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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Geophysics and Geophysical Exploration
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Journal DOI :
Korean Society of Earth and Exploration Geophysicists
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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
Comparative Study on Separation Method of Attenuation Quality Factor
Chung, Tae-Woong ;
Geophysics and Geophysical Exploration, volume 12, issue 4, 2009, Pages 281~288
Using analytical method, intrinsic absorption and scattering attenuation was lately separated from total quality factor
on the seismic data of Korean Peninsula. However, we should use numerical method rather than the analytical method to consider depth dependent structure of scattering. The direct simulation Monte Carlo (DSMC) method, as a kind of the numerical method, is good option due to its extended availability from 1 to 3-dimensional model; but there is few study to use it. In this paper, we introduced the analytical method and the DSMC method, and compared the results of the two analysis applied to the isotropic scattering model. While the scattering attenuation coefficients
are identical, the intrinsic absorption coefficients
for the analytical method are larger than those for DSMC method and have large errors. In addition, the
by the previous studies show closer to DSMC method than analytical method.
Optimal Rejection of Sea Bottom, Peg-leg and Free-surface Multiples for Multichannel Seismic Data on South-eastern Sea, Korea
Cheong, Snons ; Koo, Nam-Hyung ; Kim, Won-Sik ; Lee, Ho-Young ; Shin, Won-Chul ; Park, Keun-Pil ; Kim, Jin-Ho ;
Geophysics and Geophysical Exploration, volume 12, issue 4, 2009, Pages 289~298
Optimal data processing parameters were designed to attenuate multiples in seismic data acquired in the south-eastern area of the East Sea, in 2008. Bunch of multiples caused by shallow sea water depth were perceived periodically up to two way travel time of 1,750 ms at every 250 ms over seismic traces. We abbreviated sea bottom multiple as SBM, Peg-leg multiple as PLM, and free-surface multiple as FSM. To attenuate these multiples, seismic data processing flow was constructed including NMO, stack, minimum phase predictive deconvolution filter and wave equation multiple rejections (WEMR). Prevalent multiples were suppressed by predictive deconvolution and remaining multiples were attenuated by WEMR. We concluded that combining deconvolution with WEMR was effective to a seismic data of study area. Derived parameter can be applied to the seismic data processing on adjacent survey area.
Site Investigation for Pilot Scale
Sequestration by Magnetotelluric Surveys in Uiseong, Korea
Lee, Tae-Jong ; Han, Nu-Ree ; Ko, Kwang-Beom ; Hwang, Se-Ho ; Park, Kwon-Gyu ; Kim, Hyung-Chan ; Park, Yong-Chan ;
Geophysics and Geophysical Exploration, volume 12, issue 4, 2009, Pages 299~308
A magentotelluric (MT) survey at the Uiseong area has been performed for the site investigation of pilot scale
sequestration. The purpose of the MT survey is to delineate deeply extended fracture systems that can act as a leakage path of injected
Plume. Since the target area is extremely noisy in electromagentic sense, low frequency data below 1 Hz cannot be used for inversion. Two- and three-dimensional interpretation of the MT data showed a very clear conductive anomaly, which has the direction of
and is extended roughly down to 1.6 km. It have the same direction with the strike-slip faults, the Gaeum and Geumcheon Faults. On the contrary, the eastern part of the survey area shows relatively homogeneous to the depth of 2 km though some small fractures at shallow depths can be found. Test drilling and high-definition borehole surveys should be followed at the eastern part of the survey area and hydraulic fracturing is required for injection of
, because mean porosity of the sedimetary rock in the area is only 1.47%.
Geostatistical Integration of Multi-Geophysical Data Measured at Different Ranges
Oh, Seok-Hoon ;
Geophysics and Geophysical Exploration, volume 12, issue 4, 2009, Pages 309~315
Integrated interpretation of multi-geophysical data has been continuously used in terms that it has provided more confident information than the result from single-geophysical data. Especially, geostatistical integration has its own superiority that it is possible to deal with spatial characteristics as well as physical properties of survey data and the process of integration is clear. This paper further extends the previous work of geostatistical inversion for integrated interpretation. In this paper, we propose a new way of dealing with the case that the multi-geophysical data do not share the measurement range. According to the geostatistical kriging, the closer between the measurement points, the smaller kriging variance we get, and vice versa. We used this spatial properties as a weighting value to the process of geostatistical inversion for the geophysical data integration. An objective way to integrate different kinds of geophysical data measured at different ranges is provided with this algorithm.
Epicenter Estimation Using Real-Time Event Packet of Quanterra digitizer
Lim, In-Seub ; Sheen, Dong-Hoon ; Shin, Jin-Soo ; Jung, Soon-Key ;
Geophysics and Geophysical Exploration, volume 12, issue 4, 2009, Pages 316~327
A standard for national seismological observatory was proposed on 1999. Since then, Quanterra digitizer has been installed and is operating on almost all of seismic stations which belong to major seismic monitoring organizations. Quanterra digitizer produce and transmit real-time event packet and data packet. Characteristics of event packet and arrival time of each channel's data packet on data center were investigated. Packet selection criteria using signal to noise ratio (hereafter SNR) and signal period from real-time event packet based on 100 samples per second (hereafter sps) velocity data were developed. Estimation of epicenter using time information of the selected event packet were performed and tested. A series of experiment show that event packets were received approximately 3~4 second earlier than data packets and the number of event packet was only 0.3% compare to data packets. Just about 5% against all of event packets were selected as event packet were related P wave of real earthquake. Using the selected event packets we can estimate an epicenter with misfit less than 10 km within 20 sec for local earthquake over magnitude 2.5.
Electrical Resistivity of Cylindrical Cement Core with Successive Substitution by Electrolyte of Different Conductivity
Lee, Sang-Kyu ; Lee, Tae-Jong ;
Geophysics and Geophysical Exploration, volume 12, issue 4, 2009, Pages 328~337
To investigate the relation between pore fluid conductivity and bulk resistivity of a rock sample it is assumed that electrolyte solution perfectly substitute the pore fluid that occupied the pore space within the sample in general. In this study, it is investigated that how much can the electrolyte solution substitute the pore fluid by repeating the same saturation process. Four kinds of NaCl solutions of 8, 160, 3200, 64000
/cm are used. The saturation process has repeated four times for each electrolyte in increasing conductivity order first then four times each in decreasing order. The more the saturation process repeated with the same electrolyte, the more electrolyte solution substitute the pore fluid. Geometric mean of bulk resistivity in increasing and decreasing orders with the same electrolyte solution is assumed to be mostly close to the bulk resistivity with perfect substitution. Bulk resistivity measurements for both increasing and decreasing order differs within 10% to the geometric mean when repeating the saturation process 4 times while maximum 40% difference is observed when single saturation process for each electrolyte solution with increasing order. The modified parallel resistant model can generally represent the relations between pore fluid resistivity and bulk resistivity in the experiment, but more experimental data with various rock samples with different porosity is needed to generalize the model.
Integrated Application of GPR, IE and IR Methods to Detection of the Rear Cavity of Concrete
Noh, Myung-Gun ; Oh, Seok-Hoon ; Jang, Bong-Seok ;
Geophysics and Geophysical Exploration, volume 12, issue 4, 2009, Pages 338~346
Integrated analysis of GPR, impact echo (IE) and impulse response (IR) was performed to detect the rear cavity of concrete for a test-bed which was made with the same scale and component ratio to the real concrete structure. The test-bed was designed to be capable of observing various response reflecting the existence of iron reinforcing bar and cavity. GPR survey did not clearly resolve the existence of the cavity, although distinguishable responses were observed in the presence of the cavity. In contrast, IE and IR method showed distinct responses, indicating the existence of the cavity. Finally, integrated application of the three methods makes it possible to exactly identify the location of the cavity, although the iron reinforcing bar made a little variation of response.
Smoothing Effect in X-ray Microtomogram and Its Influence on the Physical Property Estimation of Rocks
Lee, Min-Hui ; Keehm, Young-Seuk ;
Geophysics and Geophysical Exploration, volume 12, issue 4, 2009, Pages 347~354
Physical properties of rocks are strongly dependant on details of pore micro-structures, which can be used for quantifying relations between physical properties of rocks through pore-scale simulation techniques. Recently, high-resolution scan techniques, such as X-ray microtomography and high performance computers make it possible to calculate permeability from pore micro-structures of rocks. We try to extend this simulation methodology to velocity and electrical conductivity. However, the smoothing effect during tomographic inversion creates artifacts in pore micro-structures and causes inaccurate property estimation. To mitigate this artifact, we tried to use sharpening filter and neural network classification techniques. Both methods gave noticeable improvement in pore structure imaging and accurate estimation of permeability and electrical conductivity, which implies that our method effectively removes the smoothing effect in pore structures. However, the calculated velocities showed only incremental improvement. By comparison between thin section images and tomogram, we found that our resolution is not high enough, and it is mainly responsible for the inaccuracy in velocity despite the successful removal of the smoothing effect. In conclusion, our methods can be very useful for pore-scale modeling, since it can create accurate pore structure without the smoothing effect. For accurate velocity estimation, the resolution of pore structure should be at least three times higher than that for permeability simulation.
Mobile Robot Based Down-Scaled Mineral Resources Exploration Test System
Yu, Son-Cheol ; Jung, Hyun-Key ; Yoon, Joong-Sun ; Pyo, Ju-Hyun ; Cho, Sung-Ho ; Oh, Dong-Moon ; Kang, Dong-Joung ;
Geophysics and Geophysical Exploration, volume 12, issue 4, 2009, Pages 355~360
This paper presents mobile robot based down-scale mineral resources exploration test system for the USN (Ubiquitous Sensor Network) based exploration. The system emulates the actual exploration environment. Underneath the metal free test plate, a metal object is attached. A magneto-meter mounted mobile robot runs around on the plate to find the metal. The measured magneto-meter values are transferred to the host PC via wireless network. The system enables to improve the reliability of simulation as well as to help efficient exploration system design. Metal-detecting experiments were carried out to illustrate the efficiency of the proposed system.
Primary Solution Evaluations for Interpreting Electromagnetic Data
Kim, Hee-Joon ; Choi, Ji-Hyang ; Han, Nu-Ree ; Song, Yoon-Ho ; Lee, Ki-Ha ;
Geophysics and Geophysical Exploration, volume 12, issue 4, 2009, Pages 361~366
Layered-earth Green's functions in electormagnetic (EM) surveys play a key role in modeling the response of exploration targets. They are computed through the Hankel transforms of analytic kernels. Computational precision depends upon the choice of algebraically equivalent forms by which these kemels are expressed. Since three-dimensional (3D) modeling can require a huge number of Green's function evaluations, total computational time can be influenced by computational time for the Hankel transform evaluations. Linear digital filters have proven to be a fast and accurate method of computing these Hankel transforms. In EM modeling for 3D inversion, electric fields are generally evaluated by the secondary field formulation to avoid the singularity problem. In this study, three components of electric fields for five different sources on the surface of homogeneous half-space were derived as primary field solutions. Moreover, reflection coefficients in TE and TM modes were produced to calculate EM responses accurately for a two-layered model having a sea layer. Accurate primary fields should substantially improve accuracy and decrease computation times for Green's function-based problems like MT problems and marine EM surveys.
Manufacture of a Sea Surface Recording Device for the Shallow Seismic Refraction Survey
Jou, Hyeong-Tae ; Kim, Han-Joon ; Park, Gun-Tae ; Lee, Gwang-Hoon ; Jang, Nam-Do ; Jung, Baek-Hoon ;
Geophysics and Geophysical Exploration, volume 12, issue 4, 2009, Pages 367~369