Geosciences Journal

, 10:159 | Cite as

The offshore Uljin, Korea, earthquake sequence of April 2006: seismogenesis in the western margin of the Ulleung Basin

  • Tae-Seob KangEmail author
  • Jin Soo Shin


An unusual earthquake sequence comprising 11 events with magnitude range ofM L 2.0 to 3.2 occurred off the eastern coast of the southern Korean Peninsula in April 2006. Since there is no obvious mainshock in this sequence unlike a typical mainshock-aftershock sequence, the seismicity pattern shows the characteristics of swarm behavior. Focal mechanism of the largest event (M L 3.2) on the 29 of April is normal to strike-slip faulting. Hypocenter relocations of nine events improve the epicenter locations that fall within an area with a radius of about 0.7 km while depths are less well constrained with ranges of 1.6 km to 13.0 km. We propose that a swarm behavior of the sequence is closely related to the marginal geometry of the Ulleung Basin and the regional stress regime. The fact that epicenters of the April 2006 sequence are at the same transitional zone of continental to rifted continental crust as that of the 29 May 2004,M w 5.1, earthquake indicates that the Ulleung Fault is seismically active.

Key words

earthquake sequence swarm behavior Ulleung Basin Ulleung Fault 


  1. Chang, S.-J. and Baag, C.-E., 2005, Crustal structure in southern Korea from joint analysis of telescismic receiver functions and surface-wave dispersion. Bulletin of the Seismological Society of America, 95, 1516–1534, doi:10.1785/0120040080.CrossRefGoogle Scholar
  2. Chang, S.-J. and Baag, C.-E., 2006, Crustal structure in southern Korea from joint analysis of regional broadband waveforms and travel times. Bulletin of the Seismological Society of America, 96, 856–870, doi:10.1785/0120040165.CrossRefGoogle Scholar
  3. Cho, H.-M., Kim, H.-J., Jou, H.-T., Hong, J.-K. and Baag, C.-E., 2004, Transition from rifted continental to occanic crust at the southeastern Korean margin in the East Sea (Japan Sea). Geophysical Research Letters, 31, L07606, doi:10.1029/2003GL019107.CrossRefGoogle Scholar
  4. Chough, S.K., Lee, H.J. and Yoon, S.H., 2000, Marine Geology of Korean Seas. 2nd ed., Elsevier, Amsterdam, p. 313.Google Scholar
  5. Kang, T.-S. and Baag, C.-E., 2004, The 29 May 2004,M w=5.1, offshore Uljin carthquake, Korea. Geosciences Journal, 8, 115–123.CrossRefGoogle Scholar
  6. Lay, T. and Wallace, T.C., 1995, Modern Global Scismology. Academic Press, San Diego, p. 521.Google Scholar
  7. Park, S.-C. and Mori, J., 2005, Source parameters of the May 29, 2004 South Korea carthquake (M L 5.2). Earth, Planets and Space, 57, 471–475.Google Scholar
  8. Snoke, J.A., Munsey, J.W., Teague, A.G. and Bollinger, G.A., 1984, A program for focal mechanism determination by combined use of polarity and SV-P amplitude data. Earthquake Notes (Abstract), 55, 15.Google Scholar
  9. Waldhauser, F. and Ellsworth, W.L., 2000, A double-difference carthquake location algorithm: method and application to the northern Hayward fault, California. Bulletin of the Seismological Society of America, 90, 1353–1368.CrossRefGoogle Scholar

Copyright information

© Springer 2006

Authors and Affiliations

  1. 1.Earthquake Research Center, Geological and Environmental Hazards DivisionKorea Institute of Geoscience and Mineral ResourcesDaejeonKorea

Personalised recommendations