著者

岡村 行信

出版者

石油技術協会

雑誌

石油技術協会誌 (ISSN:03709868)

巻号頁・発行日

vol.65, no.1, pp.40-47, 2000

被引用文献数

11

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The eastern margin of the Japan Sea has rifted in the early Miocene. Then it hascompressed during the late Pliocene through the Quaternary. This change of stress caused basininversion along the margin, but the inversion structures vary mainly due to difference of therifting structures. In this paper, three types of basin inversion were defined. Type A basininversion is characterized by simple inversion of half grabens. Miocene normal faults reactivatedas reverse faults and the whole grabens have been uplifted. Many basin inversions of this typehave been widely formed in the Sado Ridge and Mogami Trough in the southern part of theeastern margin of the Japan Sea, to the west of the Tohoku Arc. Type B basin inversion isdefined by anticlinoriums in the major rift basins along the coastal zone of the Tohoku arc. Therifts have been partly uplifted by reverse faults and asymmetric anticlines, suggesting that partsof the extensional faults in the rifts have reactivated. Type C basin inversion forms the OkushiriRidge which continues in the N-S direction along the eastern margin of the Japan Basin to thewest of Hokkaido. It is not clear that the ridge has overprinted on the preexisting extensionalfaults. Reverse faults in the three types of basin inversion are accompanied by asymmetricanticlines or anticlinoriums. The profiles of the anticlines suggest that hinges of the anticlineshave been fixed during the growth of the anticlines. These structure and growth pattern of theanticlines can be explained by listric reverse faults and detachments at 10-20km in depth. Thegeologic structure related with extensional tectonics are generally obscure due to the lack ofpre-rift sedimentary sequences and extensive activity of volcanism in the rifting stage.Consequentry, it is difficult to clarify the relationship of the major fault systems between theextensional and compressional stages.