The 2025 Mw 7.6 Aomori Megathrust Earthquake in Northeast Japan: Failure of a Structurally and Rheologically Bounded Asperity Beneath a Cold Mantle Wedge

Abstract To explore mechanisms of rupture segmentation, we invert coseismic GNSS offsets for the 2025 Mw 7.6 Aomori, Japan earthquake. Our preferred curved‐fault solution images a compact thrust rupture at 25–50 km depth with peak slip ∼2.5 m near 35 km. Slip is centered beneath the offshore Hidaka Basin and terminates near a sharp change in slab dip azimuth, indicating controls from forearc structure and local slab bending. The event reactivated the deeper asperity of the 1968 Mw 8.3 Tokachi‐oki earthquake, whereas the 1968 shallow patch that re‐ruptured in 1994 remained unruptured, consistent with depth‐zonation between the mantle‐wedge corner and a downdip limit ∼60 km. Abundant background seismicity and slow earthquakes flank the slip patch, indicating highly heterogeneous megathrust properties, while afterslip and aftershocks are concentrated within and adjacent to the coseismic rupture. Therefore, structural and rheological factors jointly bound fast‐rupture extent and may control fast‐to‐slow slip transitions beneath the continental Moho.