Hypocenter Relocation of Local Earthquake using Double Difference Method in Central Sulawesi from BMKG Network Data: Time Periods of July 26 - August 18, 2021

Abstract

Last July 2021, a destructive earthquake occurred in the northern Ampana area, Central Sulawesi, with the epicenter at sea. We investigated the earthquake and found 101 hypocenter points with a magnitude of 2-6 Mw from 26 July to 18 August 2021 using the BMKG network. Of the 101 earthquakes, we relocated the hypocenter using the multiple difference method and obtained 75 earthquake events resulting from the relocation. The results obtained from the relocation are that several earthquake events with a fixed depth of 10 km have been updated. To validate the results, we used a histogram of travel time results, which depict the relocation results as good, and some close to zero. The results of the hypocenter relocation have a depth of 5 to 30 km and are collected in one location. The shift’s direction and angle from the relocation results show that most of them are in a dominant direction to the north. It is interpreted that the earthquake was caused by force activity caused by the Balantak thrust, which is in the east and has a north direction towards the study site.

Analyzing Seismicity Pattern of the Gorontalo Region and Its Surroundings in the Form of Hypocenter Relocation Using Double Difference Method

“…The seismicity value is measured by reviewing the condition of the level of seismic activity between regions, which is also one of the most important parameters to measure a region's seismicity level. (Apandi & Bachri, 1997;S Bachri et al, 1993) Hypocenter relocation is very important in order to get the seismicity condition of an area accurately so that it can be better in analyzing its tectonic order, as has been done by (Efendi et al, 2021;Gusman et al, 2017;Jayadi et al, 2023;Syafriani et al, 2023). The purpose of this study is to analyze the level of seismicity of the Gorontalo region and its surroundings based on data from the relocation of earthquake hypocenters so that it can be used to understand better and provide more accurate information in reconstructing seismic activity and tectonic order conditions that are closely related to regional geological conditions to mitigate geological natural disasters, especially earthquakes and for development planning in the Gorontalo region and its surroundings.…”