An initial assessment of volcanic meteo-tsunamis hazard in the South China Sea shows considerable bathymetric effects

Volcanic meteo-tsunamis, though rare, can pose significant threats to people, as exemplified by the 2022 Hunga Tonga – Hunga Ha’apai (HT-HH) eruption in the SW Pacific. While various studies have delved into the complexities of such phenomena, none have explored analogous scenarios in regions with potential occurrence of large eruptions near or under the sea. We focus on coastal areas along the South China Sea (SCS), among the most densely populated on Earth and historically prone to volcanic activity, including the catastrophic 1883 Krakatau eruption. Here we strategically chose one intra-basin volcano, KW-23612 in the northern SCS, and three extra-basin volcanoes, Banua Wuhu in the Celebes Sea, and Kikai and Fukutoku-Oka-no-Ba in the northern Philippines Sea (southern Japan), from which we simulated volcanic meteo-tsunamis with scaled intensities of the HT-HH event, to assess which countries around the SCS could be more at risk from the occurrence of such phenomena. Our results show that the worst-case scenarios are produced by eruption/tsunamis from the northern SCS, producing offshore waves up to 10 cm offshore Macau and Hong Kong, and up to 20 cm offshore Manila. In contrast, countries bordering the shallow Sunda Shelf (Malaysia, Thailand, Cambodia, and southern Vietnam) seem less at risk from volcanic meteo-tsunamis, though we observed some amplification effects along the deeper Singapore Strait. This study is the first of its kind in the region and sets the basis to investigate amplification effects, and shallow coastal dynamics at key locations, after integrating higher resolution bathymetry data.