第123回ジオダイナミクスセミナー
　　　Geodynamics　Seminar

　"Imaging the velocity structure and the lateral heterogeneity
　　 in Japan by waveform modelling and seismic tomography"
　　　　　　　　　
　　　講師：Mohamed F. Abdelwahed（愛媛大学博士３年）"

　　　　　　　　　　　　 　　　　　 　　　　　
　　　　　主催　：　愛媛大学地球深部ダイナミクス研究センター
　　　　　日時　：　２００５年３月２５日（金）17：00〜
　　　　　場所　：　愛媛大学理学部講義棟　２０１教室

要　旨
　The crustal structure beneath Japan is investigated through waveform modeling and seismic tomography studies. In southwestern Japan, the generalized ray theory (Helmberger, 1974, 1983) is used to optimize 1-D velocity models for twenty-nine individual paths. High-quality seismograms recorded by the Hi-net seismic network are used. Synthetic tests are conducted to study the effects of the different model parameters. The resulted synthetics match the observed seismograms well. Considerable variations of the Conrad and Moho depths are found in the study area. In Central Japan, seismic tomography (Zhao, 1992) is used to image the P-wave, S-wave and Poisson ratio perturbations using 42790 P and 46093 S-wave high-quality arrival times from 5107 events. Checkerboard resolution tests conducted in this study indicate that the spatial resolution is 10-15 km in the horizontal direction and 4-6 km in the vertical direction. The relationship between seismic tomography and the major tectonic features is investigated. Low-Vs and high-Poisson's ratio anomalies are visible beneath most of the active volcanoes up to 15 km depth. The majority of the earthquakes are associated with either the low-velocity patterns or at the transition between the high and low velocity patterns. Significant correlation between velocity perturbation patterns at shallow depths and fault distributions are found





　　　　　　　　問い合わせ先：山崎　大輔 　TEL　　　（089）927-8408
　　　 　　　　　　　　　　　　　　　　E-mail　　yamazaki@sci.ehime-u.ac.jp