<![CDATA[Background: Previous liquefaction studies along the West Sumatera coast have mainly focused on the Padang urban area and have relied on triggering analysis using CSR–CRR. However, post-liquefaction ground deformation, which can affect coastal defense infrastructure, has received limited attention. This study addresses this gap by combining CPT-based liquefaction analysis with finite element modelling to estimate post-liquefaction ground settlement in the southern coastal segment. The results provide a quantitative basis for assessing liquefaction-induced deformation and supporting coastal infrastructure design in this earthquake-prone area. Aims: Liquefaction is a major geotechnical hazard in coastal areas exposed to strong earthquakes, especially where loose and saturated sandy soils are present. The southern coast of West Sumatera is vulnerable to earthquake-induced liquefaction due to its proximity to the active Sunda megathrust. This study evaluates the liquefaction potential of coastal soils using Cone Penetration Test (CPT)-based analysis under different seismic loading conditions. Three CPT points were analyzed to characterize the subsurface soil and assess its liquefaction susceptibility. Method: The liquefaction assessment compared the Cyclic Stress Ratio (CSR) from earthquake loading with the Cyclic Resistance Ratio (CRR) from CPT data. Peak ground accelerations of 0.15 g, 0.28 g, and 0.60 g were used to represent low, moderate, and strong earthquakes. The factor of safety (SF) was then calculated to identify soil layers susceptible to liquefaction. In addition, PLAXIS 2D was used to simulate post-liquefaction behavior using the Mohr–Coulomb model and CPT-based soil parameters, with the groundwater table set at 1.5 m depth. The analysis focused on the relationship between liquefaction resistance and post-liquefaction volumetric strain. Result: The results show that liquefaction susceptibility increases with seismic intensity. At 0.15 g, most soil layers have SF values above 1.0 (1.2–3.8), indicating stable conditions. At 0.28 g, some layers at depths of 6–10 m become marginally unstable. At 0.60 g, most layers between 3 and 15 m have SF values below 1.0, indicating high liquefaction potential. The finite element results also show an inverse relationship between safety factors and volumetric strain ( ), indicating that lower liquefaction resistance leads to greater post-liquefaction deformation. Conclusion: Overall, this study demonstrates that the investigated coastal deposits are highly vulnerable to strong earthquake loading and emphasizes the importance of liquefaction mitigation measures for infrastructure development in earthquake-prone coastal regions.]]>
