| 講演要旨(和文) | | 重力トモグラフィの手法を用いて和歌山県西部地域の重力異常から3次元密度構造を推定し,それとバックグラウンドの地震活動の関係を調べた.重磁力トモグラフィは,最適化アルゴリズムにシミュレーテッド・アニーリングを採用し,感度制御型平滑化拘束,アンサンブル解析,マルチモデル・アンサンブル解析,地質学的・地球物理学的事前情報のモデリングの補助アルゴリズムを導入し,解の非一意性・不安定性を大幅に低減させている.対象地域の密度構造と地震活動には,以下のような特徴的な関係が認められた.(1)浅部構造は東西走向,深部構造は北東-南西走向が卓越する,(2)地震活動のほとんどは,限られた密度領域(2.62-2.68g/cm3)で起きている.(3)Anticline構造に伴う震源クラスター (龍門岳東麓)はこの密度領域を越えてより深部まで達している. |
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| | 講演要旨(英文) | | Three-dimensional density structure at the western district of Wakayama Prefecture was determined using 3D gravimetric tomography technique, and the relation between this density structure and background seismic activity was studied. In gravimetic tomography, simulated annealing was applied as a optimization argorithm, and several supplementary argorithms were introduced in order to reduce the problems arising from nonuniqueness and instability of the solution, such as smoothness constraints with sensitivity control, ensemble analysis, and modeling of geologic and geophysical a priori information. This study revealed the close and characteristic relations between density structure and background seismic acitivity as follows. 1. The east-west trend is dominant in the shallow structure, while the northeast-southwest trend is dominant in the deep structure. 2. Most hypocenters are distributed within the limited zone with the particular density of 2.62-2.68g/cm3. 3. Seismicity extends to the greater depth at the axis of the anticline near the Ryoumon-Dake. |
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