In order to analyze the distribution characteristics of surface displacements caused by the 2016 Kumamoto Earthquake (Mw 7.0), we conducted the surface deformation analysis called three dimensional Geomorphic Image Velocimetry in the easternmost part of the Futagawa-Hinagu fault zone, using airborne laser scanning data before and after the earthquake. As a result, we confirmed the presence of a surface displacement vector discontinuity extending approximately 2.7 km eastward from the Nigorikawa River fault zone (surface rupture zone along the Nigorikawa River, located to the east of the Futagawa-Hinagu fault zone). In fact, by field surveys, we confirmed a scarp, approximately 30 m long with cracks of about 5 m in length, and a relative height of about 0.3 m, at a site in the Nagano area of Minamiaso Village that is on the surface displacement vector discontinuity. Comparing topographic cross sections from 1 m digital elevation model before the earthquake with those from ground data point cloud obtained through airborne laser scanning after the earthquake, the data after the earthquake showed the uphill-facing scarp. In contrast, similar topographical features were not observed in the data before the earthquake, suggesting a high possibility that this scarp was formed during the earthquake. The surface displacement vector discontinuity, characterized by left-lateral strike-slip and southern uplift, along with the scarp and the cracks found in the Nagano area, suggests that it is the eastern extension of the Nigorikawa River fault zone. However, determining whether it corresponds to a primary surface rupture, a secondary surface rupture, or an induced surface rupture, defined by Suzuki (2017), is difficult.
