Paleoseismology of the Yangsan Fault, southeastern part of the Korean Peninsula

The NNE-trending Yangsan Fault (YSF) is the most prominent fault in the southeastern part of the Korean Peninsula
and has a continuous trace about 200 km long. Activity on this fault was recently investigated using aerial
photographs, topographic analysis, and trenching. The geomorphologic evidence of Late Quaternary faulting is
clearly recognized on both the northern (Yugyeri and Tosung-ri areas) and southern parts (Eonyang to Tongdosa
area) of the fault. The main YSF is marked by a zone of shattered rock that is tens of meters wide and zone of fault
gouge. During the Late Quaternary, right-lateral movement occurred mainly on the southern part, as shown by lowangle
striations on the fault plane, elongation of deformation features in the fault gouge. The estimated vertical slip
rate is about 0.02-0.07 mm/yr, and the lateral slip rate may be several times larger than the vertical rate. The most
recent event occurred prior to deposition of Holocene alluvium. In the northern part, the fault locally changes trend
to almost N-S, dips to the east and has reverse movement. The average vertical slip rate is estimated less than
0.1 mm/yr. The most recent event probably occurred after 1314 cal. years BP (A.D. 536).