SOIL DYNAMIC RESPONSE MAPPING AND Vs STRUCTURAL IMAGING USING HVSR METHOD FROM MICROTREMOR DATA IN PALU CITY

• Main Author: Widia Pamungkas I., Rosliani
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/43766
• Institution: Institut Teknologi Bandung

Palu City is one of the cities on the island of Sulawesi with a very complex geology. There are many active faults on Sulawesi Island, one of which is the Palu Koro Fault. If there is thick sediment under Palu City, the sediment can cause amplification of the soil during an earthquake so that the damage caused will be quite severe. In order to characterize the subsurface structure of the City of Palu, microtremor data processing was carried out from 22 stations using the Horizontalto-Vertical Spectral Ratio (HVSR) method. HVSR is a method for obtaining subsurface information from a single station measurement that can be used to examine seismic risk. HVSR is done by comparing the Fourier spectrum of horizontal components with vertical components. This ratio is a function of the frequency that will produce the H/V curve. From the H/V curve, dominant frequency and amplification can be mapped. The map shows that in the area around Palu Bay the dominant frequency is low and amplification is high. The mapped H/V curve is then inversed with the PSO algorithm to get the subsurface structure based on its shear velocity. PSO or Particle Swarm Optimization is a global optimization algorithm that it is based on the behavior of the individuals in groups in nature. The inversion results show that there is a low-velocity structure that forms a basin below the surface of Palu City in the north and southeast of Palu.