Go to the main menu
Skip to content
Go to bottom
REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Geophysics and Geophysical Exploration
Journal Basic Information
Journal DOI :
Korean Society of Earth and Exploration Geophysicists
Editor in Chief :
Volume & Issues
Volume 5, Issue 4 - Nov 2002
Volume 5, Issue 3 - Aug 2002
Volume 5, Issue 2 - May 2002
Volume 5, Issue 1 - Feb 2002
Selecting the target year
Time-lapse 3-dimensional Seismic Study to Evaluate the Effect of Ground Reenforcement
Lee, Doo-Sung ;
Geophysics and Geophysical Exploration, volume 5, issue 3, 2002, Pages 141~144
Three-dimensional seismic data, recorded with an interval of one year, indicate a velocity changes in the medium at the near surface. During that period of a year, the ground reinforcement work has been conducted at the railroad base in the study area. The time-thickness to the first reflector of the two data were picked and compared. The result showed that the velocity of the medium decreased at large part of the study area; however, no velocity decrease at the railroad base.
Static Correction of Land 3D Seismic Data
Sheen Dong-Hoon ; Park Jae-Woo ; Ji Jun ; Lee Doo-Sung ;
Geophysics and Geophysical Exploration, volume 5, issue 3, 2002, Pages 145~149
The static correction, which is classified into refraction based static correction and reflection based residual static correction, removes distortions caused by irregularities of thickness or velocity in near-surface. Generally, refraction statics is a time consuming process because of high dependence on the interpreter's analysis. Therefore, for huge 3D seismic data, automatic static correction which minimizes the interpreter's analysis is required. In this research, we introduce an efficient method of refraction static correction for land 3D seismic survey.
Development of a GUI Crosswell Seismic Tomography Software on Linux
Sheen Dong-Hoon ; Ko Kwang Beom ; Park Jae-Woo ; Ji Jun ; Lee Doo-Sung ;
Geophysics and Geophysical Exploration, volume 5, issue 3, 2002, Pages 150~156
In this study, a software for crosswell seismic tomography is developed. The software consists of first arrival picking and adjusting module, crosswell traveltime tomography module, and imaging module. This software allows saying the picked first arrival times into the header of seismic data, and using this data directly to the input of crosswell seismic tomography. With an imaging module, velocity structures and ray path can be imaged directly from the output of the tomography module. Because it is developed on the basis of the SU under the Linux and the GUI environment for user, this software can be carried out directly the first arrival picking, inversion and tomogram for crosswell tomography data in the field. Therefore, this software can be improved the applicability of site investigation by tomography method.
Recovery of Lithospheric Magnetic Component in the Satellite Magnetometer Observations of East Asia
Kim, Jeong-Woo ;
Geophysics and Geophysical Exploration, volume 5, issue 3, 2002, Pages 157~168
Improved procedures were implemented in the production of the lithospheric magnetic anomaly map from Magsat satellite magnetometer data of East Asia between
. Procedures included more effective selection of the do·it and dawn tracks, ring current correction, and separation of core field and external field effects. External field reductions included an ionospheric correction and pass-by-pass correlation analysis. Track-line noise effects were reduced by spectral reconstruction of the dusk and dawn data sets. The total field magnetic anomalies were differentially-reduced-to-the-pole to minimize distortion s between satellite magnetic anomalies and their geological sources caused by corefield variations over the study area. Aeromagnetic anomalies were correlated with Magsat magnetic anomalies at the satellite altitude to test the lithospheric veracity of anomalies in these two data sets. The aeromagnetic anomalies were low-pass filtered to eliminate high frequency components that may not be shown at the satellite altitude. Although the two maps have a low CC of 0.243, there are many features that are directly correlated (peak-to-peak and trough-to-trough). The low CC between the two maps was generated by the combination of directly- and inversely-correlative anomaly features between them. It is very difficult to discriminate directly, inversely, and nully correlative features in these two anomaly maps because features are complicatedly correlated due to the depth and superposition of the anomaly sources. In general, the lithospheric magnetic components were recovered successfully from satellite magnetometer observations and correlated well with aeromagnetic anomalies in the study area.
Weighted-averaging Finite-element Method for Scalar Wave Equation in the Frequency Domain
Hyun Hye-Ja ; Suh Jung-Hee ; Min Dong-Joo ;
Geophysics and Geophysical Exploration, volume 5, issue 3, 2002, Pages 169~177
We develop the weighted-averaging finite-element method which uses four kinds of element sets. By constructing global stiffness and mass matrices for four kinds of element sets and then averaging them with weighting coefficients, we obtain a new global stiffness and mass matrix. With the optimal weighting coefficients minimizing grid dispersion and grid anisotropy, we can reduce the number of grid points required per wavelength to 4 for a
upper limit of error. We confirm the accuracy of our weighted-averaging finite-element method through accuracy analyses for a homogeneous and a horizontal-layer model. By synthetic data example, we reconfirm that our method is more efficient for simulating a geological model than previous finite-element methods.
Subsurface Imaging using Headwave Stacking
Park Jung-Jae ; Ko Seung-Won ; Shin Chang-Soo ; Suh Jung-Hee ;
Geophysics and Geophysical Exploration, volume 5, issue 3, 2002, Pages 178~184
For economy and convenience, seismic refraction survey is widely used in surveying for large civil engineering work. The purpose of this study is to obtain the numerical responses of various models using Kirchhoff migration, and to analyze its application to the real data processing. Synthetic traveltime curve was calculated by vidale's algorithm, and various models such as 2 or 3 layer model and irregular topography model are tested to simulate the response of real structure. In order to compare the effect of initial velocity model, true velocity models, inversion results by tomography, smooth velocity models are used as an initial guess. The responses of model data show that the algorithm of this study is more sensitive to initial velocity model than the reflection survey, so choosing a suitable initial velocity model will be the most important thing in real data processing.
Imaging of Ground Penetrating Radar Data Using 3-D Kirchhoff Migration
Cho, Dong-Ki ; Suh, Jung-Hee ; Choi, Yoon-Kyoung ;
Geophysics and Geophysical Exploration, volume 5, issue 3, 2002, Pages 185~192
We made a study of 3-D migration which could precisely image data of GPR (Ground Penetrating Radar) applied to NDT (Non-Destructive Test) field for the inspection of structural safety. In this study, we obtained 3-D migrated images of important targets in structuresurvey (e.g. steel pipes, cracks) by using 3-D Kirchhoff prestack depth migration scheme developed for seismic data processing. For a concrete model consisting of steel pipe and void, the targets have been well defined with opposite amplitude according to the parameters of the targets. And migrated images using Parallel-Broadside array (XX configuration) have shown higher resolution than those using Perpendicular-Broadside array (YY configuration) when steel pipes had different sizes. Therefore, it is required to analyze the migrated image of XX configuration as well as that of general YY configuration in order to get more accurate information. As the last stage, we chose a model including two steel pipes which cross each other. The upper pipe has been resolved clearly but the lower has been imaged bigger than the model size due to the high conductivity of the upper steel.
A Source Static Correction Algorithm in Crosswell Tomography
Ji Jun ;
Geophysics and Geophysical Exploration, volume 5, issue 3, 2002, Pages 193~198
In crosswell ray tomography, the resultant velocity structure could be affected by source static, first-arrival-time picking errors, convergence to a local minimum due to an inappropriate initial velocity model and etc. In the paper, I propose an algorithm that automatically correct the souce static among these error-prone factors. The algorithm automatically corrects source static using the picking times' differences along the source direction. The application of the algorithm to real data produces a quite satisfactory result. Tile algorithm seems to be helpful for users to apply the souce static correction consistently and to acquire accurate velocity structure.
Negative Apparent Resistivity in Resistivity Method
Cho In-Ky ; Kim Jung-Ho ; Chung Seung-Hwan ; Suh Jung-Hee ;
Geophysics and Geophysical Exploration, volume 5, issue 3, 2002, Pages 199~205
In the resistivity method, the potential difference between two grounded electrodes is measured and this can be positive or negative. The apparent resistivity and the potential difference have the same polarity. Since the electric field is the gradient of the potential, the polarity of the potential difference depends on the direction of the electric field. If the direction of the vector connecting two grounded electrodes is the same to that of the electric field, the measured potential difference and the apparent resistivity become positive. If the opposite is the case, they become negative. In general, the primary electric field and the vector connecting two potential electrodes have the same direction in a surface resistivity method. In this case, the measured potential difference is always positive because the primary electric field is greater than the secondary field. Therefore, the apparent resistivity is always positive if noise is free and topography is flat. The secondary field component, however, can be greater than the primary field component along the vector connecting two potential electrodes in the cross-hole resistivity method. Furthermore, if the secondary electric field and the vector connecting two potential electrodes have an opposite direction, the apparent resistivity become negative. Consequently, the apparent resistivity may be negative in the region where the primary electric field component along the vector connecting two potential electrodes is very small.
FEM Electrical Resistivity Modeling in Cylindrical Coordinates
Choi Wonseok ; Kim Jung-Ho ; Park KwonGyu ; Kim Hak-Soo ; Suh Jung-Hee ;
Geophysics and Geophysical Exploration, volume 5, issue 3, 2002, Pages 206~216
The finite element method (FEM), a powerful numerical modeling tool for solving various engineering problems, is frequently applied to three-dimensional (3-D) modeling thanks to its capability of discretizing and simulating the shape of model with finite number of elements. Considering the accuracy of the solution and computing time in modeling of engineering problems, it is preferable to construct physical continuity and simplify mesh system. Although there exist systematic mesh generation systems for arbitrary shaped model, it is hard to model a simple cylinder in terms of 3-D coordinate system especially in the vicinity of the central axis. In this study I adopt cylindrical coordinate system for modeling the 3-D model space and define the origin of the coordinates with mathematically clear coordinate transformation. Since we can simulate the whole space with hexahedral elements, the cylindrical coordinate system is effective in handling the 3-D model structure. The 3-D do resistivity modeling scheme developed in this study provides basie principle for borehole-to-surface resistivity survey, which can be a useful tool for the application to environmental problem.