Effective elastic thickness of the lithosphere from joint inversion in western China and its implications*

Abstract

The western China lies in the convergence zone between Eurasian and Indian plates. It is an ideal place to study the lithosphere dynamics and tectonic evolutions on the continental Earth. The lithospheric strength is a key factor in controlling the lithosphere dynamics and deformations. The effective elastic thickness (Te) of the lithosphere can be used to address the lithospheric strength. Previous researchers only used one of the admittance or coherence methods to investigate the Te in the western China. Moreover, most of them ignored the internal loads of the lithosphere during the Te calculation, which can produce large biases in the Te estimations. To provide more reliable Te estimations, we used a new joint inversion method that integrated both admittance and coherence techniques to compute the Te in this study, with the WGM2012 gravity data, the ETOPO1 topographic data, and the Moho depths from the CRUST1.0 model. The internal loads are considered and investigated using the load ratio (F). Our results show that the joint inversion method can yield reliable Te and F values. Based on the analysis of Te and F distributions, we suggest (1) the northern Tibetan Plateau could be the front edge of the plate collision of Eurasian and Indian plates; (2) the southern and part of central Tibetan Plateau have a strong lithospheric mantle related to the rigid underthrusting Indian plate; (3) the southeastern Tibetan Plateau may be experiencing the delamination of lithosphere and upwelling of asthenosphere.