SPT-based deterministic assessment of soil liquefaction susceptibility in North Sumatra, Indonesia

Abstract

North Sumatra faces significant seismic threats from the Sumatran fault zone and the subduction zone, both of which can compromise infrastructure stability through soil liquefaction. This study aims to evaluate liquefaction susceptibility across eight strategic locations in North Sumatra using a high-resolution deterministic approach. The research methodology is based on a simplified procedure employing the standard penetration test (SPT) to determine the factor of safety (FS) against liquefaction. Seismic parameters were calculated using peak ground acceleration (PGA) and moment magnitude (Mw) data obtained from the Indonesian Research and Development Center for Human Settlements (Puskim). The analysis incorporates the cyclic stress ratio (CSR) to represent seismic demand and the cyclic resistance ratio (CRR) to represent soil capacity, with adjustments for the magnitude scaling factor (MSF) and fines content (FC). The results indicate critical vulnerability at several sites, particularly in Sibolga and Mandailing Natal, where the FS value is less than 1.0 at depths between 2 and 10 meters. In contrast, locations with denser sandy layers and lower groundwater levels exhibit greater stability. These findings provide an important deterministic baseline for seismic hazard mitigation and geotechnical design in disaster-prone regions of Indonesia.