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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Geophysics and Geophysical Exploration
Journal Basic Information
Journal DOI :
Korean Society of Earth and Exploration Geophysicists
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Volume & Issues
Volume 3, Issue 4 - Nov 2000
Volume 3, Issue 3 - Aug 2000
Volume 3, Issue 2 - May 2000
Volume 3, Issue 1 - Feb 2000
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Detection of Sea-water Intrusion Caused by Tidal Action Using DC Resistivity Monitoring
Hwang, Hak-Soo ; Lee, Sang-Kyu ; Ko, Dong-Chan ; Kim, Yang-Soo ; Park, In-Hwa ;
Geophysics and Geophysical Exploration, volume 3, issue 1, 2000, Pages 1~6
area studied is located in Sukchun-ri, Hwasung-koon, the southern part of Kyeonggi-do. Even though this site has been known as a contaminated area caused by seawater intrusions, geophysical and geochemical surveys have never been carried out at the site to determine the extent of the seawater contamination and to investigate whether the seawater intrusion is in progress. The purpose of this study is to determine the extent of seawater contamination and a preferred channel of the seawater intrusion using geophysical methods such as DC resistivity surveys with Schlumberger array and a dipole-dipole array. In order to determine whether the seawater intrusion is in progress in the area, DC resistivity monitoring with Schlumberger array was performed. According to the resistivity map obtained from the inversion of the resistivity data measured with Schlumberger array, the study area is divided into two districts as relatively lowly resistive (less than 30 ohm-m) and highly resistive (more than 30 ohm-m) areas. The distribution of the lowly resistive area is consistent with the distribution of the layer composed of clay minerals, and the resistivity of this layer decreases slowly as approaching to the old seashore. Hydrogeological analysis shows that the clay layer within a distance of about 200 m from the seashore has been already contaminated by sea-water and its electric conductivity is 8 times higher than that of the sand layer covered by the clay layer. According to the results of the 2-dimensional DC resistivity surveys with a dipole-dipole array, there are two preferred channels of the seawater intrusion in the site, and both the channels are in the NW-SE direction from the old seashore. The lowly resistive zone in the southern channel extends to a depth of 80 m. The DC resistivity monitoring with Schlumberger array was carried out along the preferred channel which has the low resistivity Bone (fracture zone) that extended to a depth of 80 m. The time series of apparent resistivity, measured at a distance of 260 m from the old coast line, fluctuates with a period of 12 hours. From these observations, it can be concluded that the seawater intrusion caused by tidal action is still in progress along the fractured zone interpreted by the DC resistivity surveys with a dipole-dipole array.
Impedance Estimation from 3-D Seismic Data
Lee, Doo-Sung ;
Geophysics and Geophysical Exploration, volume 3, issue 1, 2000, Pages 7~12
The paper discusses a data processing methodology that derives a three dimensional porosity volume information from the 3-D seismic dataset. The methodology consists of preprocessing and inversion procedures. The purpose of the preprocessing is balancing the amplitudes of seismic traces by using reflectivity series derived from sonic and density logs. There are eight sonic logs are available in the study area; therefore, we can compute only 8 balance functions. The balance function for every seismic trace was derived from these 8 balance functions by kriging. In order to derive a wide-band acoustic impedance --similar to the one can be derived from a sonic log- from a band-limited reflection seismogram, we need to recover missing low- and high-frequency information of the seismic trace. For that Purpose we use the autoregressive method.
Singular Cell Integral of Green's tensor in Integral Equation EM Modeling
Song Yoonho ; Chung Seung-Hwan ;
Geophysics and Geophysical Exploration, volume 3, issue 1, 2000, Pages 13~18
We describe the concept of the singularity in the integral equation of electromagnetic (EM) modeling in comparison with that in the integral representation of electric fields in EM theory, which would clarify the singular integral problems of the Green's tensor. We have also derived and classified the singular integrals of the Green's tensors in 3-D, 2.5-D and 2-D as well as in the thin sheet integral equations of the EM scattering problem, which have the most important effect on the accuracy of the numerical solution of the problems.
Frequency Characteristics of Shallow Seismic Reflection Data - Dogye, Samchuck, Kangwon
Ko, Kwang-Beom ; Lee, Doo-Sung ;
Geophysics and Geophysical Exploration, volume 3, issue 1, 2000, Pages 19~24
Seismic reflection data was obtained by using 28 and 100 Hz geophones at the ground subsidence sites in an old coal mine area. Frequency spectrum of the geophone analyzed with offset revealed that 1) In the near offset (
), the signals in the 100 Hz geophone data contains higher frequency components (up to 300 Hz) than that of the 28 Hz (<200 Hz), 2) In the intermediate offset (
), although the 28 Hz geophone data showed very similar frequency characteristics as the near offset data, the 100Hz geophone data seemed to be contaminated by noise at high frequency zone (>200 Hz). In the far offset (
), the signals in both the 28 and 100 Hz geophone data are attenuated to noise level at high frequency Bone more than 150 Hz.
Development of Geophysical Data Management System
Lee, Tai-Sup ; Hwang, Hak-Soo ; Sun, Hee-Duck ; Koo, Sung-Bon ; Song, Yaung-Soo ;
Geophysics and Geophysical Exploration, volume 3, issue 1, 2000, Pages 25~32
The geophysical data management system was developed to meet both the increasing demands of geophysical data in the practical application of civil engineering, underground water survey, and environmental problems and needs for digital archive and quality control of geophysical data. The system for a data manager is developed under Client/Server (C/S) environment. This manager system is characterized by a relational geophysical database system using MS SQL-server, standardization of geophysical data format, the development of C/S interface program for Windows environment, and the development of transfer program module for the searched data. The system developed for a general user under the internet environment is characterized by Web service (URL:http//geophy.kigam.re.kr) and the development of plug-in module to visualize geophysical image data.