Interseismic fault kinematics along the Kumaun Himalaya: Insights from InSAR and GPS based observations

Abstract

Long-term seismic activity along the Main Himalayan Thrust (MHT) raises significant concern for the Kumaun Himalaya. Using the most updated high-resolution integrated velocity field based on InSAR and GPS observations, the present study aims to provide spatial distribution of interseismic slip rates and fault geometry of MHT in the Kumaun region. Results through the Bayesian inversion framework reveal several key features of fault behavior: dip angles range between 28.2$°$ and 34.2$°$, with locking depths of approximately 6.7$\pm$0.7 km to 9.9$\pm$0.2 km, and fault depths around 12.9$\pm$0.4 km. The transition zone from locked to creeping portion displays slip rates of 1.7$\pm$0.6 mm/yr to 1.9$\pm$0.9 mm/yr. Estimated long-term slip rate of the MHT is 19.7$\pm$0.2 mm/yr, with a slip deficit rate of 18.0 mm/yr. The estimated moment deficit rate is approximately $5.40\times 10^{18}$ Nm/yr, which suggests the potential for a great earthquake of magnitude $M_w$ 8.3, assuming a seismic cycle of $\sim$500 years. Thus, the estimated slip deficit from the integrated velocity field highlights significant seismic hazards in the locked segments of the MHT. Overall, the findings provide crucial inputs for seismic risk assessment and mitigation efforts in the Kumaun Himalaya.