ESR dating of the Eupchon fault, South Korea

We investigated temporal pattern of Quaternary fault activity of the Eupchon fault zone in the southeastern part of the Korean peninsula, using ESR dating of fault rocks. The counterfeit E′ signal significantly affected the equivalent dose on some samples. In particular, the counterfeit E′ signal tends to affect samples with E′ intensity close to saturation level. Storage at room temperature for 360 days and heating at 170 °C for 15 min. after γ-ray irradiation did not change significantly the intensities, the dose responses and ESR ages for OHC, Al, and Ti signals. ESR ages from the Eupchon fault zone range from 2000 to 500 ka. The fault rocks were reactivated at least five times 2000, 1300, 900–1100, 700–800, and 500–600 ka ago. These data indicate that long-term cyclic fault activity of this fault zone continued into the Quaternary. The results from this study suggest that the Eupchon fault zone can be classified as a potentially active fault and presents some potential seismic hazards to the nuclear power plant in its vicinity.