Two thin middle-crust low-velocity zones imaged in the Chuan-Dian region of southeastern Tibetan Plateau and their tectonic implications  

作　　者：Long LI Xin WANG Guangbing HOU Yuan LING Yinshuang AI 

机构地区：[1]Key Laboratory of Earth and Planetary Physics,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China [2]College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China [3]Innovation Academy for Earth Science,Chinese Academy of Sciences,Beijing 100029,China

出　　处：《Science China Earth Sciences》2024年第5期1675-1686,共12页中国科学（地球科学英文版）

基　　金：supported by the National Key Research and Development Program of China(Grant No.2017YFC1500302);the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB18000000);the Young Elite Scientists Sponsorship Program by China Association for Science and Technology(Grant No.2020QNRC001)。

摘　　要：Intracrustal low-velocity zones(LVZs)indicate a mechanically weak crust and are widely observed in the southeast margin of the Tibetan Plateau.However,their spatial distributions and formation mechanisms remain controversial.To investigate their distribution and detailed morphology of the LVZs in the southeastern Tibetan Plateau,here we used teleseismic events and continuous waveform data recorded by 40 broadband seismic stations newly deployed in the Sichuan-Yunnan region from December 2018 to October 2020.A total of 12,924 high-quality P-wave receiver functions and 5–40 s fundamental Rayleigh surface wave phase velocity dispersion curves from ambient noise cross-correlation functions were obtained.The Swave velocity model at a depth interval of 0–100 km in the study area was inverted by using the trans-dimensional Markov chain Monte Carlo strategy to jointly invert the complementary data of the receiver function waveform and Rayleigh surface wave phase velocity dispersion.Our results show that there are two separate LVZs(~3.5 km/s)surrounding the rigid Daliangshan subblock at crustal depths of approximately 30–40 km,providing new constraints on the geometry of the LVZs in our study region.The two LVZs obtained in this study may represent the middle crustal flow channels,through which the material in the center of the Tibetan Plateau extrudes to its southeast margin.Blocked by the rigid Sichuan Basin and the spindle-like Daliangshan subblock,the material continues to flow southward through the mechanically weak middle crustal channels surrounding the Daliangshan subblock.In addition,the existence of thin LVZs in the middle crust plays an important role in understanding the decoupling between the upper and lower crust in the study area.It also provides new constraint on the complex tectonic deformation process of the southeastern margin of the Tibetan Plateau caused by the collision and compression of the Indian and the Eurasian plates.

关 键 词：Southeastern Tibetan Plateau Joint inversion Intracrustal low-velocity zone Mid-crustal channel flow 

分 类 号：P548[天文地球—构造地质学]