Distribution and migration of aftershocks of the 2010 Mw 7.4 Ogasawara Islands intraplate normal-faulting earthquake related to a fracture zone in the Pacific plate

A significant intraplate normal-faulting earthquake (Mw 7.4) occurred 150 km east of the Ogasawara Islands, Japan, on December 21, 2010, revealing that preexisting crustal structures in the Pacific plate influence such seismic events. Aftershocks, mapped using ocean bottom seismographs and multichannel seismic reflection surveys, formed three subparallel lineations along a fracture zone, extending 140 km northwest-southeast—oblique to the trench axis. The study found that aftershock activity migrated over time, initially concentrated in an 80 km central segment near large seamounts and plateaus like the Ogasawara Plateau and Uyeda Ridge, before expanding outward. This migration suggests that crustal heterogeneities, such as fracture zones and seamounts, played a critical role in the main shock rupture. Such findings imply that similar structures may influence intraplate earthquakes in other subduction-related regions.

Obana, K., Takahashi, T., No, T., Kaiho, Y., Kodaira, S., Yamashita, M., Sato, T., & Nakamura, T. (2014). Distribution and migration of aftershocks of the 2010 Mw 7.4 Ogasawara Islands intraplate normal-faulting earthquake related to a fracture zone in the Pacific plate. Geochemistry, Geophysics, Geosystems, 15(4), 1363–1373. https://doi.org/10.1002/2014gc005246