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Near-surface geophysical studies in the Ulsan Fault Zone of Korea  

Kim, Ki-Young (Department of Geophysics, Kangwon National University)
Kim, Dong-Hoon (SEKOGEO Co. Ltd.)
Lee, So-Young (Department of Geophysics, Kangwon National University)
Publication Information
Geophysics and Geophysical Exploration / v.11, no.1, 2008 , pp. 78-84 More about this Journal
Abstract
Recent earthquakes near nuclear power plants in Korea have triggered public concerns about possible seismicity of the Ulsan Fault Zone in the south-eastern part of the Korean peninsula. To reveal subsurface structures of this fault zone, we conducted high-resolution seismic refraction and reflection surveys, and closely spaced gravity measurements in the Dongchon River valley north of Ulsan, Korea. Here alluvium covers the north-south trending fault zone in a 1-km wide valley. Both source points and receivers were spaced at 5-m intervals for the 24-channel seismic refraction and reflection methods, along two profiles of 835 m and 415 m length. Gravity data were also measured along these profiles at 131 stations using a 10-m interval. Synergetic interpretation of seismic refraction, high-resolution seismic reflection, and gravity surveys across the valley indicates that the Ulsan Fault Zone was formed by apparent north-south strike-slip motions during the Cretaceous, and that some faults may have been reactivated by east-west compressional or transpressional stresses during the Tertiary or Quaternary.
Keywords
Ulsan Fault; high-resolution seismic survey; refraction; reflection; gravity; reactivated;
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