Application of HVSR Method for Evaluating Seismicall-Induced Slope Instability Potential in Sukorejo Village, Pugung District, Tanggamus Regency, Indonesia

Abstract

This study investigates HVSR parameters, predominant frequency (Fo), amplification factor (Ao), shear strain, and seismic vulnerability index (Kg) to evaluate their relation to local geology, morphology, and earthquake-induced landslide potential in the hilly region of Tanggamus. The results show that areas with high amplification values (>12), particularly in the F3–E3 to D5 zones, experience significant strengthening of seismic waves within the upper soil layers. These zones also exhibit low predominant frequencies (2–8 Hz), indicating thick sedimentary deposits with strong impedance contrast that tend to resonate at low frequencies, especially on long slopes and inter-hill valleys. Increased shear strain values (>0.15) suggest soft, unconsolidated, and water-saturated soils that are easily deformed during seismic shaking, increasing their susceptibility to failure. The seismic vulnerability index (Kg) reaches its highest levels (>1200) in the same areas, reflecting the combined effect of thick sediments, strong amplification, and low-frequency resonance. Geological analysis shows that highly vulnerable zones correspond to the Hulusimpang Formation (Tomh), characterized by weak sedimentary materials, while more stable regions underlain by the Gunungkasih Complex (Pzg) display lower HVSR parameter values. Overall, the F3–E3–D5 zone is classified as the most susceptible to earthquake-triggered landslides, the D3–F4–H3 zone as moderate