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《Computerized Tomography Theory and Applications》 2008-02
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Tomographic Imaging of P and S Wave Velocity Structures Beneath North China and its Vicinity

WANG Zhi-shuo~(1,2) WANG Chun-yong~1 ZENG Rong-sheng~1 WANG Xi-li~1 1.Institute of Geophysics,China Earthquake Adiministration,Beijing 100081,China 2.Earthquake Administration of Henan Province,Zhengzhou 450016,China  
The regional travel-time data from 475 seismic stations in the North China and its vicinity were used to inverse the P and S velocity structures of the crust and uppermost mantle.The pseudobending ray tracing algorithm was used to calculate the travel times.The large and sparse system of observation equations is solved by using the LSQR algorithm.According to the checker-board tests,reliable inversion results were obtained for a parameterized model with grid size of 0.5°by 0.5°in the horizontal directions and 5 nodes of 1,10,25,42 and 60 km in depth.The Yangtze Block and the Sino-Korean Block are located in two sides of the Qinling-Dabie orogenic belt.The differences of velocity structure between two Blocks are that lower velocity anomaly exists in most part of the Sino-Korean Block,while velocity distribution is normal in the Yangtze Block.This indicates that the Yangtze Block is relative stable,and the Sino-Korean Block is still active,where strong earthquakes have frequently occurred.Main features of the'velocity structure in the Sino-Korean Block are that major tectonic belts (such as Yanshan uplift,Taihangshan piedmont fault belt,Tanlu fault belt,and Qinling-Dabie orogenic belt)are located in the low velocity areas or the transition zone from low velocity area to high velocity area in the crust and upper mantle.In the Tangshan earthquake area,low velocity anomaly commonly exists at the depth of 25 km,42 km and 60 km,which may imply that the hot material in upper mantle upweUs,and then stops to the lower part of upper crust.
【Fund】: 科技部科技基础性资助项目(华北精细结构探测);; 中国地震局重点项目(中国大陆数字壳幔结构);; 国家自然科学基金(40334041,90814001)
【CateGory Index】: P315.2
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