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전기 전자 탐사법에 의한 지하 영상화 기술 연구 [1998]

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자료유형 KIGAM 보고서
서명 전기 전자 탐사법에 의한 지하 영상화 기술 연구 [1998]
저자 이명종
언어 KOR
청구기호 KR-98-C-09-1998-R
발행사항 韓國資源硏究所, 1998
초록 지형을 고려한 전기비저항 탐사자료의 3차원 역산: The interpretation of resistivity survey data has mainly been done under the assumption of two-dimensional geological structure. Since the real earth is, however, fully three-dimensional (3-D) and very complicated in nature, such an assumption of two-dimensional earth may often lead to misinterpretation. In this study, we developed a 3-D inversion method based on the finite element calculation of model responses, which can effectively accomodate the irregular topography. In solving the inverse problem, the iterative least-squares approach comprising the smoothness-constraints was taken along with the reciprocity approach in the calculation of Jacobian. Futhermore the Active Constraint Balancing, which has been recently developed by ourselves to enhance the resolving power of the inverse problem, was also employed. Since our new algorithm accounts for the topography in the inversion step, topography correction is not necessary as a preliminary processing and we can expect a more accurate image of the earth. The newly developed inversion algorithm was first applied to the synthetic data sets for simple earth models with irregular topography. These results were compared to the inversion results when topography is not included in the inversion. When topography data is used in the resistivity inversion, we could get the correct image of the earth, while the results which did not account for the topography produced a distorted image Finally, we applied the 3-D inversion to the real field data sets gathered at highway construction sites and could get reasonable three-dimensional image of the geological structures

시추공내 송신원에 의한 전자탐사반응: Among the geophysical tomography technologies, which are used as high-resolution imaging tools between boreholes, electromagnetic (EM) tomography is a recently introduced one since the accurate measurement of both the amplitude and phase through the borehole equipments has been a difficult technology. Nevertheless, the EM tomography may be a promising tool in such environments as a highly conductive medium in which the radar can not work or as the fiber glass cased hole in which the resistivity tomography can not be applied due to limitation of glavanic contact through casing. The effects of borehole fluid and casing on the borehole EM responses should thoroughly be analyzed since they may affect the resultant image of the earth. In this study, we developed an accurate algorithm for calculating the EM responses containing the effects of borehole fluid and casing when a current-carrying ring is located on the borehole axis. An analytic expression for primary vertical magnetic field along the borehole axis was first formulated and the fast Fourier transform is to be applied to get the EM fields at any location in whole space. The analysis was focused on the effect of borehole fluid since the fiber glass casing, which we frequently meet at field site, has neither conductivity thus nor effect of borehole on the EM responses. Throughout the frequency range, 10 Hz to 100 kHz, tested, there can hardly be seen any noticeable effects of borehole on the EM reponses except in the close vicinity of the current ring, which renders the EM tomography preferable to resistivity technique in application to wide variety of field situation

고주파수 전자기파 임피던스 탐사기술: This article presents a high-frequency electromagnetic (EM) inpedance method that extends the utility of conventional CSMT method to a frequency range from 100 kHz to 100 MHz. In this frequency range diffusion and wave propagation must be considered together. In principle, both the electrical conductivity as well as the permittivity of the earth can be imaged using impedance data gathered on the surface of the earth. The impedance approach has a distinct advantage in that coupling with the source is unnecessary, and that the source can always be positioned far enough away to yield plane waves at the receiver positions. At high frequencies the EM impedance becomes a function of the angle of incidence or the horizontal wavenumber, so the electrical properties cannot be readily extracted without first eliminating the effect of horizontal wavenumber on the impedance. For this purpose, this paper considers two independent methods for accurately determining the horizontal wavenumber, which in turn is used to correct the impedance data. The 'apparent' electrical properties derived from the corrected impedance data show poor visual connections to the real structure, especially for the model with a resistive overburden. The impedance data along with the incidence angles thus estimated however, can be successfully inverted to yield an accurate subsurface layering through the simulated annealing inversion scheme
페이지 108 p.
키워드 전기탐사, 전자탐사, 지하영상화, 지하영상화기술, 토모그래피, 시추공, 전기비저항, 분해능, 3차원역산, 역산, 전기, 전자, 탐사, 송신원, 고주파수, 전자기파, 임피던스
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이명종. (1998). 전기 전자 탐사법에 의한 지하 영상화 기술 연구 [1998]. 韓國資源硏究所.