HR: 1340h
AN: S13B-1060    [Abstracts]
TI: Two-dimensional crustal velocity structure of the southern Korea from the first crustal refraction experiment in Korea
AU: Baag, C
EM: baagce@snu.ac.kr
AF: School of Earth and Environmental Sciences, Seoul National University, Seoul, 151-742 Korea, Republic of
AU: * Cho, H
EM: hmcho@seismic.snu.ac.kr
AF: School of Earth and Environmental Sciences, Seoul National University, Seoul, 151-742 Korea, Republic of
AU: Moon, W
EM: wmoon@eos1.snu.ac.kr
AF: School of Earth and Environmental Sciences, Seoul National University, Seoul, 151-742 Korea, Republic of
AU: Lee, J
EM: jung@knu.ac.kr
AF: Department of Geology, Kyungpook National University, Daegu, 702-701 Korea, Republic of
AU: Jung, H
EM: hjjung@kunsan.ac.kr
AF: Department of Ocean System Engineering, Kunsan National University, Kunsan, 573-701 Korea, Republic of
AU: Kim, K
EM: kykim@cc.kangwon.ac.kr
AF: Department of Geophysics, Kangwon National University, Chunchon, 200-701 Korea, Republic of
AB: We present the data and a seismic velocity profile of the crust along a seismic transect in Korea. The first crustal refraction experiment in Korea was carried out along the 300 km long survey profile through the central part of the southern Korea in the NW-SE direction in December 2002. 198 portable seismometers including 28 three-component ones were deployed at approximately 1.5 km interval. The NE-SW survey profile is almost normal to the major structural trend in Korea. Two shots were exploded in 100 m deep drill wells at the western end and the mid-point of the profile using 1000 kg and 500 kg explosives, respectively. Seismic signals were recorded on 195 receivers out of 198 at a rate of 120 samples per second. The traveltimes of P wave phases, Pg, PiP, PmP, and Pn were identified and shear wave phases, Sg and SmS were also observable on a reduced traveltime plot. A forward modeling scheme of Zelt and Smith (1992) was used to produce the layered P velocity model. The traveltimes of P wave phases and Sg and SmS phases were matched simultaneously under the Poisson solid assumption of crustal material. An iterative modeling resulted in a layered crustal velocity model in which the thickness varies from 28 km to 34 km. Upper crustal velocities range from 5.44 to 6.03 km/s and lower crustal velocities from 6.47 to 6.77 km/s. The underlying mantle has a velocity 7.95 km/s. The mid-crustal reflections recognized in the western part were considered to be representative of the Conrad and it was modeled as a weak velocity discontinuity, vanishing to the east. The crust appears thickest around the middle area and thinnest at the eastern end, located in the Cretaceous Gyeongsang Basin characterized by about 5 km deep surface low velocities. The low velocities also appears in the area of the Okchon fold belt in the central part. The depth to the Moho and P velocities presented here are consistent with those by Park et al., (2003) estimated from the traveltimes of PmP phases recorded on the earthquake network in Korea.
DE: 7218 Lithosphere and upper mantle
SC: Seismology [S]
MN: 2004 AGU Fall Meeting