Paleoseismological Study and Evaluation of Maximum Earthquake Magnitude along the Yangsan and Ulsan Fault Zones in the Southeastern Part of Korea

남한 남동부 양산단층대와 울산단층대의 고지진 연구와 최대 지진 규모 평가

  • Kyung, Jai-Bok (Dept. of Earth Science Education, Korea National University of Education)
  • 경재복 (한국교원대학교 지구과학교육과)
  • Received : 2010.08.05
  • Accepted : 2010.08.24
  • Published : 2010.08.31

Abstract

The paleoseismological study in Korea has begun along the Yangsan fault zone (YFZ) and Ulsan fault zone (UFZ) since 1994. Some evidences related to late Quaternary movement are found at only some part of the YFZ, such as Pyonghae, Yuge, and Eonyang-Tongdosa areas. However, it is found along the most of the UFZ except the northen and southern ends of the fault. The dominant time span of faulting events along the YFZ and UFZ are quite different, and 500 ka to 200 ka and 300 ka to recent time, respectively. The dominant faulting senses of the YFZ and UFZ are right-lateral strike slip and reverse, respectively. These senses correspond well with the focal mechanism of recent occurring earthquakes along these two fault zones. If we evaluate the intensity of the activity of the YFZ from the average slip rate, which is 0.1~0.04 m/ka, it is comparable with the faults of higher C class in Japan. The slip rate of UFZ, which is 0.2~0.06 m/ka, is comparable with the faults of lower B to higher C class. Based on the relationship between maximum displacement and magnitude, the maximum earthquake magnitude is evaluated to be 6.8 and 7.0 in the YFZ and UFZ, respectively. An intensive studies are needed to clarify the problems such as segmentation of faults, return period, and geological evidences related to historical earthquakes.

Acknowledgement

Supported by : 한국교원대학교

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