Assessment of seismic liquefaction hazard and ground response in subduction zone: A 1D non-linear effective stress approach

Abstract The Makran Subduction Zone (MSZ) represents a convergent plate boundary where the Arabian Plate is subducting beneath the Eurasian Plate. This study assessed liquefaction susceptibility and ground response in Gwadar region, located on the eastern side of MSZ. A comprehensive dataset of seismic records, compatible with Pakistan design code BCP: 2021 rock spectrum, was used as input motions at bedrock. A series of one-dimensional (ID) non-linear effective stress analyses (NL-ESA) was conducted using DEEPSOIL v7 numerical tool. The findings revealed that pore water pressure ratio (r u ) exceeded the threshold value for liquefaction onset (r u > 0.8) at various depths within the site profiles. A significant de-amplification of peak ground acceleration values was observed at liquefiable depths in soft soils. The liquefied stratum exhibited a non-linear response, with high shear strain values manifesting plastic deformations. A comparison of computed design spectra with code spectra revealed significant discrepancies. It is demonstrated that BCP: 2021 underestimated site amplification for site class D profiles in the 0.1 to 0.8 s period range, while overestimating it for site class E profiles across the entire period range up to 1.6 s. The findings will benefit infrastructure development in the region, particularly within the China-Pakistan Economic Corridor.