Shallow segment rupture associated with the 2025 Kamchatka earthquake inferred from ALOS-2/PALSAR-2 InSAR

We detected coseismic deformation associated with the 2025 Kamchatka earthquake using Advanced Land Observing Satellite-2 (ALOS-2) ScanSAR (wide-swath) data. The coseismic deformation revealed a predominantly eastward displacement of more than 1.5 m, with smaller vertical movement observed on the southern Kamchatka Peninsula. Our best-fit model prefers a shallow, near-trench slip concentration on the order of 10–15 m at 10–20 km depth and a similar along-strike extent to that of the 1952 M9.0 earthquake inferred from tsunami or historical records in previous studies. Furthermore, the trenchward rupture in 2025 overlapped the seismicity gap observed between 1970 and 2019 as well as areas of strong plate coupling, suggesting a decades-long accumulation of slip deficit. In contrast, the upper-bound of slip deficit budget is insufficient to explain the inferred peak coseismic slip, because the slip deficit reaches at most ~ 6 m, even with full coupling and a convergence rate of about 80 mm/yr since the 1952 event. The imbalance between the slip deficit budget and the coseismic slip may reflect a partial failure to release slip deficit due to the 1952 earthquake or fine-scale slip segmentation in the subduction zone; however, the model resolution is limited to resolve these interpretations uniquely.