Quaternary reactivation of Tertiary faults in the southeastern Korean Peninsula: Age constraint by optically stimulated luminescence dating

Abstract

Two groups of Quaternary faults occur in the southeastern Korean Peninsula. The first group is north‐northeast‐striking, high‐angle dextral strike–slip faults. The second group is north‐northeast‐striking, low‐angle reverse faults that represent the reactivation of the pre‐existing normal faults. Optically stimulated luminescence dating of Quaternary sediments cut by one of the reverse faults constrains the faulting age to post‐32 Ka. These faults seem to be capable of further slip under the current tectonic stress regime, as determined by recent earthquake events in northeast Asia. Therefore, the traditional concept that the southeastern Korean Peninsula is seismically stable should be reappraised.

Cenozoic deformation history of the area around Yangnam-Yangbuk, SE Korea and its tectonic significance

“…Nicholson et al, 1986;Kim et al, 2001) or tear faults between NE-SW or N-S trending thrust faults. This interpretation agrees with that reported for Quaternary thrust faults in this region (KIGAM, 1998;Ree et al, 2003;Kim et al, 2004b). Most of the Quaternary faults may have been reactivated under changed stress condition along pre-existing normal faults (Ree et al, 2003;Kim et al, 2004b) developed at the time of right-lateral movement of the Yangsan Fault.…”

“…This interpretation agrees with that reported for Quaternary thrust faults in this region (KIGAM, 1998;Ree et al, 2003;Kim et al, 2004b). Most of the Quaternary faults may have been reactivated under changed stress condition along pre-existing normal faults (Ree et al, 2003;Kim et al, 2004b) developed at the time of right-lateral movement of the Yangsan Fault. This interpretation is also supported by the thrust geometry of the reactivated faults.…”

“…1 and 15;Yoon and Chough, 1995). In the Pohang-Ulsan area to the east of the Yangsan Fault, several Quaternary faults have been reported recently (KIGAM, 1998;Ree et al, 2003;Kim et al, 2004b). This area can be interpreted as an overstepping or relay zone between the Yangsan Fault and the Hupo Fault (e.g.…”

“…This interpretation is also supported by the thrust geometry of the reactivated faults. The curved fault tips near the surface at Suryeom (KIGAM, 1998;Ree et al, 2003) and Eupchon (KIGAM, 1998;Kim et al, 2004b) faults may indicate reactivation of pre-existing normal faults with steeper angles. In summary, strike-slip faults were reactivated as strike-slip or oblique slip faults (e.g.…”

“…1). Electron spin resonance (ESR) dating of the fault zone and optically stimulated luminescence (OSL) dating of the Quaternary marine terrace sediments has been carried out because of concern about neotectonic fault activity (KIGAM, 1998;Cheong, 2002;Inoue et al, 2002;Ree et al, 2003;Choi et al, 2003). This area is tectonically linked to the spreading of the East Sea (Japan Sea) (Fig.…”