Crustal Thickness and Poisson's Ratio in the Pamir–West Tianshan Region

Abstract

Crustal thickness and Poisson's ratio are key indicators of regional isostasy and material composition. Using teleseismic waveform data from 126 permanent stations and 179 temporary stations in the Pamir–West Tianshan region, we obtain the crustal thickness and average Poisson's ratio by the h–κ stacking method. The results show that the crust of the Pamir Plateau is thick in the middle and thin on its eastern and western sides, while the West Tianshan region exhibits a “thin–thick–thin” distribution from south to north. The mountainous regions have thicker crust compared to the intermountain basins which feature relatively thinner crust in West Tianshan. Based on the isostasy state analysis of the Airy model, the equilibrium curves of the Pamir and the West Tianshan are similar. The distribution of Poisson's ratio in the study area is characterized by several east–west oriented bands, forming a “high–low–high” distribution pattern as a whole. Joint geophysical and geochemical studies indicate that regions with high Poisson's ratio often have phenomena such as lithospheric subduction and Moho offsets, these areas also display characteristics such as low velocity, high conductivity, and high surface heat flow, which may be related to local melting materials in the middle and lower crust.

Keywords

crustal thickness / local melting / h–κ stacking / Poisson's ratio / Pamir–West Tianshan

RIGHTS & PERMISSIONS

2025 Geological Society of China