ScholarWorks@경상국립대학교

초록

In strike-slip faults, slip-sense inversion between sinistral and dextral can occur under changing stress fields. Sinistral slip of the Yangsan fault has been reported based on various geological evidence, but direct observation of this in fault rocks is rare. This paper reports the occurrence of sinistral slip on the Yangsan fault, confirmed by observing two fault rock samples collected from the Yangsan fault outcrop, Bogyeonsa area, Pohang, South Korea. In one sample, the sinistral slip was confirmed by shearband boudin. In another sample, it was confirmed by an asymmetric structure defined by the dominant foliation in the P-shear direction and its reflection in the R-shear direction. Unlike the clear indications of dextral slip sense throughout the fault rocks in the study area, the indicators of sinistral slip sense were observed in the limited areas and appeared less well-developed. This suggests that the sinistral slip occurred before the dextral slip, but the absolute timing of the sinistral slip is uncertain, necessitating further research. © 2023 The Geological Society of Korea. All rights reserved.

키워드