Crustal flow pattern beneath the Tibetan Plateau constrained by regional Lg-wave Q tomography

Two crustal low-velocity channels beneath SE Tibet revealed by joint inversion of Rayleigh wave dispersion and receiver functions

“…The mechanically weak midlower crust has also been supported by several lines of evidence from geophysical observations, such as intra-crustal LVZs (Bao et al, 2013;Ceylan et al, 2012;Fu et al, 2010;Li et al, 2008;Xu et al, 2013a;Xu and Song, 2010;Yang et al, 2012;Yao et al, 2008), low electrical resistivity in the mid-lower crust (Bai et al, 2010;Unsworth et al, 2005;Wei et al, 2001), high V p /V s ratios (Sun et al, 2014;Xu et al, 2007), high heat flow (Hu et al, 2000), and strong attenuation (Bao et al, 2011a;Zhao et al, 2013), indicating the existence of partial melt and viscosity reduction in the mid-lower crust and thus the possibility of crustal flow. In addition, strong positive radial anisotropy with faster horizontally polarized shear wave further suggests sub-horizontal alignment of mica and/or amphiboles in the crust due to ductile flow beneath SE Tibet (Huang et al, 2010;Shapiro et al, 2004;Xie et al, 2013).…”

Complex seismic anisotropy beneath western Tibet and its geodynamic implications

“…The existence of such flow is a debated issue (e.g., Tapponnier et al, 2001;Royden et al, 2008;Zhao et al, 2013;Zhang et al, 2014). The NE-SW oriented crustal anisotropy revealed by both the Pms and XKS phases provides additional support for the existence of such a flow, which is considered as the main cause for the uplift and growth of the Tibetan Plateau (Royden et al, 2008).…”

“…In spite of numerous studies, the 3-D distribution of the subducted Indian mantle lithosphere and the mechanisms responsible for the uplifting of the Plateau remain enigmatic (Yin and Harrison, 2000;Klemperer, 2006). While some studies advocate thickening of both the crustal and mantle parts of the lithosphere (Flesch et al, 2005), some others hypothesize that the uplift is mostly the result of crustal thickening associated with lower (and/or middle) crustal flow (Zhao and Morgan, 1987;Nelson et al, 1996;Klemperer, 2006;Royden et al, 2008;Zhao et al, 2013;Liu et al, 2014). The second hypothesis implies that the Indian * Corresponding author.…”

Analytical and numerical simulations of uplift processes at the Tibet-Sichuan boundary

“…Tomography results also show low-velocity zones in the lower crust (Meissner and Mooney 1998;Galvé et al 2006;Wang et al 2007;Yao et al 2008;Yang et al 2012;Liu et al 2014). Furthermore, small elastic thickness and high Q value of Tibetan plateau both support a weak lower crust for the Tibetan plateau (Jordan and Watts 2005;Wang et al 2007;Bao et al 2011;Zhao et al 2013). Third, the lower crust of the plateau has strong seismic anisotropy, where the velocity of SH wave is much higher than SV wave (Shapiro et al 2004;Huang et al 2010;Yao et al 2010).…”

“…At the eastern margin of the plateau, the flow of materials breaks into two branches due to the obstruction of Sichuan basin: one toward Ordos basin and the other toward Indo-China block with a clockwise rotation Zhao et al 2013). The elevation gradient varies significantly at the east boundary of Tibetan plateau.…”