Detailed study of the seismic activity preceding and following the 2024 M7.3 Vanuatu earthquake

The earthquake that happened the 17^th of December 2024, located 30km West of Port Vila, the Vanuatu capital, is characterized by an unusual focal mechanism: a nearly-vertical fault with slip predominantly along-dip, and with strike perpendicular to the Vanuatu subduction. In addition to numerous aftershocks, the local seismic networks of Vanuatu and New Caledonia recorded seismic events preceding the mainshock. In this study, we relocate the main event using the local networks. This allows us to better constrain its depth with respect to the available global catalogs, and to determine if it happened in the slab or in the upper plate. A relative relocation of the whole seismic sequence (preshocks and aftershocks) will also allow us to better image the geometry of the fault that activated during this event. A detailed analysis of the preshock activity will give us hints on the mechanisms that led to this large unconventional earthquake.