The Pattern and Possible Formation Mechanisms of Current Crustal Stress in High Asia

Abstract

Abstract —The pattern of current crustal stress in central and southeastern Asia has been reconstructed from earthquake focal mechanisms by inversion using Rebetsky’s method of cataclastic analysis. The inversion provides constraints on principal stress directions, as well as on relative magnitudes of maximum shear and effective isotropic pressure. The crust of the High Asian mountainous province is subject to horizontal extension or shear in plateaus (East and South Pamir and Tibet) and to horizontal compression or shear in mountain ranges. The relatively high horizontal compression in the ranges is apparently due more to denudation and exhumation than to the pressure from the Indian indentor. Denudation and removal of clastic material from the Himalayan slopes has been a key agent that may compensate for the N–S crust shortening in central Tibet and the W–E stretching in eastern Tibet. The current stress field of High Asia has been mainly controlled by vertical buoyancy forces that arise by thickening of lighter crust and detachment of heavier lithosphere.