonic Line, and consider the continuity between land-based and offshore models. The integrated 3D reference model will improve the reliability of strong ground motion prediction. Improvements will be the most critical for large-scale ground motion simulations for plate-boundary earthquakes in the Nankai and Tokai regions, which can cause strong shaking in major metropolitan areas of Japan. So, this modeling should be one of the most essential parts of earthquake damage mitigation in Japan.
DE: 0905 Continental structures (8109, 8110)
DE: 1219 Gravity anomalies and Earth structure (0920, 7205, 7240)
DE: 7240 Subduction zones (1207, 1219, 1240)
DE: 7270 Tomography (6982, 8180)
DE: 7299 General or miscellaneous
SC: Tectonophysics [T]
MN: 2007 Fall Meeting