日本地球惑星科学連合2015年大会

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口頭発表

セッション記号 S (固体地球科学) » S-CG 固体地球科学複合領域・一般

[S-CG57] 変動帯の構造・進化とダイナミクス

2015年5月27日(水) 14:15 〜 16:00 A06 (アパホテル&リゾート 東京ベイ幕張)

コンビーナ:*竹下 徹(北海道大学大学院理学院自然史科学専攻)、佐藤 比呂志(東京大学地震研究所地震予知研究センター)、尾鼻 浩一郎(海洋研究開発機構 地震津波海域観測研究開発センター)、西村 卓也(京都大学防災研究所)、深畑 幸俊(京都大学防災研究所)、加藤 愛太郎(名古屋大学大学院環境学研究科)、武藤 潤(東北大学大学院理学研究科地学専攻)、佐藤 活志(京都大学大学院理学研究科地球惑星科学専攻)、小平 秀一(海洋研究開発機構 地球内部ダイナミクス領域)、鷺谷 威(名古屋大学減災連携研究センター)、石山 達也(東京大学地震研究所)、松原 誠(防災科学技術研究所)、池田 安隆(東京大学大学院理学系研究科地球惑星科学専攻)、座長:蔵下 英司(東京大学地震研究所)

15:54 〜 15:57

[SCG57-P14] 日本海東縁地域における地形発達から見積もられる活褶曲発達場の移動

ポスター講演3分口頭発表枠

*大坪 誠1宮川 歩夢1 (1.産総研)

キーワード:褶曲, 断層, 地形, 地震, 変形, 歪み集中帯

The Quaternary tectonics of the Japan arc is characterized by strongly crustal deformation, whose mode and rate are quite different from those of the preceding late Pliocene. The Tohoku district, on the eastern margin of the Japan Sea, lies within a strongly compressive area that has been experiencing large, contractional, crustal deformations, since the late Pliocene (Sato and Amano, 1991). Fold-and-thrust structures (Sato, 1989) and fold-topographic structures with distributed reverse faults (e.g., Okamura et al., 1995) have developed in response to this contractional deformation. Geodetic surveys in the Tohoku district have detected zones with a high rate of horizontal strain (Sagiya et al., 2000). When the contractional deformation continues to the present, the high strain rate zones at the geological and geodetic scales should be overlapped. However, the high horizontal strain-rates recognized at geological and geodetic time-scales are spatially heterogeneous. Rates are consistent in the Niigata region, in the southwestern part of the Tohoku district, but not in the Akita region in the northwestern part of the district. There is, therefore, a need to constrain the spatial differences in the horizontal strain-rate between the geological and geodetic time-scales, in order to understand regional tectonic differences across the district.
We focus here on the erosional and topographic evolution of fold structures developed since the late Pliocene in the Akita and Niigata regions. We measured the distance between the fold hinge lines and the mountain ridge lines. We targeted 44 folds that were activated since the late Pliocene, comprising 12 and 32 folds in the Akita and Niigata regions, respectively. Spatial variations in the normalized deviations are consistent with the systematic eastward migration of fold growth in the area. The topographic behavior indicates that the landward migrating of the fold growth is generally constant.

References: Ellis, M.A., Densmore, A.L., 2006. Geological Society of America Special Papers 398, 251-266; Lave, J., Avouac, J.-P., 2000. Journal of Geophysical Research: Solid Earth 105 (B3) 5735-5770; Merritts, D., Ellis, M., 1994. Journal of Geophysical Research: Solid Earth 99 (B6), 12135-12141; Okamura, Y., Watanabe, M., Morijiri, R., Satoh, M., 1995. Island Arc 4, 166-181; Sagiya, T., Miyazaki, S., Tada, T., 2000. Pure and Applied Geophysics 157, 2303-2322; Sato, H., 1989. Memoirs of the Geological Society of Japan 32, 257-268; Sato, H., 1994. Journal of Geophysical Research: Solid Earth 99 (B11), 22261-22274; Sato, H., Amano, K., 1991. Sedimentary Geology 74, 323-343; Sibson, R.H., 2009. Tectonophysics 473, 404-416.