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Study on the Extension Tectonics of Northeast Honshu Arc Just Before 15 Ma.

本州岛东北弧15 Ma之前的伸展构造研究。

基本信息

批准号：
01540622
负责人：
OTSUKI Kenshiro
金额：
$ 0.51万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1989
资助国家：
日本
起止时间：
1989 至 1990
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-01540622/
关键词：
Japan Sea opening half-grabens asymmetry of half-grabens strain gradient laws of convergence rate of plates Philippine Sea Plate 前期中新世日本海の拡大ハ-フグラ-ベンの幅温度勾配粗粒堆積物

项目摘要

1) Half-grabens were active in Northeast Japan in the period from 23 Ma to 14 Ma. They trend NNW to NNE, and have a width of about 10 km. The grabens were filled by thick and coarse clastic sediments.2) Newly investigated grabens in the Oguni area Yamagata Prefecture and the Ani area of Akita Prefecture have nearly same characteristics as others in Northeast Japan.3) The analysis of the metalliferous veins suggests that one of the middle to Late Miocene Principal stress trendeds ENE-WSW and was weakly compressional and another was NNW-SSE in trend and tensional. This stress field suggests that not only Southwest Japan but also Northeast Japan were suffered by the subduction of the Philippine Sea Plate.4) The early Miocene half-grabens in Northeast Japan are west side down in the Pacific side and east side down in Japan Sea side. Our new sand box experiments testified that the normal faults with fault plane dipping toward the high strain region are selectively grown, and that the degree of the asymmetry depends positively on the magnitude of the strain gradient. These results suggest that there was a zone of maximum tensional strain along the Ou backbone region during the early Miocene.5) The laws of convergence rate of plates (Otsuki, 1989) and the Paleomagnetic data from the Philippine Sea Plate suggest that not only Southwest Japan but also Northeast Japan suffered the subduction of the Philippine Sea Plate, and that the development of the early Miocene half-grabens and the Japan Sea opening were due to the slow northward motion of the Philippine Sea Plate during the period from ca. 24 Ma to ca. 12 Ma.

1）23Ma至14Ma期间，日本东北部半地堑活动。其走向为 NNW 至 NNE，宽度约 10 公里。 2) 新调查的山形县小国地区和秋田县阿仁地区的地堑特征与日本东北地区其他地堑基本相同。 3) 含金属矿脉分析表明, 中新世中晚期主应力一为ENE-WSW, 弱挤压, 另一为NNW-SSE 紧张的。这个应力场表明，不仅日本西南部，而且日本东北部都受到菲律宾海板块俯冲的影响。4）日本东北部早中新世半地堑在太平洋一侧西侧向下，在日本海一侧东侧向下。我们的新砂箱实验证明，断层面向高应变区域倾斜的正断层是选择性生长的，并且不对称程度正取决于应变梯度的大小。这些结果表明，早中新世沿瓯骨干区域存在一个最大拉应变带。 5）板块收敛速度规律（Otsuki，1989）和菲律宾海板块的古地磁数据表明，不仅日本西南部，而且日本东北部都遭受了菲律宾海板块的俯冲，早中新世半地堑的发育和日本海的张开是由于菲律宾海板块的俯冲缓慢造成的。菲律宾海板块在大约从 1997 年开始向北移动24 Ma 至约。 12马。