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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 12, Issue 4 - Nov 2009
Volume 12, Issue 3 - Aug 2009
Volume 12, Issue 2 - May 2009
Volume 12, Issue 1 - Feb 2009
Selecting the target year
P-wave Velocity Anisotropy in the Upper Crust of the Southern Korean Peninsula Using Seismic Signals from Large Explosions
Hong, Myung-Ho ; Kim, Ki-Young ;
Geophysics and Geophysical Exploration, volume 12, issue 3, 2009, Pages 225~232
As part of seismic experiments investigating crustal velocity structures of the Korean peninsula, permanent (fixed) seismographs of the Korea Meteorological Administration (KMA) network recorded seismic signals from four and eight large explosions in Korean Crustal Research Team (KCRT) profiles shot in 2004 and 2008, respectively. Among the seismograms recorded by 43 velocity sensors and 103 accelerometers at KMA stations distributed throughout the southern Korean Peninsula, 156 records with epicentral distances less than 120 km and high signal-to-noise ratios were analyzed to determine velocity anisotropy of the Pg phase. Relative elevation corrections of -101.6 to 105.3 ms were made using velocity information derived from the 2004 KCRT profile data and differences in elevation between the permanent KMA stations and the temporary stations in the KCRT profiles at the same source-receiver offsets. To remove site effects, receiver-station corrections of -89.6 to 192.2 ms were additionally made to the KMA station data by subtracting the average differences in traveltimes between KMA stations and portable stations at the same offsets for all available shots with different azimuths. With the exception of anomalously fast velocities along trends of the Chugaryeong fault zone and the Okchon fold belt and anomalously slow velocities in the regions of high terrestrial heat near Yeongduk and Ulsan, the analysis of crustal velocity anisotropy using the Pg phase indicates overall isotropy in the southern half of the Korean peninsula.
A Case Study on the Cross-Well Travel-Time Tomography Regulated by the Error in the Measurement of the First Arrival Time
Lee, Doo-Sung ;
Geophysics and Geophysical Exploration, volume 12, issue 3, 2009, Pages 233~238
An inversion method regulated by the error in the measurement of the first arrival time was developed, and we conducted a feasibility study by applying the method to a real cross-well seismic data. The inversion is a two-step regulation process; 1) derive the measurement error bound based on the resolution of the velocity image want to derive, and exclude the records whose picking error is larger than the error bound, 2) set the travel time residual to zero if the residual is less than the measurement error. This process prevents the trivial residuals are accumulated and contribute to the velocity-model update. Comparison of two velocity images, one by using all records and another by using the regulate inversion method, shows that the later velocity image exhibits less numerical artefacts, and it also indicates that, according to the Fermat's principle, the latter image is a more feasible velocity model.
Verification of Reinforcement with Grouting Materials in a Small Scale Reservoir Dike using Surface and Borehole Electrical Resistivity survey
Song, Sung-Ho ; Yong, Hwan-Ho ; Kim, Yang-Bin ;
Geophysics and Geophysical Exploration, volume 12, issue 3, 2009, Pages 239~245
To verify the reinforcing effect of grouting materials composed of colloid cement and ordinary portland cement on the water leakage region in a small scale dike, we performed a tubecasing method and applied surface electrical resistivity survey including electrical resistivity tomography (ERT) to find resistivity variation before and after grouting. Hydraulic conductivities after grouting show 10 times lower than those of before grouting. These variation indicates that the cement grout blocks the leakage pathway effectively. As the results of dipole-dipole resistivity survey along the dike, resistivity distribution after grouting did not represent noticeable spatial variation in time. Resistivity monitoring results at the dike with vertical electrical sounding (VES) showed that the region of decreasing apparent resistivity was occupied by the grout after grouting. Predicted resistivities from the inversion of ERT data well matched with results of VES at the same regions. From the ERT using check holes to inspect the effect of grouting, we could find that the ERT is quite effective to identify spatially the grout region in a dike.
Separation of Linear and Elliptic Particle Motions Using Multi-Component Complex Trace Analysis
Kim, Ki-Young ; Lee, So-Young ;
Geophysics and Geophysical Exploration, volume 12, issue 3, 2009, Pages 246~254
We developed a novel polarization filter to separate linearly polarized waves from elliptically polarized waves in an infinite homogeneous medium and at the free surface using methods of multicomponent complex trace analysis. Sensitivity to filter parameters were examined using synthetic data simulating particle motions in a homogeneous medium. For known amplitude ratios of horizontal-to-vertical components of P and Rayleigh waves
, respectively, the polarization filter precisely removes Rayleigh waves. Errors in the vertical and horizontal components of the filtered results increase with the ratio
and the product
, respectively. The vertical component errors also increase rapidly as the ratios of applied-to-modeled values of
) decrease, and are sensitive to
for small and large incidence angles, respectively. Errors of the filter are exactly the same for shear waves when the incidence angle is the supplementary of P-wave incidence angle.
Zero-Offset VSP Data Processing for Gas Hydrate-Bearing Sediments in East Sea
Kim, Myung-Sun ; Byun, Joong-Moo ; Yoo, Dong-Geun ;
Geophysics and Geophysical Exploration, volume 12, issue 3, 2009, Pages 255~262
Conventionally, vertical-seismic-profiling (VSP) survey that provides high-resolution information has mainly performed to obtain the exact depth of the gas hydrate-bearing sediment, which is one of the key factors in the development of the gas hydrate. In this study, we extracted interval velocities and created corridor stacks from the first domestic zero-offset VSP data, which were acquired with three component receivers at UBGH09 borehole in Ulleung Basin where gas hydrate exists. Then we compared the corridor stacks with a CMP stacked section from surface seismic data. First of all, we converted the signals recorded with three component receivers to true vertical and horizontal components by phase rotation, and divided the data into direct waves and reflected waves by wavefield separation processing. The trend of the interval velocity extracted from the zero-offset VSP was similar to that of the sonic log obtained at the same borehole. Because the interval velocity of the gas hydrate-bearing sediment above the BSR was high, and it decreased suddenly through the BSR, we could infer that free gas is accumulated below the BSR. The results of comparing the corridor stacks to the CMP stacked section of the surface seismic data showed that most reflection events agreed well with those in the surface CMP stacked section and that the phase-rotated VSP data corresponded better with the surface seismic data than the VSP data without phase rotation. In addition, by comparing a corridor stack produced from the transverse component with the CMP stacked section of the surface seismic data, we could identify PS mode-converted reflections in the CMP stacked section.
Comparative Study on Coda Attenuation of the Korean Peninsula
Chung, Tae-Woong ;
Geophysics and Geophysical Exploration, volume 12, issue 3, 2009, Pages 263~267
Recently intrinsic and scattering quality factor (
) was successfully separated from total quality factor (
) on the seismic data of the Korean Peninsula. From this result, we theoretically calculated the expected coda quality factor (
) based on multiple scattering model, and compared with other quality factors such as
, and observed coda quality factor (
) obtained by single scattering model. While the
values are comparable to the
values are close to the values of
except for the 24 Hz frequency. This results suggest that the assumption of uniform scatterer in the Korean Peninsula is unrealistic.
Feasibility of 3D Dipole-Dipole Electrical Resistivity Method to a Vein-Type Ore Deposit
Min, Dong-Joo ; Jung, Hyun-Key ; Lee, Hyo-Sun ; Park, Sam-Gyu ; Lee, Ho-Yong ;
Geophysics and Geophysical Exploration, volume 12, issue 3, 2009, Pages 268~277
Recently as the interest in the development of domestic ore deposits has increased, we can easily find some studies on exploration geophysics-based ore deposit survey in literature. Geophysical surveys have been applied to the investigation of both metallic and non-metallic ore deposit. For metallic ore-deposit survey, the 2D electrical resistivity method has been popularly used, because metallic mineral deposits are generally more conductive than surrounding media. However, geological structures are 3D rather than 2D structures, which may lead to misinterpretation in 2D inversion section. In this study, 3D effects are examined for several 3D structures such as a width-varying dyke model and a wedge-shaped model. We also investigate the effects of the direction of survey line. Numerical results show that the width-varying dyke model yields some low resistivity zone in the deep part, which is independent of real ore-body location. For the wedge-shaped model, even though the survey line is located apart from the ore body, the 2D inversion section still shows low resistivity zone in the deep part. When the survey line is not perpendicular to the strike of the ore body, the low resistivity zone is slightly broader but shallower than that obtained along the survey line perpendicular to the strike. For the survey lines that have an angle smaller than
with the strike of the ore body, the inversion results are totally distorted. From these results, we conclude that 2-D survey and interpretation can lead to misinterpretation of subsurface structures, which may be linked to economical loss. Eventually, we recommend to apply 3-D rather than 2-D electrical resistivity survey for ore-deposit survey.