DefinePK

Abstract

Local geology condition has become one of the most parameters which affected damage level of earthquake. Local geology condition can be analysed based on the value of Seismic Vulnerability Index (Kg). The areas with high vulnerability index is estimated to have high probability of deformation an earthquake happened. Seismic vulnerability index of Bengkulu city has obtained by horizontal vertical spectral ratio (HVSR) analysis of sixty-seven micro-tremor recordings data that was installed on each geology formation types. Based on analysis result show that the seismic vulnerability index of Bengkulu city relatively heterogeneous in spite of on similar geology type. This variation was influenced by the thickness of sediment layer and the violence level of ground on the site. In general, the highest Kg value is on the alluvium terraces (Qat) about 0.01-10.26 and the lowest Kg value is on Reef Limestone (Ql) about 0.05-0.35. Distribution of seismic vulnerability index has compatibility with the soil surface condition visually. The highest Kg value of Bengkulu city was only obtained on alluvium terraces which was estimated to have softer structure (visual observation showed the former swamp), and it had thicker sediment layer (based on f0 value) than the other type of geology. This result showed that alluvium terraces has higher probability of deformation when an earthquake than others, such as the occurrence of high resonance effect, the strengthening of earthquake vibration and liquefaction. The safest area in Bengkulu city was identified on Andesit (Tpan) geology formation type.