Analysis of Local Footprint Effects Due to the Lombok Earthquake in July-August 2018 in Labuapi District, West Lombok Regency

Abstract

Lombok island is one of the areas prone to earthquakes. In 2018 an earthquake occurred which caused most of the regions in Lombok to experience its effects, one of which was in Labuapi District. This study aims to analyze the characteristics of local footprint effects based on frequency and amplification values ​​using the Horizontal to Vertical Spectral Ratio (HVSR) method and seismic vulnerability index (Kg), Vs30, and Peak Ground Acceleration (PGA) methods. The structure of the coating on the research area has a relatively low frequency value of 0.6 Hz – 12 Hz, with variations of amplification factors between 1 – 11. Seismic vulnerability index (Kg) variation ranges from 0.25 - 150, which illustrates the study area has a relatively high level of vulnerability. The Vs30 value in the study area was found to be relatively low at 240 m/s - 262 m/s, while the PGA values ​​obtained ranged between 160 cm/s² -760 cm/s². By looking at the results of the correlation between measurement data with damage data that shows that damage to the study area is more dominantly influenced by building structures.