3. EM/GPR Imaging Technologies
Topography and Sea Effects on MT Responses Observed in Jeju Island, Korea
Yoonho Song, Myung Jin Nam and Tae Jong Lee
Korea Institute of Geoscience and Mineral Resources (KIGAM), Korea.
Abstract
A magnetotelluric (MT) survey has been performed along four lines in Jeju Island located at South Sea of Korea. Jeju Island is a volcanic island of Quaternary eruption. The purpose of the MT survey was to see if there still remain thermal resources and to see if there exist deeply extended fractures or aquifer system beneath mid-mountain region. The island is of oval shape; 31 km wide and 73 km long, and has famous Halla Mountain of 1,950 m high in its center. Because the island is surrounded by electrically conductive sea and has big change in topography, measured MT data in terms of impedance is seriously biased by distortion of electric fields. We analyze the topography and sea effects on the measured MT data through three-dimensional modeling data which can accommodate topographic variation with edge-element finite element approximation to electric field formulation of electromagnetic responses to subsurface. We also show the validity of our analyses through comparing the theoretical data with observed data at some locations.
Last modified: Fri May 12 08:43:46 2006