Pn anisotropic tomography under the entire Tienshan orogenic belt

Lithospheric structure of the Tien Shan region constrained by joint inversion of receiver function and Rayleigh wave dispersion

“…Moreover, at the depths above ~40 km, the velocity contours from east to west show clear change when crossing the TFF, while at the depths from ~40 km to Moho, the velocity contours become uniform. The velocity contrast across the TFF may suggest the presence of a tectonic boundary between the western and central Tien Shan beneath the fault, which is generally consistent with previous studies (Li & Chen, ; Lei, ; Roecker et al., ; Zhou & Lei, ). However, the estimated depth extent of the fault in our study is ~40 km and is inconsistent with previous body‐wave tomographic studies (Lei, ; Roecker et al., ; Zhou & Lei, ).…”

“…GPS measurements in the Tien Shan and surrounding regions reveal that the Tien Shan is undergoing a significant north–south crustal shortening (Abdrakhmatov et al., ), which implies that the stress induced by the Indo–Asian collision (e.g., Deng et al., ) is transferred to the Tien Shan orogenic belt through the rigid Tarim Basin. In addition, the crustal movements from GPS observations are generally consistent with the directions of the regional maximum compressional stress, suggesting that the subduction of the Tarim Basin and Kazakh Shield could be one of the most important geodynamic sources in the mountain building beneath the Tien Shan (e.g., Lei & Zhao, ; Li et al., ; Roecker et al., ; Zhou & Lei, ). The far‐field effect of the transferring stress from the India–Asia collision and underthrusting of the Tarim and Kazakh lithosphere are consistent.…”

“…Moreover, the topography of the Moho interface above the low‐velocity anomaly shows clear uplift, possibly suggesting the intrusion of hot materials into the crust. We infer that the upwelling of the hot and wet material from the mantle may indeed play an important role in mountain building beneath the central Tien Shan (e.g., Lei, ; Roecker et al., ; Zhou & Lei, ).…”

“…The TFF, a prominent right‐lateral strike‐slip fault with a slip rate of 8–16 mm/a (Burtman, Skobelev, & Molnar, ), extends from the Tarim basin in the south to the Kazakh shield in the north (Figure ). Previous studies based on different geophysical techniques have demonstrated that the TFF is an important boundary between the central and western Tien Shan (e.g., Li & Chen, ; Lei & Zhao, ; Omuralieva, Nakajima, & Hasegawa, ; Roecker et al., ; Zhou & Lei, ). However, the vertical extent of the fault is still under dispute.…”

“…Several previous studies (e.g., Lei, ; Roecker et al., ; Zabelina et al., ) showed low‐velocity anomalies in the lower crust and uppermost mantle beneath the central Tien Shan, which have been attributed to the upwelling of hot mantle material induced by lithospheric delamination. The previous results argued that the upwelling of mantle material may have played an important role in mountain building (Lei, ; Roecker et al., ; Zhou & Lei, ), though the mechanism of mountain building in the Tien Shan is still controversial. GPS measurements in the Tien Shan and surrounding regions reveal that the Tien Shan is undergoing a significant north–south crustal shortening (Abdrakhmatov et al., ), which implies that the stress induced by the Indo–Asian collision (e.g., Deng et al., ) is transferred to the Tien Shan orogenic belt through the rigid Tarim Basin.…”