Crustal and Upper Mantle Velocity Structure of SE Tibet From Joint Inversion of Rayleigh Wave Phase Velocity and Teleseismic Body Wave Data

Abstract

The Tibetan Plateau is the world's largest and highest plateau resulting from the collision between the Indian and Eurasian plates that was initiated ∼50 Ma ago (Molnar & Tapponnier, 1975;Rowley, 1996). The intensive collision, subduction and related deep dynamic processes create significant crustal shortening and uplifting of the Plateau, accompanied with eastward extrusion of plateau materials (Harrison et al., 1992;Yin & Harrison, 2000). Due to the strong blockage of the rigid Yangtze Craton (YC) in the east, southeastern Tibet (SET) serves as one of the most important channels for the escape of plateau materials (Cook & Royden, 2008). All these tectonic

Crustal Structure and Anisotropy Measured by CHINArray and Implications for Complicated Deformation Mechanisms Beneath the Eastern Tibetan Margin

“…As river incision data supported the lower crust flow model for the crustal uplift in this area (Clark et al., 2005), many magnetotelluric and seismic investigations have been conducted to image the lower crustal flow. While magnetotelluric images suggested that high electrical conductivity structures in the lower crust are localized in two continuous channels that run roughly from north to south (Bai et al., 2010), seismic images, on the other hand, showed two distinct LVZs beneath the SYRB and the SCB (e.g., Bao et al., 2015; M. Chen et al., 2014; Y. Liu et al., 2023; Shen et al., 2016; Y. Yang et al., 2020; X. Yang et al., 2023; Zhang et al., 2020). The two LVZs seem to be separated by the inner zone of the ELIP and will be referred to as eLVZ and wLVZ, respectively (Figure 7b).…”

“…Therefore, the observed crustal anisotropy also disfavors the presence of an organized lower crust flow in the eLVZ area. In fact, all the most recent tomographic studies (e.g., Y. Yang et al., 2020; X. Yang et al., 2023; Zhang et al., 2020) showed that the eLVZ is disconnected from the wLVZ, suggesting that it has a different origin from the wLVZ, such as mantle upwelling (Z. Huang et al., 2015) or crustal thickening and partial melting in the mid‐lower crust (Zhang et al., 2020).…”

“…In fact, all the most recent tomographic studies (e.g., Y. Yang et al, 2020;X. Yang et al, 2023;Zhang et al, 2020) showed that the eLVZ is disconnected from the wLVZ, suggesting that it has a different origin from the wLVZ, such as mantle upwelling (Z.…”

“…Due to the low station density in the area as well as the limited ability of traveltime tomography in imaging low‐velocity structures, the lateral resolution of early traveltime tomography is relatively low. Recent deployment of the CHINArray and incorporation of ambient noise data, together with the improvement in seismic tomography have led to high resolution images of the crust beneath the eastern margin (e.g., Bao et al., 2015; Y. Liu et al., 2023; Shen et al., 2016; Y. Yang et al., 2020; X. Yang et al., 2023; Zhang et al., 2020). All the tomographic models showed a large scale low‐velocity anomaly beneath the SGB, which extends southward to the northern part of the SYRB.…”

“…Recent deployment of the CHINArray and incorporation of ambient noise data, together with the improvement in seismic tomography have led to high resolution images of the crust beneath the eastern margin (e.g., Bao et al, 2015;Y. Liu et al, 2023;Shen et al, 2016;X. Yang et al, 2023;Zhang et al, 2020).…”