| In this paper the author studies the theory and method of refraction tomography at uppermost mantle. The images of P- and S-wave velocity lateral variation are rebuilded at uppermost mantle beneath China continent, and anisotropy of P-wave velocities are obtained on the basis of Pn and Sn travel time data in China and adjacent area by tomography technique.1 , Travel times of 91138 Pn arrivals recorded from China and adjacent regional earthquakes are inverted in a tomographic study to map the lateral variations and anisotropy of Pn velocity of the uppermost mantle. Average P-wave velocity 8.05km/s is got and velocities vary from -0.29km/s(3.6%) to +0.31km/s(3.9%). On the whole, the velocities are different in eastern and western China. In the west, high velocities are predominant. (1) Abnormal high velocities mainly exist around Qingzang plateau, especially in Junggar, Tarim, Qaidam and Sichuan basin, velocities there are higher than 8.2 km/s. (2) Low velocities only exist in the middle of Qingzang plateau and western part of Sichuan and Yunnan region.In eastern China, low velocities are predominant. (1) The whole North-China and most northeastern China have low velocities, especially in North-China basin, Bohai bay and Shanxi rift valley, the velocities are abnormally low. The lowest velocity reaches 7.8km/s. (2) In southern China, the velocities are near average value. A little low velocities exist in the regions such as Zhujiangkou, middle of Guangxi, Lushan and so on. A little high velocities exist in the middle region lied to the south of Yangzi river and to the north of Zhujiang river. When the anisotropy is not taken into account, the obtained image almost has the same variation pattern with that when anisotropy is considered. But Pn velocities are not well consistent with geology for the former than the later.Pn anisotropy is less remarkable in eastern China than western China. In general, there are three large regions, where anisotropy is significant. In these region rays are dense, so anisotropy are credible. (1) In Tarim basin, the direction of faster velocity is oriented NW-SE. (2) In the east of Qingzang plateau and west of Sichuan basin, the direction of faster velocity is oriented NWW-SEE, (3) In erdos terra, the direction of faster velocity is oriented E-W.The resolution of Pn image eastmated by use of Checkerboard method indicates: velocity resolution reaches 3O X 3O, anisotropy resolution reaches 4O X 4O in most regions, the resolution is low in marginal region.2, The image of Sn-wave velocity lateral variation is reconstructed in Chinacontinent by tomography method using 43646 Sn rays. The average Sn velocity is 4.55km/s. the velocity perturbations vary from -0.14 km/s (-3.1%) to +0.15 km/s (3.3%). In gerneral, Sn velocities are higher in western China than in eastern China. In the west, there are some obvious high velocity regions, such as tectonically stabe Tarim, Junggar, Turpan, Hami basin and east of Qaidam basin, Sichuan basin and to its south, Taiwan Strait and so on. High velocities also exist in Erdos. In eastern China, low velocities exist in northern Shanxi, North-China basin, to the east of Bohai Bay, northern Tan-Lu fault, Taiwan and its east. In addition, the low velocities lie in western part of Sichuan and Yunnan, Lushan and northern Qingzang Plateau. The resolution of Sn velocity by Checkerboard test is 4O X 4O in most regions,and 3O X 3O in dense ray regions, such as Xinjiang and Sichuan basin. The velocity ratio or Poisson ratio variaton can be obtained by comparing Pn and Sn velocities.3 , In comparing Pn and Sn velocity variation with geology, we will find that high velocity regions always exist in old stable basin and terra, but low velocity regions lie in active extensional basin, volcano area and magmatic rock regions. Velocity variation is positively correlated with crust thickness and negatively correlated with Earth's heatflow. The linear regression equation of velocity, crust thichness and heatflow is obtained. The regression coefficient dV/...
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