Tectonic stress regime and stress patterns from the inversion of earthquake focal mechanisms in NW Himalaya and surrounding regions

Abstract

Because the impact of earthquake effects can extend over great distances from their origin, stress field inversion was performed for 440 earthquake focal mechanisms from the northwest Himalayas and surrounding regions compiled from the data bulletins of international seismological institutions. Earthquakes between November 1976 and April 2019 in the depth range of 10–258 km with moment magnitudes between 4.6 and 7.9 were selected. High-quality solutions were inverted to locate the best fitting stress tensor. Most of the earthquake fault plane solutions indicated thrust faulting, confirming northward underthrusting of the Indian plate along the Main Boundary Thrust and the Main Central Thrust systems and eastward underthrusting along the Burmese Arc. The focal mechanisms indicated right-lateral motion along the Karakoram Fault and left-lateral motion along the Kirthar–Sulaiman Range, which agrees with the expected sense of the lateral mass movement of the continental collision model. The present-day stress regimes obtained from the earthquake focal mechanism inversions indicated a predominantly compressional stress regime represented by NNE–SSW trending normal fault mechanisms in northwest India and Nepal and NNW–SSE trending normal fault mechanisms in Pakistan and Hindukush. These are consistent with the direction of the ongoing India–Eurasia plate collision and the extensional stress of WNW–ESE trending thrust faulting in the Xizang and Kashmir regions. These tectonic regimes connected with the major tectonic affecting the Arabian Peninsula. Accordingly, it is highly recommended to assess the earthquake hazards of the major cities in the eastern countries of Arabian Peninsula as Kuwait, Saudi Arabia, United Arab Emirates and Oman.