Near-field GNSS evidence for repeated rupture of an Mw7-class interplate source region within the 1968 Mw8.3 Tokachi-oki earthquake rupture area

Recurrent ruptures of persistent asperities on the fault could explain the pattern of consecutive large earthquakes. Near-field geodetic evidence that directly constrains the spatial relationship between the coseismic slip areas of consecutive large earthquakes is limited. We compared the coseismic displacements for four M~7.5 interplate earthquakes in 1994, 2011, 2025, and 2026 using permanent Global Navigation Satellite System (GNSS) data in the northern part of the Japan trench subduction zone, and estimated their fault models. This study provides direct geodetic evidence for recurrent rupture of the source region by showing a nearly identical pattern of horizontal displacement between the 2011 and 2026 earthquakes. The estimated source regions suggest the 2025, 1994, and 2026 earthquakes ruptured the northern, central, and southern parts of the 1968 M w 8.3 Tokachi-oki earthquake, respectively. The recent ruptures in 2025 and 2026 may have implications for future rupture of the central asperity ruptured in 1994, through tectonic and coseismic stress loading.