An inferred active fault has been reported at the foot of Mt. Wakurayama in the eastern part of Matsue City, Shimane Prefecture, southwest Japan. No fault outcrop has been identified along the surface trace of the inferred fault. The basement rock at Mt. Wakurayama is mainly the Wakurayama Dacite, which yields whole-rock K-Ar ages of 6.3-5.0 to 0.9-0.7 Ma.

　 We conducted a field survey to search for fault outcrops and determine the age of basement rocks along the trace. An exposed fault was found. The fault strikes ENE, dips steeply to the north, and is accompanied by a damage zone that contains shear joints and fault breccia. Structures in the fault breccia and striations on the fault plane indicate a dextral sense of shear. The geometry and sense of displacement of the fault are consistent with those of the inferred active fault; therefore, we infer that the lineament resulted from displacement on the fault. The fault cuts dacite that yields a U-Pb zircon age of 0.83±0.03 Ma, which indicates that the fault was active in and/or after the middle Pleistocene. The net-slip rate of the fault, as estimated from the fault outcrop, is roughly 0.25 mm/yr.

　 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.