Tsunami hazard assessment in the Persian Gulf: Evaluating near-field and far-field sources

Abstract

Despite the relatively low probability of tsunamis in the Persian Gulf, the region's strategic importance necessitate a comprehensive risk assessment. This study evaluates both near-field and far-field tsunami sources affecting the Persian Gulf using numerical modeling based on nonlinear shallow-water equations. The Kazerun Fault system, recently identified as extending into the Gulf, is analyzed as a local tsunami source, while the maximum probable earthquake of the Makran subduction zone is considered the primary distant threat. Bathymetric influences are assessed by simulating near-field scenarios with both actual depth data and artificially deepened basin configurations.

Simulations reveal that for an Mw 7.9 earthquake, pure thrust faulting along the Kazerun Fault generates a tsunami with wave heights of up to 3 m, whereas purely strike-slip mechanisms yield negligible amplitudes (<0.3 m). While most coastal zones under actual bathymetry exhibit lower wave heights than deepened scenarios, localized areas show comparable or greater amplitudes. These findings challenge the assumption that shallow bathymetry inherently limits tsunami impacts in the Persian Gulf, demonstrating that depth-related attenuation alone cannot ensure immunity. Far-field modeling indicates that, despite precise modeling using nested bathymetry grids and accounting for non-uniform slip distributions to capture worst-case scenarios, Makran tsunami waves entering the Persian Gulf remain below 0.5 m, aligning with prior studies. This suggests that the Gulf's interior shores are largely protected against tsunamis originating from the Makran subduction zone. However, this work underscores the necessity of reevaluating local tsunami sources, particularly the offshore segments of the Kazerun Fault.