Stress Modeling and Active Tectonics in the Northwest Himalayan Region, India: Implications for Incomplete Ruptures of MHT and Seismic Hazard Assessment

Session: From Aseismic Deformation to Seismic Transient Detection, Location and Characterization [Poster]
Type: Poster
Date: 4/29/2020
Time: 08:00 AM
Room: Ballroom
Description: 

Seismic ruptures on the Main Himalayan Thrust (MHT) or detachment due to four major to moderate earthquakes of magnitude (Mw) ≥ 6.6 during 1905–2013 has investigated in terms of Coulomb stress evolution. The absence of surface expressions of earthquake ruptures on the detachment is due to the presence of heterogeneous patches of fossil strain. This seems to be dependent on the width of the interseismic decoupling transition zone, which depends on the local dip and depth of the decollement as indicated by our coulomb stress modeling. The positive coulomb stress on the detachment in this segment is consistent with tectonic loading over 109 yr., which we expect will lead to future earthquakes and associated seismic hazard in the western Himalaya.

The Seismic potential of the Himalayan segment (30-33°N; 76- 80°E) of the Northwest Himalayan, India has been estimated in order to evaluate the potential of seismic hazard in this region. The hypocentral parameters estimated incorporating the local crustal velocity model derived utilizing 20 seismic stations and relocated 462 earthquakes triggered in the NW Himalaya during 2004 and 2015. We have also determined moment tensor solutions for 9 (Mw>4.0) earthquakes using waveform inversion. The geometry of the MHT plane has also been deduced in this study which varies along the strike of the Himalaya in flat and ramp segments with a dip ranging from 4° to 19° below the HFT in the south to STD in the north. There are also two new crustal ramps reported in this study having a depth range from 10 to 22 km below the MCT (31.0°N, 77.5°E) and 30 to 40 km beneath the STD (32.2°N, 78.4°E) respectively. The earthquake potential prevailing in the western Himalayan seismic gap lying between the epicentral zone of the 1905 Kangra earthquake and the 1975 Kinnaur earthquake has also been estimated. The total amount of energy released since the last great event has estimated is only a fraction (3-5%) of the accumulated total energy (95-98%). This indicates that the energy stored in this region can generate in future an earthquake of Mw > 8.0.

Presenting Author: Sushil Kumar

Authors