第55回ジオダイナミクスセミナー
　　　Geodynamics　Seminar

要　旨
　In this work we have tried to adopt a new approach to detect and collect later phases associated with the Moho discontinuity and use them to study the lateral variations of the crustal thickness in southwest (SW) Japan. We first compute synthetic seismograms for local earthquakes taking into account the focal mechanism solutions estimated from first motion data. Then we compare the synthetics with the observed waveforms to detect the major later phases in seismograms of shallow crustal earthquakes in SW Japan. Taking advantage of the high-quality and great quantity of Hi-net waveform data now available, we have detected around 1700 Moho reflected phases (PmP and SmS) from shallow events in SW Japan. We estimated the crustal thickness in the study area using travel-time differences between these later phases and the first P and S arrivals. Our results show that the Moho is deeper in Chubu district and becomes shallower along the coast of the Japan Sea and the coast of the Pacific Ocean. Areas around Awaji Island and Osaka Bay show a thinner crust.


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