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High-Resolution Crustal Attenuation Model in Southeastern Tibetan Plateau and Its Implications for Regional Tectonic Deformation

Description: 

The ongoing continental collision between the Indian and Eurasian plates since ~ 55 Ma led to the uplift of the Tibetan Plateau, which shortens and thickens in the north-south direction and expands towards its southeast and northeast margins (Holt et al., 1991; Zhang et al., 2004). In southeastern Tibet, the growth and deformation mechanism of the plateau has become the focus of attention. Some classical models have been proposed to explain the dynamic mechanism of the tectonic evolution of the Tibetan Plateau, such as the “rigid-block extrusion” model (Molnar and Tapponnier, 1975), the “mid-lower crustal channel flow” model (Royden et al., 1997), and the combination model of these two end-member models proposed in recent years (Liu et al., 2014; Bao et al., 2015; Qiao et al., 2018; He et al., 2021), etc. How to select these models and determine the tectonic deformation mode of the southeast margin of the Tibetan Plateau remains controversial.

The quality factor Q of seismic wave attenuation is more sensitive to temperature, partial melting and fluid content of the underground media than seismic wave velocity (Amalokwu et al., 2014; Winkler & Nur, 1982), thereby can be a useful indicator of potential crustal material escape. In this study, we use the seismic Pg-wave attenuation tomography method to construct the high-resolution broadband Q_Pg model for the crust in the southeastern Tibet and provide new constraints. Our result reveals two independent weak zones in the crust of the southeast margin of the Tibetan Plateau. The strong attenuation in Western Sichuan block and Songpan-Ganzi block may serve as the mid-lower crustal flow channel, with partial melting or aqueous fluids. The crustal ductile flow was blocked by the Emeishan Large Igneous Province and did not enter the foreland Yangtze Craton. The relatively weak zone under the Xiaojiang fault is likely related to the heating effect of the asthenospheric upwelling. This research was funded by the National Natural Science Foundation of China (U2139206, 41974061, 41974054) and the Special Fund of China Seismic Experimental Site (2019CSES0103).

Session: Earth’s Structure From the Crust to the Core

Type: Oral

Date: 4/18/2023

Presentation Time: 08:30 AM (local time)

Presenting Author: Ruo-Jie Li

Student Presenter: Yes

Invited Presentation: 

Authors