The high topography of the Tibetan Plateau was generated by the Cenozoic India‐Eurasia collision. A high‐resolution shear wave velocity model can provide improved understanding of the Tibetan structure and crustal deformation with complicated tectonic evolution. Based on continuous seismic observations at approximately 400 stations, we collected over 10,000 Rayleigh wave phase velocity dispersion curves extracted from ambient noise cross‐correlation functions. A direct surface wave inversion method was applied to obtain an S wave velocity model of the Tibetan crust. A heterogeneous structure including several prominent low‐velocity zones (LVZs) and relatively narrow low‐velocity bands connecting the LVZs is revealed. Our model shows significant crustal low‐velocity structures with lateral variations along the Himalayan front. In the eastern segment of the Lhasa terrane, the LVZ is spatially correlated with Miocene porphyry Cu deposits, which are probably related to strong tearing of the Indian lithosphere, while preexisting weak zones contribute to the LVZs in the western segment. Meanwhile, the LVZ along the Bangong‐Nujiang suture could be considered as a channel for eastward extrusion of ductile material, that is, crustal flow on geological timescales. This “flow” in the middle‐lower crust probably contributed to the formation of the V‐shaped conjugate strike‐slip fault system in central Tibet. The development of conjugate strike‐slip faults, however, ceased near 90°E, since the eastward “flow” was blocked by an intracrustal high‐velocity block in Amdo. This preexisting rigid zone (containing the Amdo microcontinent) hence influences the pattern of material transport inside the Tibetan crust and the deformation of the plateau.

SUMMARY: Between 2008 and 2013, the Ms 8.0 Wenchuan earthquake and the Ms 7.0 Lushan earthquake occurred successively in the Longmenshan fault zone. Their aftershocks delineated a prominent seismic gap approximately 50 km long, hereafter referred to as the WLSG. The possibility of an event of Ms 7.0 or above occurring in the WLSG is a matter of great concern. In this study, we estimated the change of Coulomb failure stress (ΔCFS) along the WLSG caused by historical earthquakes in the last 300 yr. Our results revealed that 20 major earthquakes cast a stress shadow on the WLSG before 2008 (−148.7 to −7.0 kPa), hindering the rupture of the Wenchuan earthquake and the Lushan earthquake. The Wenchuan earthquake had an important influence on the stress redistribution of the WLSG, resulting in significant stress increase (14.7 to 337.5 kPa). As of 2018, although the negative ΔCFS caused by historical earthquakes (especially the Dayi earthquake) pushed the southern end of the WLSG away from failure, the positive peak ΔCFS of 323.0 kPa greatly encouraged the rupture of the northern WLSG. The small afterslip and weak microseismicity indicate that the WLSG is a stress barrier with high seismic potential, which can explain the mechanism of rupture termination of the Wenchuan earthquake and the Lushan earthquake.

The Fenhe‐Weihe Rift (FWR) system is one of the most active rift zones in east China, and plays an important role in the reactivation of the North China Craton. In this work, a high‐resolution 3‐D lithospheric S wave velocity model of the FWR is built by joint inversion of receiver functions and ambient noise. Strong correlation between topography and tectonic features is observed at shallow depths. At great depths, strong heterogeneities are observed along the FWR: (1) high‐velocity anomalies emerge beneath the Weihe and Taiyuan basins in the lower crust; (2) two high‐velocity anomalies are imaged in the uppermost mantle beneath the south to central FWR; and (3) two strong large‐scale, low‐velocity zones are observed beneath the north Trans‐North China Oregon: one is at ~60 km and the other one is much larger with a deeper source. Based on the petrologic properties, geochemical analyses, and seismic images obtained in this work, we propose that the rifting mechanisms between the south and north FWR are different. In the south, the rifting could be mainly caused by the passive effects from the uplift of the Tibetan Plateau, while in the north the rifting is due to the combined effects of the asthenosphere upwelling and the counterclockwise rotation of the Ordos block. The uppermost mantle high‐velocity anomalies underneath the south to central part of the FWR could be the remnants of strong ancient cratonic root, and act as mechanical barriers to block the rifting processes between the south and north FWR.