| 講演要旨(和文) | | 特別セッション：地震災害に対する防災・減災のためには，活断層や活構造を含む深部地下構造形態の把握，断層の活動性評価，および，地下物性の詳細把握が重要である．また，地震工学的な観点から，地震基盤を含めた深部地盤までのP波，S波速度構造を知ることが，長大構造物等の耐震安全性を考える上では不可欠である．このため，地下構造調査における物理探査の役割は重要であり，特に，反射法および屈折法地震探査は，地下構造の地震動特性を把握したり，堆積層に埋没した活断層を抽出したりすることができるため，地震国である日本社会に大きく貢献している．本稿では，地震防災を目的として実施された地下構造調査について，関東平野や濃尾平野における調査事例を取り上げ，課題点や今後の方向性を議論する．特に，反射法および屈折法の有効性について，三次元地下構造モデルの作成や地震動の地域特性に関する議論を絡めながらレビューする． |
|
|
| | 講演要旨(英文) | | 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. |
|
|
|
| |
|