HR: 1340h
AN: NG43B-0572    [Abstracts]
TI: AMT and MT Survey at the Mid-mountain Area of Jeju Island, Korea
AU: * Lee, T
EM: megi@kigam.re.kr
AF: Korea Institute of Geoscience and Mineral Resources (KIGAM), 30 Gajeong-dong, Yuseong-gu, Daejeon, 305-350 Korea, Republic of
AU: Song, Y
EM: song@kigam.re.kr
AF: Korea Institute of Geoscience and Mineral Resources (KIGAM), 30 Gajeong-dong, Yuseong-gu, Daejeon, 305-350 Korea, Republic of
AU: Uchida, T
EM: uchida-toshihiro@aist.go.jp
AF: Institute for Geo-Resources and Environment, AIST, 1-1-1 Higashi, No. 7, Tsukuba, 305-8567 Japan
AB: Jeju is a Quaternary volcanic island located at about 90 km south of the Korean peninsula. The basement rock is Cretaceous granites and tuff, which are overlain successively by unconsolidated sedimentary layer (USL), Basal basalt, Seogwipo Formation and basalt. USL is distributed all over the island in the depth range of +30 to -245 m above sea level and is known to be electrically conductive (< 10 ohm-m) in otherwise resistive layers. In the year 2004, AMT (Audio-Frequency Magnetotelluric) and MT (Magnetotelluric) survey has been carried out along the two survey lines of north-south direction and roughly 25 km apart each other. The purpose of the survey is to image the deep structures and to figure out any possible remnant volcanic evidences beneath the island for geothermal applications. Comparison of the two-dimensional (2-D) inversion results using MT band data only and those using both AMT and MT bands say that it is helpful for us to include AMT band as well as MT band in the inversion to interpret the deep structure with better resolution by way of including shallow part with finer meshes. 2-D models from the 2-D inversions of the two profiles show a thick layer having around 10 ohm-m in the depth of a few hundred meters throughout the survey area, which corresponds to the USL. And they also show conductive anomalies at the central part of each survey lines. Most reasonable interpretation for the anomalies would be a lineament, which is known to extend along the major axis of the island from the analysis of the Landsat TM images and crosses the middle parts of the survey lines. Based on the 2-D models, a three-dimensional modeling including the topography of the island has been performed, which showed a good agreement with the measured apparent resistivity and phase curves.
DE: 0925 Magnetic and electrical methods (5109)
DE: 5109 Magnetic and electrical properties (0925)
SC: Nonlinear Geophysics [NG]
MN: Fall Meeting 2005