Semi-automated Identification of the 7.3 Mw Earthquake Source in Flores Sea from Gridded Multibeam Bathymetry Data
Ana Iffah Sabila (a*), Gabriella Alodia (b), Astyka Pamumpuni (c), Hendra Kurnia Febriawan (d), Dwi Haryanto (d), Poerbandono (b), Irwan Meilano (e)

a) Geodesy and Geomatics Study Programme, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung, Indonesia
*anasabila66[at]gmail.com
b) Hydrography Research Group, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung, Indonesia
c) Applied Geology Research Group, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung, Indonesia
d) Directorate of Research Vessel Management, National Innovation and Research Agency (BRIN), Jakarta, Indonesia
e) Surveying and Cadastre Research Group, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung, Indonesia

Abstract

On December 14th, 2021, a 7.3 Mw earthquake struck the Flores Sea followed by a 7 cm-high baby tsunami near the Flores Island. According to BMKG (Indonesian Meteorology, Climatology, and Geophysical Agency), the earthquake was caused by a strike-slip mechanism. By the year of occurrence, no strike-slip fault has been discovered within the Flores Sea area. This study aims to identify the geometric shape of a newly identified fault, recently termed as the Kalaotoa Fault, using a gridded multibeam bathymetry data from a hydrographic survey. The identification process is carried out using SWE (slope-weighted eccentricity), is a semi-automated geomorphometric tool to classify the terrain of seafloor based on the shape and directionality of the object of interest. The result of this study shows that the Kalaotoa Fault ruptured with approximately 96.76 km length. The multibeam bathymetry data also shows a potential relation between the Kalaotoa Fault and the Flores Back-Arc Thrust southeast of the study area.

Keywords: Geomorphometry, Earthquake, Fault Mapping, Slope-weighted Eccentricity, Multibeam Bathymetry, Flores Sea

Topic: Marine Hazard, and Coastal Protection