• 责任者：Wang Xiaolong (State Key Laboratory of Earthquake Dynamics ; Institute of Geology ; China Earthquake Administration ; Beijing 100029 ; China) ; Ma Shengli
• 刊名：Chinese Journal of Geophysics
• 出版年：2013
• 卷期：56(12)
• 关键词：地壳结构 ; crustal structure ; 速度结构 ; velocity structure ; 长江三峡 ; Yangtze Three Gorgees
• 页码：p.4113-4124
• 图表：7 illus., 38 refs.
• 分类号：0400
• issnNo：ISSN0001-5733
• isbnNo：CN11-2074/P

     We investigate the crustal velocity structure o{ the Sichuan basin based on ambientnoise tomography using continuous waveform data recorded by the Chongqing telemetry network and other permanent stations in the region from January to December of 2012. By extracting the dispersion information of Rayleigh waves from empirical Green functions （EGFs）, we invert the phase velocity of surface waves for periods from 5 s to 40 s and further estimate S-wave velocity in 3-dimensions. The results of phase velocity at periods of 5 s and 10 s indicate that the Sichuan basin is characterized by thick sedimentary layers, of which the thickness is relatively small in the central basin. The phase velocity at periods around 20 s mainly reflects the S-wave velocity structure in middle crust, which demonstrates increasing velocity with increasing depth. The phase velocity at the period about 35 s is totally high indicating that the Yangtze plate has a rigid lower crust in the region. Particularly, the distinct high velocity anomalies around the Wuling Mountains from Jishou to Changde are most likely related to the paleo-volcanic chain of Jiangnan paleo-continent activity which caused a large amount of basic and ultrabasic mantle material intruded into the crust. With greater mechanical strength, it plays a certain impediment to southward escaping of material on the west of the Wuling Mountains gradient zone of gravity anomalies （Yunnan-Guizhou Plateau and the mountainous topography of the west of Hubei and Hunan）, which is just located in the transition zone of the second step and the third step of China~s topography. The obtained 3-dimensions S-wave velocity model is corresponding to the main geological structures within and surrounding the Sichuan basin, and thus it is meaningful for further study on the cteep structure and seismicity in the region.