Lower Crustal Rheology Controls the Development of Large Offset Strike‐Slip Faults During the Himalayan‐Tibetan Orogeny
Jianfeng Yang, Boris Kaus, Yang Li, Philippe Hervé Leloup, Anton Popov, Gang Lü, Kun Wang, Liang Zhao
Abstract
Abstract The mechanism of crustal deformation and the development of large offset strike‐slip faults during continental collision, such as the India‐Eurasia zone, remains poorly understood. Previous mechanical models were simplified which are either (quasi‐)2‐D approximations or made the a priori assumption that the rheology of the lithosphere was either purely viscous (distributed deformation) or purely localized. Here we present three‐dimensional visco‐elasto‐plastic thermo‐mechanical simulations, which can produce both distributed and highly localized deformation, to investigate crustal deformation during continental indentation. Our results show that large‐scale shear zones develop as a result of frictional plasticity, which have many similarities with observed shear zones. Yet localized deformation requires both a strong upper crust (>10 22 Pa·s) and a moderately weak middle/lower crust (~10 20 Pa·s) in Tibet. The brittle shear zones in our models develop low viscosity zones directly beneath them, consistent with geological observations of exhumed faults, and geophysical observations across active faults.