地震学报（英文版）2002，Vol.15Issue(1)：1-17,17.
A study on 3-D velocity structure of crust and upper mantle in Sichuan-Yunnan region, China*
A study on 3-D velocity structure of crust and upper mantle in Sichuan-Yunnan region, China*
摘要
Abstract
Based on the first arrival P and S data of 4 625 regional earthquakes recorded at 174 stations dispersed in the Yunnan and Sichuan Provinces, the 3-D velocity structure of crust and upper mantle in the region is determined, incorporating with previous deep geophysical data. In the upper crust, a positive anomaly velocity zone exists in the Sichuan basin, whereas a negative anomaly velocity zone exists in the western Sichuan plateau. The boundary between the positive and negative anomaly zones is the Longmenshan fault zone. The images of lower crust and upper mantle in the Longmenshan fault, Xianshuihe fault, Honghe fault and others show the characteristic of tectonic boundary, indicating that the faults likely penetrate the Moho discontinuity. The negative velocity anomalies at the depth of 50 km in the Tengchong volcanic area and the Panxi tectonic zone appear to be associated with the temperature and composition variations in the upper mantle. The overall features of the crustal and the upper mantle structures in the Sichuan-Yunnan region are the lower average velocity in both crust and uppermost mantle, the large crustal thickness variations, and the existence of high conductivity layer in the crust or/and upper mantle, and higher geothermal value. All these features are closely related to the collision between the India and the Asia plates. The crustal velocity in the Sichuan-Yunnan rhombic block generally shows normal value or positive anomaly, while the negative anomaly exists in the area along the large strike-slip faults as the block boundary. It is conducive to the crustal block side-pressing out along the faults. In the major seismic zones, the seismicity is relative to the negative anomaly velocity. Most strong earthquakes occurred in the upper-mid crust with positive anomaly or normal velocity, where the negative anomaly zone generally exists below.关键词
regional earthquake/Moho discontinuity/3-D velocity structure/network method/plate collision/seismicityKey words
regional earthquake/Moho discontinuity/3-D velocity structure/network method/plate collision/seismicity分类
天文与地球科学引用本文复制引用
..A study on 3-D velocity structure of crust and upper mantle in Sichuan-Yunnan region, China*[J].地震学报（英文版）,2002,15(1):1-17,17.基金项目
National Scientific and Technological Development Program (95-973-02-02), the Climb Program (95-S-05-01) of National Scientific and Technological Ministry of China, and the State Natural Sciences Foundation of China (49874021). （95-973-02-02）
