VULNERABILITY ANALYSIS OF EARTHQUAKE HAZARDS IN TASIKMALAYA CITY USING HORIZONTAL TO VERTICAL SPECTRAL RATIO (HVSR) METHOD

• Main Author: Insyirah Lianza Bakri, Najla
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/53160
• Institution: Institut Teknologi Bandung

Tasikmalaya City is one of the regions in West Java Province that is often hit by earthquakes. This is due to its location that close to the Indo-Australian Plate subduction zone towards the Eurasian Plate. The surface deposits in this city are alluvium and weakly consolidated step deposits which can cause wave amplification during an earthquake, so that the vibrations that are felt will be stronger. As an effort to mitigate the earthquake disaster in the City of Tasikmalaya, seismic zoning needs to be carried out to map the areas that will experience heavy damage when an earthquake occurs. This study uses the Horizontal to Vertical Spectral Ratio (HVSR) method which is applied to the microtremor recording data to obtain spatial variations in the predominant frequency and amplification values that can explain the characteristics of the geological layer beneath the surface. Based on the obtained results, the predominant frequency ranging from 0.71 to 9.42 Hz with the lowest frequency distribution in the eastern, southeastern, and northwestern parts, which indicates a sediment layer that tends to be thicker. The range of amplification values are from 1.15 to 12.59 with the distribution of higher values in the eastern, southeastern, southern, and northwestern parts of the research area. The inversion of the HVSR curves was carried out to determine the value of shear wave velocity (????!) in order to obtain a more detailed subsurface geological structure that can be used to determine the level of vulnerability of earthquake hazards. The Neighborhood Algorithm is used to find an optimum model. Based on the results of the inversion process, the ????! ranging from 150 to 3054 m/s with lower ???? ! values in the eastern, southeastern, and northwestern parts at depth of about 25 meters. The average value of shear wave velocity at a depth of 30 meters (????!"#) can also be used to determine the type of soil for geotechnical study. From the obtained ????!"#data, the types of soil in the research area are classified into moderate soil, hard soil, and rocks.