Detection of the eruption of the East Epi submarine volcano, Vanuatu, and its subsequent tsunami on 31 January 2023

Abstract Between the 25th and the 31st of January 2023 an eruption occurred several kilometres East of Epi Island, Vanuatu, an area known to host a submarine volcanic zone including several cones. The largest cone (Epi B) entered regularly in activity in the last century, and images of daily monitoring satellites confirmed its responsibility for the January 2023 eruption. The eruption evolved to Surtseyan on the 31st, producing ash and gas columns reaching more than 100 m above sea level and small pyroclastic surge moving across the water, with subsequent pumice rafts and water discolouration. The eruptive activity is visible on satellite imagery and was well recorded on seismic, hydroacoustic and infrasound stations that are part of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) International Monitoring System (IMS). Although this had no apparent consequences on the nearby communities, a small tsunami was however reported by locals and recorded on the coastal tide gauges of Port Vila ~ 125 km to the south and Luganville ~ 175 km to the north showing maximum amplitude of ~ 5 cm. This data is used to validate the location and timing of the eruption and tentatively propose a tsunami mechanism. As a large part of the Vanuatu population is living in coastal areas, understanding tsunami mechanisms and assessing tsunami hazards associated with submarine eruptions is of main concern. Ultimately, this study aims to bring scientists and risk managers’ attention to a potentially hazardous volcano, through satellite and seismo-acoustic data analysis, numerical simulations of tsunami, and GIS mapping.