The 2010 Bonin Islands Earthquake and Regional Tectonics

The Bonin Islands, also known as the Ogasawara Islands, lie in the western Pacific Ocean approximately 1,000 kilometers south of Tokyo. On December 21, 2010, at 17:19 UTC, a magnitude 7.4 earthquake struck the region at a depth of 14.0 kilometers. The event originated directly beneath the islands and represented the strongest earthquake recorded in the area since January 1, 2000. The Bonin Islands form part of the Izu-Bonin-Mariana volcanic arc, created by the subduction of the Pacific Plate beneath the Philippine Sea Plate. This convergent boundary produces frequent seismic activity as the oceanic lithosphere descends into the mantle. The shallow depth of the 2010 event placed it within the upper portion of the overriding plate or near the plate interface, where brittle failure can generate significant ground shaking. Geologically, the islands consist of volcanic rocks and associated sedimentary deposits that record arc volcanism spanning the Eocene to the present. Uplifted limestone terraces and exposed volcanic sequences illustrate long-term tectonic emergence and erosion. The subduction zone has generated numerous historical earthquakes, though the 2010 event stands out for its magnitude and proximity to the island chain within the period examined. No major aftershock sequence or significant tsunami was reported following the mainshock, consistent with its moderate depth and focal mechanism typical of intraslab or interface events in this setting. The tectonic framework continues to drive deformation, with the potential for future large earthquakes along the same plate boundary.

References

USGS Earthquake Catalog (event details for 21 December 2010) Geological Survey of Japan, AIST (Izu-Bonin arc tectonics and volcanic history)