The hypothesis proposed by Nakamura (1983) that the North-Eastern Japan is a part of the North-American Plate has been re-examined from geological and geomorphological veiw points. One of the difficulties is that active faults are not found along the entire length of the Itoigawa-Shizuoka Tectonic Line which is considered as the boundary between rigid plates. The beginning of the convergence at the Itoigawa-ShizuokaTectonic Line is much older than the age speculated by SENO (1987) . An alternative hypothesis that the Itoigawa-Shizuoka Tectonic Line is a moribund plate boundary is proposed.
Tokihiko, MATSUDA2) and Yoshihiro KINUGASA3)The Quaternary age of the Japanese islands is characterized by renewed, intense crustal deformation, whose mode and rate are quite different from those of the preceding late Tertiary. In view of these characteristics, the Quaternary period of the Japanese islands can be labelled as follows: a) an age of increasing topographic relief, b) an age of land emergence, c) an age of block faulting, d) an age of mm/year tectonics, e) an age of compression tectonics, and f) age of plate collision.The crustal movements contain a) intermittent fault movement due to brittle fracture of the crust, and b) elastic and c) non-elastic secular deformations.An archipelago-wide regional emergence in the Quaternary is recognized, which is probably due to regional non-elastic deformation.in mode and rate of deformatiom in the middle of the Quaternary, which may be partly explained by collisions of the Izu block with Honshu and of northeast Japan with southwest Japan since the middle Quaternary.
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