地殻構造単位について : 東北日本近海の地殻変動
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概要
- 論文の詳細を見る
Thick sedimentary layers of Neogene age are distributed in the continental slope off the Pacific side of the Tohoku arc. Structural trends of the layers are almost parallel to the coastal line or to the axis of the Japan trench. One structural unit has a limited distribution of approximately 100 km long in N-S direction. The several structural blocks distinguished in the district (Fig. 1) show good concordance to the block structure deduced from the after-shock regions. Structural units at the shelf area are detected from the crustal movement at the shelf edge which is impressed at the base of the wave-cut terrace during the latest Pleistocene glaciation. Almost the same crustal unit is detected at the Japan sea side of the Tohoku arc. Tensional force may be predominant under the trench area, as is suggested by the antithetic faults at the sea-ward side trench slope and benches or narrow depressions caused by normal step faults at the land-ward side trench slope, nevertheless there are a few possibilities for the origin of the benches at the land-ward side trench slope. Overthrusting at the seismic plain which is suggested by the forcal mechanism solution of the Tokachi-oki earthquake in 1968 and by other data in the Aleutian and Chilean arc may be predominant under the continental slope. It may become gradually steeper to the sea bottom from the seismic plain. Therefore, crustal units may have oblique boundaries declined toward land at the outer Tohoku arc. Suzuki expressed the probability of crustal boundaries perpendicular in the inner Tohoku arc. This may suggest a possibility of difference in the stress condition between outer and inner Tohoku arc.
- 日本地質学会の論文
- 1974-07-31