PROBABILISTIC SEISMIC HAZARD ASSESSMENT OF THE POTWAR PLATEAU AND SALT RANGE REGION USING R-CRISIS

Abstract

The Khewra Salt Mine, located within the seismically active Salt Range and Potwar Plateau region of Pakistan, is a critical industrial and tourist site situated near the convergence of major thrust and strike-slip fault systems. Despite its structural significance, no site-specific probabilistic seismic hazard assessment has previously been conducted for this facility. This study performs a rigorous Probabilistic Seismic Hazard Analysis (PSHA) of the Khewra Salt Mine and surrounding region using the R-CRISIS software platform, following Cornell-McGuire methodology. Four primary seismogenic sources are modeled: the Salt Range Thrust (SRT), Main Boundary Thrust (MBT), Jhelum Fault (JF), and Kalabagh Fault (KF), with seismicity parameters derived from regional earthquake catalogs and structural literature. The Bounded Gutenberg-Richter recurrence model is employed with a uniform threshold magnitude of M₀ = 4.5, and ground motion attenuation is characterized using the Akkar et al. Next Generation Attenuation model. A 300 km integration radius and a computation grid of 3,575 target points are used to generate high-resolution Peak Ground Acceleration (PGA) hazard contour maps. Results indicate that PGA values across the study area range from 0.00g to 0.23g, with both the Khewra Salt Mine and the Civil Hospital Khewra falling within a moderate hazard zone of 0.06g to 0.12g. A five-tier seismic zonation scheme is developed to support risk-informed infrastructure planning. The findings provide baseline design parameters for underground structural reinforcement, healthcare facility retrofitting, and regional disaster preparedness frameworks.