The Makran Subduction Zone in Iran and Pakistan: A Review of Tectonics and Seismic Hazards

Abstract

The Makran Subduction Zone (MSZ) in southeastern Iran and Pakistan is a tectonically segmented convergent margin where the Arabian Plate subducts beneath the Eurasian Plate. Analysis of recent geological, geophysical, and seismological datasets reveals that the eastern and western segments differ fundamentally in slab geometry, coupling strength, and seismic behavior, which jointly control the spatial distribution of seismic hazards. The eastern segment, with higher plate coupling and a shallow subduction angle (~8◦), predominantly accumulates elastic strain and is capable of generating abrupt megathrust ruptures, as evidenced by the Mw 8.1 event of 1945. In contrast, the western segment, characterized by a steeper subduction angle (~30◦), reduced coupling, and sediment-saturated plate interfaces, accommodates strain mainly through aseismic slip and mechanical decoupling, thereby limiting the potential for large megathrust earthquakes but increasing the likelihood of intraplate and upper-plate seismicity. Stress tensor inversions and b-value distributions indicate heterogeneous stress regimes along strike, reflecting variations in lithospheric architecture, slab metamorphism, and fluid-related processes. These findings underscore the necessity of integrating high-resolution seismic imaging (e.g., tomography, InSAR, MT), long-term seismic monitoring, and advanced numerical modeling to constrain fault segmentation, strain partitioning, and hazard potential. Overall, the MSZ represents a distinctly segmented subduction system, where contrasting rheological and structural domains demand segment-specific probabilistic hazard assessments and tailored risk mitigation strategies.