FE stress analysis and Quaternary deformation in the fold-and-thrust belt of the Garhwal Himalaya

The immense Himalayan arc is evolved as a consequence of the collision between Indian and Eurasian landmasses some 50 million year ago. The Indian plate converges northward at the average rate of 20.5 ± 2 mm/year (Bilham et al., 1988), and is under-thrusting beneath Tibet. This continuous northward penetration of India under Eurasia has produced the broad zone of active crustal deformation, shortening, slicing and surface uplift of the northern margin of the Indian continent; and build up the Himalaya is under very strong compressive strain that made the entire Himalayan region one of the most seismotectonically dynamic intercontinental regions of the world. In the present study, an approach has been made to model a NE-SW cross-section (Ram et al., 2005) extending from the Gangetic Plain to the Tethys Himalaya including potentially active major faults by means of FE method (Hayashi, 2008) considering an elastic rheology under plane strain condition with convergent boundary environment in the fold-and-thrust belt of the Garhwal Himalaya. The present study provides an opportunity to understand the neotectonic stress distribution, style of deformation and present day shortening rate in the Himalayan front. Simulation results reveal that the compressive stress of stress developed in the northern part and tensional stress fields developed in the southern part of the Garhwal Himalaya, and consequently, thrust are developed in the north and normal faults are developed in southern regions respectively, which is consistent with the characteristics of the fold and thrust belt. Furthermore, modeling results show good agreement with the Quaternary deformation, active faulting, microseismicity and focal mechanism solution of the fold-and-thrust belt of the Garhwal Himalaya.