Profiling of crustal deformation across the southwest Japan arc

日本西南弧的地壳变形剖面

基本信息

批准号：
14340133
负责人：
TABEI Takao
金额：
$ 7.36万
依托单位：
Kochi University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-14340133/
关键词：
GPS observation Philippine Sea plate Median Tectonic Line Crustal deformation Active fault Plate coupling

项目摘要

The main purpose of this study is to delineate detailed pattern of three-dimensional crustal deformation in the Nankai subduction zone, southwest Japan. Ongoing interseismic deformation in this region is a mixture of short-term crustal shortening in the direction of oblique convergence of the Philippine Sea plate and permanent lateral movement of the forearc block along the Median Tectonic Line(MTL). We constructed two dense Global Positioning System(GPS) networks in the eastern and western parts of Shikoku Island that extended from the Pacific coast to Chugoku district across the MTL. The networks have been configured so that both strain partitioning in the direction of plate convergence and slip distribution along the MTL can be detected. We determined crustal velocities at 36 sites together with those at the nationwide continuous GPS stations in the vicinity.In order to decompose the deformation field into short-term and permanent components, we explicitly model the plate subduction using multi-rectangular fault segments, newly determined plate convergence vector, and depth-dependent plate coupling estimated from thermal model. Residual velocity field after subtracting the crustal shortening caused by plate subduction shows a lateral movement of the forearc block at a rate of about 5mm/yr along the MTL. Closer inspection shows that fault plane of the MTL inclines northward and its upper part is strongly locked to the depth of 15km while stationary slip is occurring below 15km. Plate coupling at the Nankai Trough is estimated very strong in a shallower zone to the depth of 25km, gradually decreasing with depth, and almost disappears below 35km.We published papers in Earth, Planets and Spaces and made several presentations at the meetings of the Seismological Society of Japan, the Geodetic Society of Japan, the American Geophysical Union, and others.

这项研究的主要目的是描绘日本西南部南海俯冲带三维地壳变形的详细模式。该地区持续的震间变形是菲律宾海板块倾斜汇聚方向的短期地壳缩短和弧前块体沿中位构造线（MTL）的永久侧向运动的混合体。我们在四国岛的东部和西部建设了两个密集的全球定位系统（GPS）网络，从太平洋沿岸穿过MTL延伸到中国地区。网络的配置使得可以检测板块收敛方向上的应变分配和沿 MTL 的滑移分布。我们确定了 36 个地点以及附近全国连续 GPS 站的地壳速度。为了将变形场分解为短期和永久分量，我们使用新确定的多矩形断层段明确地模拟板块俯冲板收敛向量，以及根据热模型估计的与深度相关的板耦合。减去板块俯冲引起的地壳缩短后的剩余速度场显示，弧前块体沿 MTL 以约 5 毫米/年的速度进行侧向运动。仔细观察发现，MTL断层面向北倾斜，其上部在15km深度处被强烈锁定，而在15km以下则发生静止滑移。据估计，南海海槽的板块耦合在 25 公里以下的较浅区域非常强烈，随着深度的增加逐渐减弱，在 35 公里以下几乎消失。我们在 Earth、Planets 和 Spaces 上发表了论文，并在地震学会议上做了多次演讲日本学会、日本大地测量学会、美国地球物理学会等。