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| | Abstract | | Special session:A retrospective review was conducted of subsurface investigations in major sedimentary basins. As part of grant business in Japan, Tokyo metropolitan government, Chiba prefecture, etc. have conducted seismic reflection and refraction surveys in Kanto plains in 1998-2004. Aichi prefecture and Mie prefecture have also conducted seismic surveys in Noubi plains in 1998-2004. Those results are announced by Headquarters for Earthquake Research Promotion in Japan. We have discussed a difficulty of the field data acquisition over densely populated area and explained how we have overcome the difficulty for the deep seismic profiling there in the previous presentation. By delineating the sedimentary-basin structure up to a depth of 4,000m in metropolitan areas, these projects have contributed to provide the fundamental database for promoting earthquake disaster prevention countermeasures, as well as changing citizen's consciousness for disaster prevention. The data has been rapidly accumulated during the last two decades. There are still remaining areas where seismic survey has not yet conducted or where the subsurface image is too fragmentary to evaluate concealed active faults. To reveal a whole structure of the basin to predict strong ground motions for scenario earthquakes, successive projects are expected in future. |
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