Tectonics of the eastern Asia and the western Pacific as seen by GPS observations

Abstract

Instantaneous tectonic motions in the eastern Asia and in the western Pacific have been measured by the Global Positioning Sustem. For this purpose, a continuous tracking network in the area named as the Western Pacific Integrated Network of GPS (WING) has been established. Obtained distribution of site velocities clearly suggests that oceanic plates such as Pacific and Philippine Sea plates are moving mostly as rigid, while the continental plate deforms considerably. Then, the Euler vector of the Philippine Sea plate was estimated using GPS velocities at Okino Torishima and other islands. In order to derive more detailed velocity field in east Asia, many of published velocity fields were combined so that they are consistent at the commonly occupied sites in the least squares sense. Results clearly show tectonic collision of Indian subcontinent toward Eurasia. Moreover, it is evident that the intruded lithosphere is extruding toward east showing acute bend of velocities in the north of Tibet. The effect of collision looks propagates towards far-east to Korea and Japan. Geographical Survey Institute of Japan recently established a nationwide dense GPS array consisting of about 1000 permanent sites. The velocity field obtained from this network clearly portrays effects of the surrounding plates.