Tectonics of the Western Pacific Area using GPS

为研究西太平洋地区的大地构造，建立了区域GPS连续跟踪网。在研究期间，建立了以下站点：日本的马库斯、密克罗尼西亚的特鲁克、菲律宾的马尼拉、韩国的大田、俄罗斯的符拉迪沃斯托克和巴布亚新几内亚的莫尔兹比港。连同在日本石垣和帕劳的科罗尔建立的其他地点，我们现在有八个地点可用于上述研究目的。数据积累在部署在大多数站点的PC和MO系统中。它们每隔两到三个月定期邮寄给东京大学地震研究所。我们自1995年7月以来一直使用这样的数据来圈定该地区的位移速度矢量。为此，除了上述地点外，我们还纳入了IGS(国际地球动力学全球定位系统服务)的其他地点，以提高地区覆盖率和密度。在分析中，我们使用了Bernese软件Ver4.0和IGS精密轨道。1马尼拉台址向西北方向移动，提示菲律宾海板块汇聚的影响；2石垣台址近南移，暗示冲绳海槽的开放，这是一个活跃的后弧区；3关岛的位移速率与菲律宾海板块预期的刚性运动相比太小，表明马里亚纳岛弧后开放的影响；4远东亚洲大陆的所有场址，如大田、上海等，都表现出东向至东北向的位移，表明印度大陆向欧亚大陆碰撞的影响。

In order to investigate tectonics in the western Pacific area, a regional GPS continuous tracking network has been constructed. During the research period, following sites were established ; Marcus in Japan, Truk in Micronesia, Manila in Philippine, Taejeon in Korea, Vladivostok in Russia and Port Moresby in Papua New Guinea. Together with otherwise established sites in Ishigaki in Japan and Koror in Palau, we now have eight sites to be used for the above research purpose. Data are accumulated in the PC and MO system emplaced at most of sites. They are sent by regular mail basis for each two to three months to the Earthquake Research Institute, University of Tokyo.We have used thus obtained data since July 1995, to delineate displacement velocity vectors in the region. For this purpose, adding to above sites, we incorporated other sites of IGS (International GPS Service for Geodynamics) for better regional coverage and densification. At the analysis we used Bernese software Ver4.0 together with IGS precise orbits.Results obtained by the fiducial free strategy indicates the followings ;1 Manila site is moving toward northwest suggesting effects of the convergence of the Philippine Sea plate,2 Ishigaki site is moving nearly south suggesting the opening of the Okinawa trough, which is one of active back-arcs,3 Displacement rate of Guam is too small comparing with expected rigid motion of the Philippine Sea plate, suggesting the effects of Mariana backarc opening,4 All sites in the far eastern Asian continent, such as Taejeon, Shanghai etc., shows eastward to north-eastward displacement, suggesting effects of the collision of Indian continent toward the Eurasian continent.