活断層研究
Online ISSN : 2186-5337
Print ISSN : 0918-1024
ISSN-L : 0918-1024
論説
活断層の変位速度からみた日本弧のプレート配置
-特にアムールプレート南東縁に関して-
小松原 琢
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ジャーナル フリー

2015 年 2015 巻 43 号 p. 17-34

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抄録

The Japan arc system is one of the typical island arc systems in the globe. The framework of plate tectonics, however, is still disputable. The author tries to elucidate the tectonic framework of this island arc system from the view point of slip rate and evolution history of active faults.

In past few decades, we have accumulated knowledge on the active tectonics. Especially slip rate and deformation mode of active faults during the late Quaternary have been revealed by intensive works. The author integrates the mean slip rate and strain rate distribution and evolution history of active structures in the Japan arc system. The results show the followings.

1) Horizontal shortening rate around central Hokkaido is much lesser than around the Fossa Magna region.

2) Major horizontal strain occurs along the Japan Sea coastal area of the Northeastern Honshu, in the inner zone from the mid Honshu to the Kinki district (Niigata-Kobe Tectonic Zone) and along the Median Tectonic Line in the Shikoku Island.

3) The east-west shortening rate of the Niigata-Kobe Tectonic Zone is 5〜15mm/yr, and it is comparable to the dextral slip rate of the Median Tectonic Line in the Shikoku Island and convergence rate of the Amur Plate and Okhotsk (Northeastern Japan) Plate.

4) The extension and deepening of the Bikal rift zone which locates northwestern margin of the Amur Plate has occurred since the late Pleistocene, and it accelerated since the late Early Pleistocene. This development history is concurrent with the east-west shortening along the Niigata-Kobe Tectonic Zone and along the Median Tectonic Line.

5) Above mentioned facts indicate that the eastern margin of the Japan Sea area and the Niigata-Kobe Tectonic Zone is a broad plate boundary between the Amur Plate and the Northeast Japan and Southwest Japan Plates, has 200km-width, and is made up by numerous discontinuous active faults and tectonic basins. The southeastern boundary of Amur Plate would continue from the Median Tectonic Line in the Shikoku Island to the East China Sea via the mid-Kyushu Island. But its location in the Kyushu Island and East China Sea is still unidentified.

6) The subsidence dominant, reverse fault-related basins occur along the Japan Sea Coast in the northeastern Honshu Island and along the Niigata-Kobe Tectonic Zone. But the length of each basin and fault is less than 100 km. These phenomena are thought to be characters accompanied with incipient arc-arc collision.

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© 2015 日本活断層学会・活断層研究会
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