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 14, Issue 4 - Nov 2011
Volume 14, Issue 3 - Aug 2011
Volume 14, Issue 2 - May 2011
Volume 14, Issue 1 - Feb 2011
Selecting the target year
A Scheme for Computing Primary Fields in Modeling of Marine Controlled-Source Electromagnetic Surveys
Kim, Hee-Joon ;
Geophysics and Geophysical Exploration, volume 14, issue 3, 2011, Pages 185~190
In marine controlled-source electromagnetic (CSEM) modeling, it may be difficult to evaluate primary fields accurately using conventional linear filters because they decay very rapidly with distance. However, since there exists a closed-form solution to the Hankel transform in TM mode for a homogeneous half space, we can assess the accuracy of linear filters for evaluating the Hankel transform. As a result, only nine out of 36 source-receiver pairs show that EM fields decrease linearly in semi-log scale with an increase of source-receiver distance, while EM fields are either 0 or not reduced significantly due to an effect of the air layer. There also exist closed-form solutions for the nine pairs, and the others can be evaluated accurately with a relatively short filter. This paper proposes a method which uses closed-form solutions for TM-mode Hankel transforms and a filter with 61 coefficients for TE-mode ones.
Reverse-time Migration for VTI and TTI Media
Kwak, Na-Eun ; Min, Dong-Joo ; Bae, Ho-Seuk ;
Geophysics and Geophysical Exploration, volume 14, issue 3, 2011, Pages 191~202
Reserve-time migration (RTM) using a two-way wave equation is one of the most accurate migration techniques. RTM has been conducted by assuming that subsurface media are isotropic. However, anisotropic media are commonly encountered in reality. Conventional isotropic RTM may yield inaccurate results for anisotropic media. In this paper, we develop RTM algorithms for vertical transversely isotropic media (VTI) and tilted transversely isotropic media (TTI). For this, the pseudo-acoustic wave equations are used. The modeling algorithms are based on the high-order finite-difference method (FDM). The RTM algorithms are composed using the cross-correlation imaging condition or the imaging condition using virtual sources. By applying the developed RTM algorithms to the Hess VTI and BP TTI models, we could obtain better images than those obtained by the conventional isotropic RTM.
An Introduction to Time-lapse Seismic Reservoir Monitoring
Nam, Myung-Jin ; Kim, Won-Sik ;
Geophysics and Geophysical Exploration, volume 14, issue 3, 2011, Pages 203~213
Time-lapse seismic surveys make repeated seismic surveys at different stages of oil production of a hydrocarbon reservoir to monitor changes in reservoir like fluid saturation. Since the repeatable surface seismic measurements can identify fluid types and map fluid saturations, oil and gas companies can make much more informed decision during not only production but also drilling and development. If time-lapse seismic surveys compare 3D seismic surveys, the time-lapse surveys are widely called as 4D seismic. A meaningful time-lapse interpretation is based on the repeatability of seismic surveys, which mainly depends on improved positioning and reduced noise (if surveys were designed properly through a feasibility study). The time-lapse interpretation can help oil and gas companies to maximize oil and gas recovery. This paper discusses about time-lapse seismic surveys mainly focused on feasibility, repeatability, data processing and interpretation.
Frequency-domain Waveform Inversion using Residual-selection Strategy
Son, Woo-Hyun ; Pyun, Suk-Joon ; Kwak, Sang-Min ;
Geophysics and Geophysical Exploration, volume 14, issue 3, 2011, Pages 214~219
We perform the frequency-domain waveform inversion based on the residual-selection strategy. In the residual-selection strategy, we classify time-domain residual wavefields into several groups according to the order of absolute amplitudes. Because the residual wavefields are normalized after regularization of the gradient directions within each group, the residual-selection strategy plays a role in enhancing the small-amplitude wavefields, which contributes to improving the deep parts of inverted subsurface images. After classifying residuals in the time domain, they are transformed to the frequency domain. Waveform inversion is performed in the frequency domain using the back-propagation technique which has been popularly used in reverse-time migration. The residual-selection strategy is applied to the SEG/EAGE salt and IFP Marmousi models. Numerical results show that the residual-selection strategy yields better results than the conventional frequency-domain waveform inversion.
Application of Displacement-Vector Objective Function for Frequency-domain Elastic Full Waveform Inversion
Kwak, Sang-Min ; Pyun, Suk-Joon ; Min, Dong-Joo ;
Geophysics and Geophysical Exploration, volume 14, issue 3, 2011, Pages 220~226
In the elastic wave equations, both horizontal and vertical displacements are defined. Since we can measure both the horizontal and vertical displacements in field acquisition, these displacements compose a displacement vector. In this study, we propose a frequency-domain elastic waveform inversion technique taking advantage of the magnitudes of displacement vectors to define objective function. When we apply this displacement-vector objective function to the frequency-domain waveform inversion, the inversion process naturally incorporates the back-propagation algorithm. Through the inversion examples with the Marmousi model and the SEG/EAGE salt model, we could note that the RMS error of the solution obtained by our algorithm decreased more stably than that of the conventional method. Particularly, the density of the Marmousi model and the low-velocity sub-salt zone of the SEG/EAGE salt model were successfully recovered. Since the gradient direction obtained from the proposed objective function is numerically unstable, we need additional study to stabilize the gradient direction. In order to perform the waveform inversion using the displacementvector objective function, it is necessary to acquire multi-component data. Hence, more rigorous study should be continued for the multi-component land acquisition or OBC (Ocean Bottom Cable) multi-component survey.
Imaging Fractures by using VSP Data on Geothermal Site
Lee, Sang-Min ; Byun, Joong-Moo ; Song, Ho-Cheol ; Park, Kwon-Gyu ; Lee, Tae-Jong ;
Geophysics and Geophysical Exploration, volume 14, issue 3, 2011, Pages 227~233
Attention has been focused on geothermal energy as an alternative energy because it is continuously operable without external supply. Most of geothermal anomalies in Korea are related to deep circulation of groundwater through a fracture system in granite area. Therefore it is very important to understand the distribution of the fracture system which is the main channel of ground water. In this research, we constructed the velocity models with a fracture system and the layered sediments, respectively, and generated synthetic data sets with them to verify the presented vertical seismic profiling (VSP) preprocessing scheme. We compared the results from conventional VSP preprocessing flow to those from VSP preprocessing flow considering fracture system. We noticed that the preprocessing flow considering fracture system retains more sufficient signal including down-going wave than conventional preprocessing. In addition, we applied 3D VSP prestack phase screen migration to the preprocessed reversed VSP (RVSP) data from Seokmo Island so that we were able to image fracture structure of the geothermal site in Seokmo Island.
Multicomponent RVSP Survey for Imaging Thin Layer Bearing Oil Sand
Jeong, Soo-Cheol ; Byun, Joong-Moo ;
Geophysics and Geophysical Exploration, volume 14, issue 3, 2011, Pages 234~241
Recently, exploration and development of oil sands are thriving due to high oil price. Because oil sands reservoir usually exists as a thin layer, multicomponent VSP, which has the advantage of the high-resolution around the borehole, is more effective than surface seismic survey in exploring oil sand reservoir. In addition, prestack phase-screen migration is effective for multicomponent seismic data because it is based on an one-way wave equation. In this study, we examined the applicability of the prestack phase-screen migration for multicomponent RVSP data to image the thin oil sand reservoir. As a preprocessing tool, we presented a method for separating P-wave and PS-wave from multicomponent RVSP data by using incidence angle and rotation matrix. To verify it, we have applied the developed wavefield separation method to synthetic data obtained from the velocity model including a horizontal layer and dipping layers. Also, we compared the migrated image by using P-wave with that by using PS-wave. As a result, the PS-wave migrated image has higher resolution and wide coverage than P-wave migrated image. Finally, we have applied the prestack phase-screen migration to the synthetic data from the velocity model simulating oil sand reservoir in Canada. The results show that the PS-wave migrated image describe the top and bottom boundaries of the thin oil sand reservoir more clearly than the P-wave migrated image.
A Study of Multiple Scattering Model by Analytic Method for Southeastern Korea
Chung, Tae-Woong ;
Geophysics and Geophysical Exploration, volume 14, issue 3, 2011, Pages 242~248
By applying analytic method to the uniform model, the intrinsic and scattering quality factor (
) was separated for the southeastern part of Korean Peninsula. The Multiple Lapse Time Window Analysis method was used to fit theoretical values with observations obtained 759 earthquake data. While previous study for the Korean Peninsula showed very low
reflecting inactive seismicity, southeastern Korea exhibited relatively high
values interpreted as higher seismicity than the other region in the peninsula.
Comparative Study on Coda Attenuation of the Southeastern Korean Peninsula
Chung, Tae-Woong ; Choi, Soo-Hyun ;
Geophysics and Geophysical Exploration, volume 14, issue 3, 2011, Pages 249~253
Based on intrinsic and scattering quality factor (
) obtained from the seismic data of the southeastern Korean Peninsula, the expected coda quality factor (
) was theoretically calculated using multiple scattering model, and was compared with other quality factors such as
, and observed
obtained by single scattering model. While the
values are typically comparable to the
values are different from the
values except for the higher frequency. Future works require to consider depth-dependent attenuation.
Estimation of Earthquake Magnitude Using High-Frequency Energy Radiation Duration: Application to Regional Earthquakes
Yun, Won-Young ; Park, Sun-Cheon ; Jeon, Young-Soo ;
Geophysics and Geophysical Exploration, volume 14, issue 3, 2011, Pages 254~260
We studied magnitude determination method using high-frequency energy radiation duration to calculate rapidly magnitude of large earthquakes that occurred around Japan. Fourteen earthquakes were analyzed using Korea Meteorological Administration (KMA) data. We calculated duration of high-frequency energy radiation with 2~4 Hz band pass filter at each data and estimated magnitude. As a result, duration becomes longer as magnitude becomes larger and the magnitude estimated using regional earthquake data are similar to that using teleseismic data. Therefore when an earthquake occurs around Japan we will be able to estimate the magnitude in a relatively short time using KMA data and it may be possible to determine if the earthquake is large enough to produce tsunami.