Subsurface structure and faulting of the Median Tectonic Line, southwest Japan

日本西南部中部构造线的地下结构和断层活动

• 批准号: 10440129
• 负责人: TABEI Takao
• 金额: $ 6.02万
• 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: 1998
• 资助国家: 日本
• 起止时间: 1998 至 2000
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-10440129/
• 关键词: Median Tectonic Line; GPS measurement; Crustal deformation; Fault lock and slip; Fault deep structure; 固着・すべり分布; 地殻変動モデリング

Main purpose of this study is to clarify deep structure and slip distribution of the Median Tectonic Line (MTL) in southwest Japan from dense GPS traverse measurements at the surface. We constructed 22 stations along a 220km-long line and conducted three campaign measurements in 1998-2000. We determined horizontal crustal velocities at 64 sites in total including adjacent continuous stations of the nationwide network. Campaign velocities obtained are so accurate as to show very good accordance to the velocities from continuous measurements.We quantitatively discriminated deformation field into two categories : elastic deformation caused by the subduction of the Philippine Sea plate and block-like movements across the MTL.We made both forward and inversion modelings. In the former we extracted block motion across the MTL, fault locking in the uppermost part and steady slip at depth by calculating elastic deformation from a plate subduction model and subtracting it from the observed velocity field In the latter we simultaneously estimated plate subduction, block motion across the MTL and slip deficit in the uppermost part of MTL.Two modelings gave the nearly same results :1. Southern block of the MTL moves westward at a rate of about 5mm/yr relative to the northern one, consistent to the geological right-lateral slip rate of 5-10mm/yr.2. The block boundary does not agree with the stuface trace of the MTL, clearly displaced 20-30km to the north.3. The above results are interpreted that the fault plane of MTL dips into the north at an angle of 30-40 degrees, and the uppermost part of MTL is locked to the depth of 15-20km and steady right-lateral slip occurs below. These results have been presented at several meetings in Japan and USA.The manuscript for the publication in the international journal is being prepared.

这项研究的主要目的是阐明日本西南部构造线（MTL）的深层结构和滑移分布，从表面的密集的GPS遍历测量值。我们沿着220公里长的线建造了22个站，并在1998 - 2000年进行了三项竞选测量。我们确定了总共64个地点的水平地壳速度，包括全国性网络的相邻连续站。获得的运动速度是如此准确，以至于表现出很好的规定，从连续测量的速度显示出非常好的速度。我们定量区分了变形场分为两类：弹性变形，由菲律宾海板的俯冲以及MTL跨MTL的like板状运动引起。在前者中，我们通过计算板缩减模型中的弹性变形，并从后者中观察到的速度场中减去弹性变形，从而在最上部提取了块运动，并在深度下稳定滑移，我们同时估计了板套的俯冲，跨MTL运动跨MTL和滑移的障碍。 MTL的南部块以大约5mm/年的速度向西移动，相对于北部的速度约为5mm/年，与5-10mm/yr.2的地质右边滑动速率一致。块边界与MTL的Stuface轨迹一致，显然是向北20-30公里。3。上述结果被解释为MTL的断层平面以30-40度的角度向北浸入北部，而MTL的最高部分锁定到15-20km的深度，而稳定的右侧滑动发生在下方。这些结果已在日本和美国的几次会议上提出。