Deformational pattern and seismogenic potential of the eastern Makran subduction zone

Abstract

• The Makran subduction zone has an imbricate thrust fault system. • Attribute analyses show Makran turbidities are fractured under high pore pressures . • Lateral continuity is observed in the frontal region via velocity analysis. • Effective friction 0.04–0.12 is required to reproduce the observed fault system. • Splay faults with high uplift values can amplify earthquake related tsunami. In last 500 years, the ∼900 km long Makran subduction zone (MSZ) has hosted 9 M7+ large earthquakes, and 8 of them activated the eastern segment of the fault. The 1945 M 8.1 megathrust event also generated significant tsunami signifying the region as active subduction zone in the world. Here, we investigate the deformation patterns and seismogenic potential of MSZ utilizing detailed seismic data analyses. Mechanical modeling based on limit analysis approach has also been applied to better understand the seismic shaking potential of ongoing deformation and retrieve the associated frictional properties. The seismic structural interpretation illustrates that MSZ has an imbricate thrust fault system. Furthermore, seismic attributes highlight the fractured and high porosity zones, which reduce friction values along the plate interface. The estimated effective friction ( μ e f f ) to slip does not exceed 0.12 along the subduction interface. We found that μ e f f ∼ 0.04–0.12 is required to reproduce the observed fault system. For wedge geometry, we run different simulations to measure the frontal horizontal and vertical slip. Assuming the convergence rate of 3–4 cm/yr, the calculated slip deficit in last 77, 158, and 257 years, after 1945, 1864 and 1765 earthquakes along offshore-ruptured patches of eastern MSZ is 2.31–3.08 m, 4.74–6.32 m, and 7.71–10.28 m, respectively. A frontal uplift ranging from 0.69 ± 0.37 to 3.02 ± 1.45 m can be expected, if the next rupture occurs along the previously ruptured areas, which possess the ability to amplify the water column and generate a large tsunami in the region.