Deep-Seated Seismicity in the Fiji Region: The November 2022 Magnitude 7.0 Event

The Fiji region lies within a tectonically complex portion of the southwestern Pacific, where convergence between the Pacific and Australian plates produces frequent deep-focus earthquakes. The 12 November 2022 magnitude 7.0 event occurred at 07:09 UTC at a depth of 579 km, highlighting the area’s capacity for significant seismicity well below the Earth’s surface. Fiji sits atop the Fiji Plate, bounded by the North Fiji Basin to the north and the Lau Basin to the east. Subduction along the Tonga and Vanuatu trenches drives the descent of cold oceanic lithosphere into the mantle, generating earthquakes at depths exceeding 500 km. These events typically produce limited surface shaking yet remain important for understanding slab dynamics and mantle rheology. Historical records show recurrent strong earthquakes in the same vicinity. Since 2000, three events of magnitude 7.0 or greater have struck within a 77 km radius of the 2022 epicenter:

• The magnitude 7.0 earthquake of 12 November 2022.
• The magnitude 7.1 earthquake of 1 November 2014, located 77 km away.
• The magnitude 7.2 earthquake of 2 January 2006, located 27 km away. These deep events reflect the steeply dipping slab geometry beneath the region. Focal mechanisms commonly indicate downdip tension or compression consistent with the phase transitions and dehydration reactions occurring within the subducting plate at depths greater than 400 km. Seismic monitoring networks operated by the United States Geological Survey and regional agencies continue to track activity, providing data that refine models of Pacific plate subduction. The 2022 earthquake produced no reported damage or tsunami, consistent with its great focal depth and the attenuating effects of the overlying mantle and crust. Ongoing research into the thermal structure and mineralogy of the subducted slab beneath Fiji contributes to broader understanding of intermediate-depth and deep earthquake mechanisms worldwide.

References

United States Geological Survey Earthquake Catalog (earthquake.usgs.gov) International Seismological Centre On-line Bulletin (isc.ac.uk)