The estimation of total vertical uncertainty from multibeam echosounder during MeGaMal Expedition seafloor mapping for earthquake mechanism at Maluku Sea.

Abstract In 2022, the Indonesian government initiated the EWIN MeGaMal expedition (Ekspedisi Widya Nusantara Mekanisme Gempa Laut Maluku). The goal of the expedition is to map earthquake and tsunamigenic potential areas around Ambon Island. The expedition was carried out from 8 to 28 August 2022 using RV Baruna Jaya VIII. One of the methods used in the expedition is the multibeam echosounder (MBES) survey. To obtain an accurate bathymetry result, several stages need to be carried out. Initially, a vessel reference frame (VRF) with a defined reference point called common reference point (CRP) needs to be established. Then, sensor offsets in 3D (three-dimensional) is measured with respect to CRP. The next stage is to calibrate and validate the vessel’s differential global navigation satellite system (D-GNSS) and Heading system statically. Afterwards, a patch test dynamic MBES calibration is performed. Finally, the accuracy of the bathymetry result is analyzed in accordance with the International Hydrographic Organization (IHO) SP 44. This paper is aimed to describe each of the above methodologies and present the preliminary result. Results show that the Patch Test calibration has values of roll : -0.19°, pitc h: -5.40°, and yaw : 1.09°. It is expected this expedition could contribute for mitigation of earthquakes and tsunamis in Eastern Indonesia.