Crustal Structure of the Southern Korean Peninsula from Seismic Waves Generated by Large Explosions in 2002 and 2004 |
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| Authors: | Ki Young Kim Jung Mo Lee Wooil Moon Chang-Eob Baag Heeok Jung Myung Ho Hong |
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| Institution: | (1) Department of Geophysics, Kangwon National University, 192-1 Hyoja-2-dong, Chunchon, 200-701, Korea;(2) Department of Geology, Kyungpook National University, Sangyeok-2-dong, Daegu, 702-701, Korea;(3) School of Earth and Environmental Sciences, Seoul National University, Shinlim-9-dong, Gwanak-gu, Seoul, 151-747, Korea;(4) Department of Ocean System Engineering, Kunsan National University, Meeryong-dong, Gunsan, 573-701, Korea |
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| Abstract: | In order to investigate the velocity structure of the southern part of the Korean peninsula, seismic refraction profiles were
obtained along a 294-km WNW-ESE line and a 335-km NNW-SSE line in 2002 and 2004, respectively. Seismic waves were generated
by detonating 500–1000 kg explosives in drill holes at depths of 80–150 m. The seismic signals were recorded by portable seismometers
at nominal intervals of 1.5–1.7 km. Separate velocity tomograms were derived from first arrival times using a series expansion
method of travel-time inversion. The raypaths indicate several mid-crust interfaces including those at approximate depths
of 2–3, 15–17, and 22 km. The Moho discontinuity with refraction velocity of 7.8 to 8.4 km/s has a maximum depth of 37–39
km under the southern central portion of the peninsula. The Moho becomes shallower as the Yellow Sea and the East Sea are
approached on the west and east coasts of the peninsula, respectively. The depth of the 7.6 km/s velocity contour varies from
29.4 km to 36.5 km. The discrepancy in depth between the seismological Moho and the interpreted critically refracting interface
may result from the presence of a gradual transition between the crust and mantle. The velocity tomograms show particular
crustal structures including (1) the existence of an over 70-km wide low-velocity zone centered at 6–7 km depth under the
Okchon fold belt and Ryeongnam massif, (2) existence of high-velocity materials under the Gyeongsang basin, and (3) the downward
extension of the Yeongdong fault to depths greater than 10 km. |
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| Keywords: | Velocity structure Korean Peninsula travel-time inversion mid-crust interface Moho discontinuity |
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