The Atotsugawa Fault is an active right-lateral strike-slip fault about 70 kilometres long in the mountainous Hida region of central Honshu, near the Japanese Alps in Gifu Prefecture. It is one of the best-studied inland faults in Japan and a natural laboratory for understanding continental fault behaviour.
The fault trends roughly east-northeast and shows evidence of both locked and creeping segments, with part of the fault slipping slowly and aseismically while other parts remain locked and capable of storing strain. Dense geodetic and seismic networks monitor its behaviour in great detail.
The Atotsugawa Fault produced the destructive 1858 Hietsu earthquake, estimated near magnitude 7, which caused landslides and heavy damage in the mountainous region. Its combination of documented historical rupture and detailed modern monitoring makes it a key reference for assessing the hazard of inland Japanese faults.