Research of tectonics in Asia and Pacific based on synthetic analysis of GPS data

该项目的目的是综合亚太地区已公布的GPS速度场来圈定该地区的详细构造速度场。为此，我们使用了七篇以上的文章在ITRF97参照系中以最小二乘意义拟合常占用IGS站点的速度。所得到的速度场参照稳定的欧亚大陆，得到了构造上易读的地图。由此得到的地图显示，亚洲大陆的广大地区主要受印度次大陆碰撞的影响。此外，在中国中部的鲜水河-小江断裂带周围发现了剧烈的顺时针旋转，将印度支那-中国半岛推向南方。我们用Hashimoto和Jackson(1993)提出的块体-断层模型来模拟形变场。结果清楚地显示了由于印度的碰撞，该地区的块状运动和中国大陆的扇形扩张。为了研究中国块体的急性旋转对印度支那-中国半岛的影响，我们在泰国进行了GPS运动观测。泰国的估计速度没有显示出半岛中部有任何明显的变形。然而，形变似乎分布在横跨沿越南、老挝和中国边境的西北偏南方向的红河断裂的大范围内。另一方面，在中国以北，阿穆尔板块被假设解释蒙古和俄罗斯的小东移，尽管显然需要更详细的调查。

The purpose of the project was to synthesize published GPS velocity field in Asia and Pacific to delineate obtain a detailed tectonic velocity field of the area. To this end, we used more than seven articles to fit the velocities at the commonly occupied IGS sites in a least-square sense in ITRF97 reference frame. The obtained velocity field was referenced to the stable Eurasia to get tectonically easy-to-read map. Thus obtained map shows that the wide area of Asian continent is mostly affected by the collision of Indian sub-continent. More over, an acute clockwise rotation is found around the Xianshuihe-Xiaojiang fault zone in the central China, which push the Indo-China peninsula to south. We modeled the deformation field by the block-fault model introduced by Hashimoto and Jackson (1993). The result clearly showed blockwise motion of the area together with fan-shape spreading of the China continent due to the collision of India.In order to investigate the effect of acute rotation of China block to Indo-China peninsula, we conducted GPS campaign observation in Thailand. The estimated velocities in Thailand did not show any significant deformation in the central part of the peninsula. However, the deformation seemed to distribute in the wide area crossing the Red River fault that runs NW-SE along the Vietnam, Laos and China border. In the north of China, on the other hand, Amurian plate was hypothesized to interpret small eastward displacement in Mongolia and Russia, though more detailed investigation is clearly needed.