权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Study on Geoelectric-Geomagnetic and Thermal Structure of the Ryukyu Arc and East China Sea Region

琉球弧及东海地区地电地磁及热结构研究

基本信息

批准号：
02402013
负责人：
ISEZAKI N.
金额：
$ 20.29万
依托单位：
Faculty of Science, Chiba University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (A)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1991
项目状态：
已结题

项目摘要

1. Between 10Ma and 4Ma, the south Ryukyu Island Arc rotated about 19' clockwisely. If at this moment the Okinawa Trough was opened, the opening mode could not be "sea floor spreading". but like "continental rifting", because there is no observed magnetic anomaly lineation in the Okinawa Trough. The central part of Ryukyu Arc is thought not to rotate but to move without rotation, however, we could not get any paleomagnetic conclusion for the northern part of Ryukyu Arc.2. The other evidence for the "not seafloor spreading" mode is the result of of ocean bottom seismometer and air-gun research, that is, the seismological structure of the earth' crust in the south Okinawa Trough is not the oceanic type but the continental.3. Before 2Ma, the direction of the regional stress in the Ryukyu Arc changed from east-west to north-south. This change must correspond to the change of movement of the Philippine Sea Plate subducting beneath the Ryukyu Arc.4. The existence (size and potision) of the high electrical conductive layer or block beneath the Okinawa Trough will be soon made clear from the ocean bottom electric and magnetic research, which has been suggested from the study of mineralogical dehydration process occurring under the back arc associated with plate subduction.5. lnferring from the magnetic anomaly, seismic data, radiometric age and heat flow, the presently tectonically active region is the Yaeyama Graben where continental rifting has been occurring since 2Ma.

1. 10 ~ 4 Ma，南琉球岛弧顺时针旋转约19'。如果此时冲绳海槽被打开，其打开方式不可能是“海底扩张”。但由于在冲绳海槽没有观测到磁异常线理，因此类似于“大陆裂谷作用”。琉球弧的中部被认为是不旋转的，而是不旋转地运动，而琉球弧的北方部分则没有得到任何古地磁学结论.“非海底扩张”模式的另一个证据是海底地震仪和气枪研究的结果，即冲绳海槽南部地壳的地震学结构不是海洋型的，而是大陆型的. 2 Ma以前，琉球岛弧区域应力方向由东西向变为南北向。这一变化必然与菲律宾海板块俯冲到琉球弧下的运动变化相对应。通过对板块俯冲弧后矿物脱水过程的研究，提出了冲绳海槽底高导电层或块体的存在（大小和位置），并通过海底电、磁的研究，将很快得到明确.根据磁异常、地震资料、放射性年龄和大地热流等资料推断，现今构造活动区为八重山地堑，该地堑在2 Ma以来发生了大陆裂谷作用。