Absolute dating of active faults and the assessment of fault activity using ESR dating method: The case of the Itoigawa–Shizuoka Tectonic Line Active Fault System

I carry out the assessment of fault activity of the Shimotsuburai and Hoozan faults belonging to the Itoigawa-Shizuoka Tectonic Line Active Fault System located at the northeast and east edges of the South Alps of Japan, using ESR (electron spin resonance) dating method. The age of the latest fault movement (T a ) of the Shimotsuburai fault, which is recognized as an active fault, is estimated as T a ≤ 1.04±0.14 Ma. This result means that the principle of ESR dating method of fault movement is sustained. On the other hand, the age of the latest fault movement of the Hoozan fault, which is regarded as an estimated active fault by a topographical feature, is estimated as T a ≤ 0.58±0.10 Ma. Therefore, I conclude that the Hoozan fault is probably an active fault having moved since the Middle Pleistocene.