MICROTREMOR MEASUREMENT AT LIQUEFACTION-INDUCED GROUND DEFORMATION AREA

Liquefaction has caused significant structural failures worldwide, including Indonesia since the liquefaction-induced ground displacement has occurred at the Petobo area during the 2018 Palu earthquake. The manifestation of liquefaction on the ground surface is also still under research scrutiny. Liquefiable soils are cohesionless and loose particulate materials, which are very difficult to sample, hence in-situ testing of microtremor measurement is preferred in this study. This study is aimed to investigate the effectiveness of microtremor method for liquefaction assessment and to examine the characteristics of the measured site. To fulfill these aims, a seismometer was deployed to the devastated site of liquefaction-induced ground deformations at the Petobo area. Fourteen ambient noise measurements were collected and analyzed using horizontal to vertical spectral ratio (HVSR) and neighborhood algorithm (NA). The HVSR analysis suggests that the predominant frequency of the study site is between 0.97 Hz to 1.67 Hz. The NA inversion suggests that the critical layer to liquefy is the top 4 to 6 m. A further examination of the results was carried out by comparing the results of this study to other studies. This examination suggests the effectiveness of the applied method of this study for quick disaster response in liquefaction assessment.