Abstract
A new 3D velocity model of the crust and upper mantle in the southeastern (SE) margin of the Tibetan plateau was obtained by joint inversion of body- and surface-wave data. For the body-wave data, we used 7190 events recorded by 102 stations in the SE margin of the Tibetan plateau. The surface-wave data consist of Rayleigh wave phase velocity dispersion curves obtained from ambient noise cross-correlation analysis recorded by a dense array in the SE margin of the Tibetan plateau. The joint inversion clearly improves the vS model because it is constrained by both data types. The results show that at around 10 km depth there are two low-velocity anomalies embedded within three high-velocity bodies along the Longmenshan fault system. These high-velocity bodies correspond well with the Precambrian massifs, and the two located to the northeast of 2013 MS 7.0 Lushan earthquake are associated with high fault slip areas during the 2008 Wenchuan earthquake. The aftershock gap between 2013 Lushan earthquake and 2008 Wenchuan earthquake is associated with low-velocity anomalies, which also acts as a barrier zone for ruptures of two earthquakes. Generally large earthquakes (M ≥ 5) in the region occurring from 2008 to 2015 are located around the high-velocity zones, indicating that they may act as asperities for these large earthquakes. Joint inversion results also clearly show that there exist low-velocity or weak zones in the mid-lower crust, which are not evenly distributed beneath the SE margin of Tibetan plateau.
Highlights
The uplift and expansion of the Tibetan plateau (TP) are the result of the Indian-Eurasian collision since *50 million years ago (e.g., Yin and Harrison 2000; Royden et al 1997, 2008)
Two models have been proposed to explain how the LMS is formed: (1) crustal shortening and thickening model, in which extrusion along the lateral strike-slip faults caused by the subduction of Asian lithospheric mantle results in crustal shortening and uplift of the LMS (Tapponnier et al 2001); (2) crustal channel flow model, in which eastward ductile mid-crustal flow is obstructed by the rigid Sichuan basin (Royden et al 1997)
The horizontal slices of the vP and vS models inverted from body-wave data only, as well as the vS model jointly inverted by body- and surface-wave data at 5, 10, 17.5, 25 and 45 km depth are shown in Fig. 9, respectively
Summary
The uplift and expansion of the Tibetan plateau (TP) are the result of the Indian-Eurasian collision since *50 million years ago (e.g., Yin and Harrison 2000; Royden et al 1997, 2008). The eastern margin lacks large-scale young crustal shortening structures (Shen et al 2005). Two models have been proposed to explain how the LMS is formed: (1) crustal shortening and thickening model, in which extrusion along the lateral strike-slip faults caused by the subduction of Asian lithospheric mantle results in crustal shortening and uplift of the LMS (Tapponnier et al 2001); (2) crustal channel flow model, in which eastward ductile mid-crustal flow is obstructed by the rigid Sichuan basin (Royden et al 1997). An important difference between these two models is whether crust and mantle of the eastern plateau are decoupled. The highresolution velocity models from tomography can provide more constraints on these different models
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
