Seismic Hazards in Vanuatu: The December 2024 M7.3 Earthquake and Regional Tectonic Context

Vanuatu lies along the tectonically active New Hebrides island arc in the southwestern Pacific, where convergence between the Australian and Pacific plates generates frequent large earthquakes. The subduction zone features the Australian plate descending beneath the Pacific plate at rates exceeding 10 cm per year, producing intermediate-depth seismicity and occasional megathrust events. Port-Vila, the capital on Efate Island, sits near this plate boundary, exposing the region to recurrent strong shaking.

On 17 December 2024 at 01:47 UTC, a magnitude 7.3 earthquake struck 24 km west-northwest of Port-Vila at a depth of 54.3 km. The event occurred within the subducting slab, consistent with the slab's geometry beneath the arc. No immediate tsunami warning was issued, reflecting the earthquake's depth and mechanism.

This earthquake continues a pattern of significant seismic activity near Efate. Since 2000, multiple magnitude 7+ events have occurred within 75 km of the 2024 epicenter. A magnitude 7.3 event struck on 10 August 2010 approximately 16 km from the recent rupture area, followed hours later by another magnitude 7.3 shock. On 20 August 2011, a magnitude 7.1 earthquake occurred 64 km south of Port-Vila, and a magnitude 7.2 event took place 71 km south-southwest on the same day. Earlier, a magnitude 7.2 quake was recorded on 2 January 2002, 50 km west-northwest of the capital.

These events cluster along the subduction interface and within the downgoing slab, highlighting persistent strain accumulation and release. Intermediate-depth earthquakes like the 2024 event often result from internal deformation of the slab rather than the main plate-boundary thrust. Historical records show Vanuatu experiences some of the highest rates of large earthquakes globally, with frequent aftershock sequences and occasional damaging ground motions in populated areas.

Ongoing monitoring by regional seismic networks supports hazard assessment and preparedness efforts. The combination of shallow crustal faults, the subduction megathrust, and intraslab seismicity creates a complex risk profile for Vanuatu's islands. Continued study of these patterns aids in refining probabilistic seismic hazard models for the arc.

References USGS Earthquake Catalog (events since 2000) Global CMT catalog for focal mechanisms Pacific Tsunami Warning Center archives