Tectonics of the Western Pacific Area using GPS

为了研究西太平洋地区的构造，建立了一个区域GPS连续跟踪网。在研究期间，建立了以下研究中心：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、俄罗斯的海参崴和巴布亚新几内亚的莫尔兹比港。连同在日本石垣岛和帕劳的科罗尔已建立的地点，我们现在有八个地点可用于上述研究目的。大多数场址布设的PC和MO系统积累了数据。从1995年7月起，我们利用这些资料，描绘了该地区的位移速度矢量。为此，除了上述站点外，我们还合并了IGS（国际地球动力学GPS服务）的其他站点，以获得更好的区域覆盖和致密化。分析中采用Bernese软件Ver4.0，结合IGS精密轨道，采用无基准策略得到的结果表明：1马尼拉站向西北方向移动，表明菲律宾海板块的汇聚作用; 2石垣站向南移动，表明活动弧后之一的冲绳海槽的张开; 3关岛的位移速率与预期的菲律宾海板块刚性运动相比太小，表明马里亚纳弧后张开的影响。4远东亚洲大陆的所有地点，如大田，上海等，表现为向东向北东方向位移，反映了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.