Stress distribution and seismic faulting in the Nepal Himalaya : insights from finite element modeling

概要

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In this study we use 2D finite element modeling to predict stress distribution and fault development during N-S shorting in the Himalayas. The direction of maximum compressive stress (σ_1) is horizontal within the shallow levels of both models. Variation in the displacement boundary conditions results in changes of principal stress directions in the deep crust while stresses in the shallow crust remain unchanged. Mohr-Coulomb failure is observed along near-surface sections of the Siwalik, Tethys and Granitic basement layers, with minor failure near the surface of the MBT, MCT and STDS. Failure does not occur due to hydrostatic conditions in the deeper part of the Higher Himalaya, the Lesser Himalaya or the Granitic basement layer, despite changing the rheology of rock layers. Focal mechanism solutions of earthquakes in the Himalayan region suggest the existence of thrust faults stretching along EW with one plane dipping gently north beneath the Himalaya. The simulations predict a similar distribution of thrust faults along the upper part of the Himalaya.
構造地質研究会の論文