中国科学院地质与地球物理研究所艾印双团队，报道了青藏高原东南部川-滇地区两个薄中地壳低速带成像及其构造意义。2024年3月25日出版的《中国科学：地球科学》杂志发表了这项成果。

壳内低速带(LVZs)以地壳力学性质较弱为特征，广泛分布于青藏高原东南边缘地区。然而，它们的空间分布和形成机制仍存在争议。

为了探究青藏高原东南部LVZs的分布和详细形态，研究人员使用了2018年12月至2020年10月川滇地区新部署的，40个宽带地震台站记录的远震事件和连续波形数据。从环境噪声相互关系函数中获得了总共12,924个高质量的P波接收器函数，和5-40s基本瑞利面波相速度频散曲线。研究采用跨维马尔科夫链蒙特卡罗策略，联合反演接收函数波形与瑞利面波相速度频散的互补数据，反演0-100km深度区间的横波速度模型。

结果表明，在岩体深度约为30-40km的刚性大凉山子地块周围存在两个独立的LVZs(约3.5km/s)，为研究区域LVZs的几何形状提供了新的限制条件。本研究获得的两个LVZs可能代表了青藏高原中部物质向东南边缘挤压的中地壳流动通道。受刚性四川盆地和纺锤状的大凉山子地块的阻挡，物质通过大凉山子地块周围机械薄弱的中部地壳通道继续向南流动。此外，中地壳薄层LVZs的存在对研究区上、下地壳的解耦具有重要意义，这也为青藏高原东南缘以印度板块和欧亚板块碰撞挤压为主导的，复杂构造变形过程提供了新的约束。

附：英文原文

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

Author: Long LI, Xin WANG, Guangbing HOU, Yuan LING, Yinshuang AI

Issue&Volume: 2024/03/25

Abstract: 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 5–40s fundamental Rayleigh surface wave phase velocity dispersion curves from ambient noise cross-correlation functions were obtained. The S-wave velocity model at a depth interval of 0–100km 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 (~3.5km/s) surrounding the rigid Daliangshan subblock at crustal depths of approximately 30–40km, 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.

DOI: 10.1007/s11430-023-1256-0

Source: https://www.sciengine.com/10.1007/s11430-023-1256-0