A site-specific earthquake ground response analysis and relations to collapsing buildings in the 2021 Mw. 6.2 Mamuju-Majene Earthquake Sulawesi Indonesia

抄録

Sulawesi is a large island of Indonesia's archipelago which has experienced major earthquakes. On January 15th, 2021, West Sulawesi was struck by a shallow earthquake Mw 6.2 at 02:28:21 local time. Thousands of structures collapsed and suffered serious damage as a result of the earthquake, killing hundreds of people. Mamuju's seismicity is poorly understood, and the studies that have been done on it have only covered a small portion of it. As a result, the objective of this research is to determine how the city's local geology and soil conditions affect the intensity of ground motion, which is measured in terms of its amplitude, frequency, and duration, and how these factors relate to the city's damaged buildings as a result of the 2021 Earthquake. Therefore, a series of geotechnical drillings consisting of borehole-N SPT measurements were undertaken on the studied area in the city. Shear wave velocity profiles of the ground were derived through MASW measurements. Time histories of the 2021 Mamuju Earthquake were derived from the data of Indonesia’s geophysical agency (BMKG). Site-specific ground response analysis was conducted within equivalent elastic linear (EL) approaches to model ground time histories in the 2021 Mamuju Earthquake. A non-linear time histories FEM modeling of typical structures in the city within three stories buildings was undertaken based on generated ground time histories of the 2021 Mamuju Earthquake. The seismic amplification in the earthquake event and its relation to the numerous cases of buildings collapsing was evaluated. The results of this study reveal that typical ground in the city has a resonance frequency of 0.5 –0.8 Hz, with an amplification factor of 2.3. This seismic amplification has resulted in structural consequences in the typical RC building in Mamuju, in which several columns in the 2^nd and 3^rd stories have beam-column capacity ratios exceeding 1.00. The results may indicate the high case of buildings collapsed during the 2021 Mamuju – Majene Earthquake.