Physics-based simulations of earthquake scenarios on the Kopili fault in Northeast India: Insights into seismic hazard and fault mechanics

Abstract

Understanding the seismic risks associated with the Kopili fault (KF) in northeast India is essential for effective risk management. We employed advanced physics-based dynamic rupture simulation scenarios to quantify the fault’s potential for generating damaging earthquakes. Our models indicate that the central KF segment can produce significant earthquakes with moment magnitudes (Mw) potentially reaching 7.3, and possibly up to 7.5. The analysis revealed considerable variability in rupture extent and ground motion characteristics, strongly influenced by fault and model parameters. A detailed stress inversion analysis shows that the maximum horizontal stress ($S_{\text{H}}$) is oriented at $\sim$N41°E within an oblique-reverse stress regime, significantly impacting rupture behavior. Rupture simulations indicate that earthquakes originating from the central segment of the fault produce the largest rupture areas and the most intense ground shaking, with peak ground velocities exceeding 0.6 m/s and corresponding intensities of MMI VIII and above. Sensitivity analyses highlight the critical roles of nucleation points, dynamic rupture parameters and $S_{\text{H}}$ orientation in determining rupture propagation and ground motion distribution. Notably, minor adjustments in $S_{\text{H}}$, such as a 10° variation, can lead to substantial changes in rupture characteristics, including extreme scenarios reaching Mw 7.5 in the counterclockwise stress rotation. Additionally, supershear effects observed in several scenarios likely stem from initial stress variations along the fault. The physics-based simulation of ground motion shows that, compared to ground motion prediction equations (GMPEs) estimates, it provides more reliable predictions. These insights enhance our understanding of how these parameters influence earthquake dynamics and are vital for developing effective earthquake risk management strategies in northeast India. By integrating physics-based dynamic rupture modeling with empirical ground motion predictions, our study could provide a robust framework for seismic hazard assessment in the KF zone and similar tectonic settings.