Intersected Structure and Superpose Tectonics between the Eastern Margin of Japan Sea and the Toyama Trough, central Japan

本研究利用多波束测深和侧扫声纳及海底剖面仪对日本海域进行了地貌调查，结果表明：(1)上新世及其后的褶皱和相关破裂作用发育了甲烷水合物的表层，浅至海底露出的最上层，供潜水器观测。可以肯定的是，在甲烷沿背斜轴线迁移和上涌的构造高地上，已经形成了类似于盐丘的水合物穹顶。在陆地上，我们继续进行GPS大地测量，以监测目前正在进行的地壳变形。研究结果证实了活动断裂在陆上和海上的分布，以及它们之间的交叉关系。我们对日本最活跃的断裂之一阿多舒川断裂系统的地震地质调查表明，在1858年的最近一次地震中，发震断裂的东半部也被激活，西段也被激活，这表明N-S方向的基底结构与NE-西南向的薄弱带新泻-神户构造带存在深部交汇。为了解决交汇动力学问题，我们将推动地球物理、大地测量学、地质学和其他物质科学对构造现象与孕震带下地壳构造现象的力学关系的综合综合研究。2008年及以后，我们参加了日本海东部边缘构造应变集中带五年研究和监测计划。

This study had conducted geomorphologic survey utilizing multi-narrow beam swath bathymetry and acoustic imaging by side scan sonar and sub-bottom profiler in the Japan sea-area, As the results the following were elucidated (1) The Pliocene and later folding and related fracturing had developed surfacial layers of methane hydrate as shallow as the uppermost layer is outcropped on the sea bottom to be observed by the submersible vehicle. It was assured that hydrate domes similar to salt domes have been formed on structural highs where migration and upwelling of methane are localized along the anticline axes.On land, we have continued our GPS geodetic monitoring of the present-day ongoing crustal deformation. The results confirmed the distribution of active faults across both regions in land and sea, and also intersecting relationships among them. Our seismo-geological surveys on the Atotsugawa fault system, one of the most active faults in Japan, made clear that the eastern-half segment of seismogenic faults had also been activated at the latest event in 1858 as well as the western, suggesting the deep intersection of basement structure in a N-S trend and NE-SW trending weak zone called the Niigata-Kobe tectonic belt.In order to resolve the dynamics of intersection, we will promote an integrated comprehensive study among geophysics, geodesy, geology and other material sciences on the mechanical relationship between tectonic phenomena and those in the lower crust beneath seismogenic zone. In 2008 and after, we join the five-year research and monitoring program for the zone of tectonic strain concentration along the eastern margin of Japan Sea.