ESR dating of the subsidiary faults in the Yangsan fault system, Korea

The Yangsan fault system is located near heavy industrial complexes and nuclear power plants in the Korean peninsula. We carried out ESR dating of fault rocks from the Wonwonsa and Ihwa faults, two subsidiary faults of the Yangsan fault system. ESR ages are divided into three groups in order of decreasing confidence: multiple plateau ESR ages; single plateau ESR ages; and maximum ESR ages. The Wonwonsa fault was reactivated at least 4 times and the Ihwa fault at least 2 times within the Quaternary period. Long-term cyclic fault activity of some subsidiary faults of the Yangsan fault system occurred in the Pleistocene, and suggests the possibility of continued activity on this fault system.