Study of seismic vulnerability index (Kg) from dominant frequency (f<inf>0</inf>) and amplification factor (A<inf>0</inf>) by means of microzonation data: Case study on Batubesi dam of Nuha, East Luwu, South Sulawesi, Indonesia

Abstract

Study of seismic vulnerability index (Kg) from dominant frequency (f 0 ) and amplification factor (A0) by means of microzonation data has been carried out. The study was conducted to obtain a map of the dominant frequency (f 0 ), the dominant period (T 0 ), and the amplification factor (A0). It was conducted in Batubesi dam of Nuha — East Luwu — South Sulawesi — Indonesia which is located at the coordinates of 2.71428°–2.70585°S and 121.3013°–121.3117°E. This research is expected to obtain spatial distribution of the dominant frequency (f0), the dominant period (T0), the amplification factor (A0), and the seismic vulnerability index (Kg). The Nakamura method was used in order to obtain the dominant frequency (f0) and amplification factor (A0) values. The spectral ratio between the vertical and horizontal components (H/V) of the HVSR analysis was used to estimate the dominant frequency (f0). The seismic vulnerability index (Kg) was obtained from the dominant frequency (f0) and amplification factor (A0) values which were used to estimate the earthquake hazards potential on the location. Based on the data results, the f0min is 0.59 Hz at the point of MSBB25, the f0max is 13.7 Hz at the point of MSBB21, the A0min is 1.35 at the point of MSBB22, the A0max is 11.5 at the point of MSBB10, the T0min is 0.07 s at the point of MSBB21, the T0max is 1.69 s at the point of MSBB25, the Kgmin is 0.28 at the point of MSBB22, and the Kgmax is 33.42 at the point of MSBB10. Based on the dominant period (T0), amplification factor (A0), and seismic vulnerability index (Kg), it can be estimated that the soil classification for Kanai model is in the range of II–IV and in the range of B–C for Omote-Nakajima model.