11:15 AM - 11:30 AM
[SSS11-08] Fault outcrops and geological fault offset around a lineament reported in Hamada City, Shimane Prefecture
Keywords:active fault, lineament, fault outcrop, San-in shear zone
The Sanin region is known as one of the high-shear strain zones in Japan. However, the number of active faults identified in this region is smaller than in other regions, and a detailed investigation is required. An ENE-WSW trending inferred active fault, whose length is about 5 km is reported by fault topography interpretation (Imaizumi et al. eds., 2018) around Usirono Town, Hamada City, Shimane Prefecture. In addition, a reverse fault outcrop is reported about 500m north of the inferred active fault.
This research aims to clarify the correlation between the inferred active fault and the fault activity and the reverse fault formation process by geological survey. Based on the geological map and the structure recorded in the fault rock, the fault was determined to be a right-lateral strike-slip fault. In addition, a reverse fault was determined to extend in a north-northeast to south-southwest direction from the center to the western part of the study area on the geologic map and geologic cross-section, and another reverse fault was inferred to be west of this fault. It seems that they were formed under the E-W compressional stress field. Moreover, the inferred active fault might be activated after two reverse faults had been activated. The inferred active fault and the reverse faults will act in the future under the present stress field because the reverse fault cut the Pleistocene sediments. The detailed activity of the active faults was not clarified in this study and is a subject for future work.
This research aims to clarify the correlation between the inferred active fault and the fault activity and the reverse fault formation process by geological survey. Based on the geological map and the structure recorded in the fault rock, the fault was determined to be a right-lateral strike-slip fault. In addition, a reverse fault was determined to extend in a north-northeast to south-southwest direction from the center to the western part of the study area on the geologic map and geologic cross-section, and another reverse fault was inferred to be west of this fault. It seems that they were formed under the E-W compressional stress field. Moreover, the inferred active fault might be activated after two reverse faults had been activated. The inferred active fault and the reverse faults will act in the future under the present stress field because the reverse fault cut the Pleistocene sediments. The detailed activity of the active faults was not clarified in this study and is a subject for future work.