Tectonic and tsunami characteristics of Banda and Seram Seas: identifying tsunami-prone villages

Abstract The Banda and Seram Seas, located in the eastern part of Indonesia, have experienced numerous tsunamis due to their complex tectonic setting. Seismic activity in this region is primarily influenced by the megathrust along the 180° westward-bending Banda Arc, situated at the triple junction of the Eurasian, Indo-Australian, and Pacific Plates. This study evaluates the potential tsunami hazards associated with the nine segments of the Banda Arc using worst-case scenario tsunami modeling. The analysis is based on seismicity data recorded from 1960 to November 2023, historical tsunami events, and previous credible tectonic studies. The results of the tsunami modeling are further utilized to identify tsunami-prone villages that should be prioritized for tsunami preparedness programs. This study evaluates the seismic and tsunami hazards in the Banda and Seram Seas. Seismic assessments identify seven segments with the potential to generate significant shallow earthquakes (M ≥ 5) characterized by a thrust fault mechanism. Additionally, the Aru Interplate and Intraplate exhibit a shallow oblique normal fault mechanism. Tsunami modeling indicates that the Seram Interplate, Seram Intraplate, Babar Thrust, Tanimbar Megathrust, Wetar Back-Arc, and Weber Deep could generate substantial Estimated Tsunami Heights (ETH > 3 m), impacting 426 villages. In contrast, the Aru Interplate, Aru Intraplate, and Yamdena segments do not exhibit ETH exceeding 3 m. The most severe tsunami impact is associated with the Seram Thrust Fault Intraplate scenario (M8.6, depth 34 km), affecting Seram, Buru, Ambon, and surrounding islands, as well as the southern coast of the Banda Sea across a distance of more than 500 km. The maximum ETH recorded in this scenario is 24.6 m at Saunulu-Tehuru, Central Maluku. The findings underscore the need for disaster preparedness and mitigation strategies within this tectonically active region.