Surface Wave Tomography In China And Adjacent Areas

This paper deals with the high resolution surface wave tomography in China and adjacent areas. 1000 events (7.0≥M≥5.0) recorded at 78 digital seismic stations form network in Asia, Europe and west Pacific regions are used in this paper. 10,000 accurate Rayleigh surface and 3,280 Love surface dispersion curves are selected and employed for inversion. The high resolution 3-D shear wave velocity images in this area are constructed by inversion dispersion and show a notable lateral variation in the crust and upper mantle.In this process, the author has worked out automatic drawing picture and reading dispersion data program and then used it to deal with 30,000 seismic records.The images of S wave velocity indicate that the evolution and geodynamic process is so different between the eastern part and western part of the East Asia and West Pacific marginal seas by the boundary of longitude 110°E. The western part is the thickening convergent lithosphere caused by Indian subcontinent collision with the Eurasian continent, and the eastern part is disassembly caused by the lithosphere thinning and extension arising from intrusion of asthenospheric material.There exists a giant low velocity belt in the upper mantle with length of about 8,000 km, width of about 2,500-4,000 km from sea of Okhotsk, Kuril basin, Sea of Japan, North China and South China, South China Sea to Philippine Sea.From the images of Love wave, we can know that there are differences of velocity among the major tectonic units in this area. China land is divided into East belt and West belt, North blocks and South blocks. Some blocks are more obvious as India plate, Tarim basin east Europe block, Siberian plate, North-China block, Yangtze, etc. Landscape orientation asymmetry is clear in active tectonic units.