オホーツクプレート運動の地球物理学的検証とそのテクトニクスの研究

为了弄清鄂霍次克板块的运动，1996年至1998年在堪察加、萨哈林和哈巴罗夫斯克部署了一个新的全球定位系统网络。该网络由12个站点组成，这些站点在每个点都尽可能地连续运行。通过对截至1998年底的观测资料的分析，明确了鄂霍次克板块的存在。此外，该项目还定量地确定了鄂霍次克板块附近的阿穆尔板块及其速度矢量的存在。得到了库页岛南部的速度矢量，这里表明鄂霍次克和阿木努尔板块的碰撞边界位于库页岛南部和北海道北部的内陆，而不是以前假设的位于日本海东部边缘的区域。测得的碰撞速率约为2 cm/年，是以前估计的两倍。在1995年北库页岛地震的震源区，自1996年以来每年夏季都进行时态地震观测。发现了断裂面上b值分布的特征，并用应力场强度的差异对其进行了解释。在库页岛南部地震带，南北走向明显。这可能是鄂霍次克和阿穆尔板块之间的分界线。Kmachatka的GPS网络于1996年和1997年部署，将提供详细的时间和空间数据，以确定鄂霍次克板块的运动。

To clarify the movement of Okhotsk Plate a new GPS network have been deployed in Kamchatka, Sakhalin and Khabarovsk from 1996 to 1998. The network consists of 12 stations that have been operating continuously at each point as possible. Existence of Okhotsk Plate is clearly concluded by analyzing the data obtained till the end of 1998. Furthermore existence of Amur Plate and its velocity vector which has been assumed nearby Okhotsk Plate by several authors based on geological and seismological data are also quantitatively determined by this project. Velocity vector of south Sakhalin obtained, here shows that the collision boundary between Okhotsk and Amnur Plates is located on inland of southern Sakhalin and northern Hokkaido instead of the former assumed zone located at the eastern margin of Japan Sea. The collision rate determined is about 2 cm/y that is two times greater than the former estimations.In the sourece region of the 1995 North Sakhalin Earthquake temporal seismic observations were carried out every summer since 1996. The characteristic property of b-value distribution on the fault plane was found and interpreted by the differences of strength of the stress field. In the South Sakhalin seismic belt trending North-South is clearely exposed. This may be the boundary between Okhotsk and Amur plates. GPS network in Kmachatka was deployed in 1996 and 1997 and will provide eough data in time and space for detail analysis to define the movement of Okhotsk plate.