Distinct Orogenic Processes in the South‐ and North‐Central Tien Shan From Receiver Functions

The high relief in the Tien Shan mountains is the product of compressional tectonics due to transmitted stress from the India-Eurasia collision. However, it remains an enigma regarding the geodynamic processes at depth, which are responsible for this surface reconstruction.

In the study of Zhang et al. (2020), they take advantage of the receiver functions derived from an orogen‐perpendicular array of closely spaced seismograph stations and implement H-k-c and CCP techniques to investigate the crustal structure across the Central Tien Shan.

The results delineate detailed morphology of the Moho discontinuity there, which provides strong evidence for distinct orogenic processes on two sides of the mountains. In the North‐Central Tien Shan, the imaged Moho doublet suggests the underthrusting of the Kazakh Shield accommodating the convergence there. A southward‐dipping diffuse Moho is imaged in the South‐Central Tien Shan (SCTS), in contrast with the relatively flat and sharp Moho beneath the Tarim Basin. This feature along with the large Moho offset beneath the South‐Boundary Fault suggests that the shortening and thickening of the Tien Shan crust rather than the underthrusting of the Tarim Basin are responsible for the uplift of the SCTS.

Figure 1. Image showing the CCP results. Red and blue colors show positive and negative amplitudes, respectively. Moho depths obtained by H‐k‐c analysis are marked by yellow circles, consistent with the Moho conversions from CCP analysis. Black dashed lines denote the preferred Moho geometry, which show significant variations in different tectonic segments.

The first author of this study is Bingfeng Zhang, a Ph.D. student in the corresponding author’s (Prof. Xuewei Bao) group. Other author includes Prof. Yixian Xu at Zhejiang University. This research was supported by the Natural Science Foundation of China (41774045, 41830212).

For details: Zhang, B., Bao, X., & Xu, Y. (2020). Distinct orogenic processes in the south‐ and north‐central tien shan from receiver functions. Geophysical Research Letters, 47, e2019GL086941. https://doi.org/10.1029/2019GL086941