South of the 2016 rupture termination: Geodetic constraints on coseismic slip of the 2026 M7.1 Kumamoto Earthquake

The July 28, 2026, M7.1 Kumamoto earthquake occurred on the Hinagu Fault zone in southwest Japan, near the southern termination of the 2016 Kumamoto earthquake sequence. We investigated coseismic deformation from Global Navigation Satellite System (GNSS) and synthetic aperture radar (SAR) data and inferred a two-segment fault source model to examine the spatial relationship among coseismic slip, structural heterogeneity, and the 2016 rupture extent. The 2026 main slip was located south of the southern termination of the 2016 rupture, with a peak of right-lateral slip at shallow depth near the hypocenter, while a normal-slip component was concentrated at greater depth near a fault bend. Slip decreases toward the southwest, where weak slip remains at shallow depth on the southwestern segment; cross-validation tests and a strong-motion waveform inversion supported its robustness. Changes in slip characteristics occur near the fault bend and independently identified contrasts in seismic velocity and geological structure.