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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Geophysics and Geophysical Exploration
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Korean Society of Earth and Exploration Geophysicists
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Volume & Issues
Volume 17, Issue 4 - Nov 2014
Volume 17, Issue 3 - Aug 2014
Volume 17, Issue 2 - May 2014
Volume 17, Issue 1 - Feb 2014
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Joint Electromagnetic Inversion with Structure Constraints Using Full-waveform Inversion Result
Jeong, Soocheol ; Seol, Soon Jee ; Byun, Joongmoo ;
Geophysics and Geophysical Exploration, volume 17, issue 4, 2014, Pages 187~201
DOI : 10.7582/GGE.2014.17.4.187
Compared with the separated inversion of electromagnetic (EM) and seismic data, a joint inversion using both EM and seismic data reduces the uncertainty and gives the opportunity to use the advantage of each data. Seismic fullwaveform inversion allows velocity information with high resolution in complicated subsurface. However, it is an indirect survey which finds the structure containing oil and gas. On the other hand, marine controlled-source EM (mCSEM) inversion can directly indicate the oil and gas using different EM properties of hydrocarbon with marine sediments and cap rocks whereas it has poor resolution than seismic method. In this paper, we have developed a joint EM inversion algorithm using a cross-gradient technique. P-wave velocity structure obtained by full-waveform inversion using plane wave encoding is used as structure constraints to calculate the cross-gradient term in the joint inversion. When the jointinversion algorithm is applied to the synthetic data which are simulated for subsea reservoir exploration, images have been significantly improved over those obtained from separate EM inversion. The results indicate that the developed joint inversion scheme can be applied for detecting reservoir and calculating the accurate oil and gas reserves.
A Study on the Characteristics of W-Mo Ore Deposit in Bayan-Onjuul, Mongolia Using Magnetic Data
Park, Gyesoon ; Lee, Bum Han ; Kim, In-Joon ; Heo, Chul-Ho ;
Geophysics and Geophysical Exploration, volume 17, issue 4, 2014, Pages 202~208
DOI : 10.7582/GGE.2014.17.4.202
KIGAM (Korea Institute of Geoscience and Mineral Resources) and MRAM (Mineral Resources Authority of Mongolia) performed joint survey on Bayan-Onjuul W-Mo mineralized area. Following the survey, we carried out magnetic survey. W-Mo occurrences are located with keeping a certain distance from the northern boundary of granite which has higher magnetic susceptibility values. Also, the 3D imaging results of magnetic inversion show that granite bodies are extended to the W-Mo occurrence areas from the deep main body with decreasing of susceptibility. The results of magnetic data analysis are well matched with the general characteristics of ore solution involved with W mineralization. The further study about the hidden ore deposits which have similar spatial relationship between granite and known WMo occurrences are necessary to improve the economic feasibility.
Potential Mapping of Moisan area Using SIP and 3D Geological Modeling
Park, Gyesoon ; Park, Samgyu ; Son, Jeong-Sul ; Kim, Changryol ; Cho, Seong-Jun ;
Geophysics and Geophysical Exploration, volume 17, issue 4, 2014, Pages 209~215
DOI : 10.7582/GGE.2014.17.4.209
In order to develop a new mineral exploration technique, a study was carried out about the potential mapping of Moisan area using SIP (Spectral Induced Polarization) data. The SIP inversion results were classified according to the geological regions, and the distribution characteristics of resistivity and phase values of SIP data were analyzed at the ore region. Based on the characteristics of SIP of ore bodies, we performed 3D potential mapping of Moisan area. The analyzed potential map was verified using that the locations and patterns of high potential regions of the results are well matched with those of the known ore bodies. If we get the higher spatial resolution SIP data, the potential mapping technique using SIP data can be effectively applied to the estimation of mining deposit.
Seismic Attribute Analysis of the Indicators for the Occurrence of Gas Hydrate in the Northwestern Area of the Ulleung Basin, East Sea
Kim, Kyoung Jin ; Yi, Bo Yeon ; Kang, Nyeon Keon ; Yoo, Dong Geun ; Shin, Kook Sun ; Cho, Young Ho ;
Geophysics and Geophysical Exploration, volume 17, issue 4, 2014, Pages 216~230
DOI : 10.7582/GGE.2014.17.4.216
Based on the interpretation of 3D seismic profiles acquired in the northwestern area of the Ulleung Basin, East Sea, the shallow sediments consist of five seismic units separated by regional reflectors. An anticline is present in the study area that documents activity of many faults. Bottom simulating reflectors are characterized by high RMS amplitude. Acoustic blanking with low RMS amplitude is distinctively recognized in the gas hydrate stability zone. Seismic attribute analysis shows that if gas hydrates are underlain by free gas, the high reflection strength and the low instantaneous frequency are displayed below the boundary between them. Whereas, if not, the reflection strength is low and instantaneous frequency is high continuously below the gas hydrate zone. Based on the spectral decomposition of the bottom simulating reflector, the high envelope at the specific high frequency range indicates the generation of the tuning effect due to the lower free gas content. Four models for the occurrence of the gas hydrate are suggested considering the slope of sedimentary layers as well as the presence of gas hydrate or free gas.
Velocity Model Building using Waveform Inversion from Single Channel Engineering Seismic Survey
Choi, Yeon Jin ; Shin, Sung Ryul ; Ha, Ji Ho ; Chung, Woo Keen ; Kim, Won Sik ;
Geophysics and Geophysical Exploration, volume 17, issue 4, 2014, Pages 231~241
DOI : 10.7582/GGE.2014.17.4.231
Recently, single channel seismic survey for engineering purpose have been used widely taking advantage of simple processing. However it is very difficult to obtain high fidelity subsurface image by single channel seismic due to insufficient fold coverage. Recently, seismic waveform inversion in multi channel seismic survey is utilized for accurate subsurface imaging even in complex terrains. In this paper, we propose the seismic waveform inversion algorithm for velocity model building using a single channel seismic data. We utilize the Gauss-Newton method and assume that subsurface model is 1-Dimensional. Seismic source estimation technique is used and offset effect is also corrected by removing delay time by offset. Proposed algorithm is verified by applying modified Marmousi2 model, and applied to field data set obtained in port of Busan.
New Equivalent Circuit Model for Interpreting Spectral Induced Polarization Anomalous Data
Shin, Seungwook ; Park, Samgyu ; Shin, Dongbok ;
Geophysics and Geophysical Exploration, volume 17, issue 4, 2014, Pages 242~246
DOI : 10.7582/GGE.2014.17.4.242
Spectral induced polarization (SIP) is a useful technique, which uses electrochemical properties, for exploration of metallic sulfide minerals. Equivalent circuit analysis is commonly conducted to calculate IP parameters from SIP data. An equivalent circuit model, which indicates the SIP response of rock, has a non-uniqueness problem. For this reason, it is very important to select the proper model for accurate analysis. Thus, this study focused on suggesting a new model, which suitable for the analysis of an anomalous SIP response, such as ore. A suitability of the new model was verified by comparing it with the existing Dias model and Cole-Cole models. Analysis errors were represented as a normalized root mean square error (NRMSE). The analysis result using the Dias model was the NRMSE of 10.50% and was the NRMSE using the Cole-Cole model of 17.03%. Howerver, because the NRMSE of the new model is 0.87%, it is considered that the new model is more useful for analyzing the anomalous SIP data than other models.
Spectral Induced Polarization Response Charaterization of Pb-Zn Ore Bodies at the Gagok mine
Shin, Seungwook ; Park, Samgyu ; Shin, Dongbok ;
Geophysics and Geophysical Exploration, volume 17, issue 4, 2014, Pages 247~252
DOI : 10.7582/GGE.2014.17.4.247
Gagok Mine, which is skarn deposits, includes sulfide minerals such as sphalerite, galena, chalcopyrite, and pyrrhotite. To explore these minerals, spectral induced polarization (SIP) is relatively effective compared to other geophysical exploration methods because there is a strong IP effect caused by electrode polarization. In the SIP, the chargeability related to sulfide mineral contents and the time constant related to the grain size of the minerals are obtained. For this reason, we aim to compare difference in the mineralized characteristics between two orebodies in the Gagok Mine by using the chargeability and the time constant. For this study, we sampled ores from the south of Wolgok orebody and the north of Sungok orebody. In order to recognize the mineralization characteristics, the metal content of the samples was measured by a potable XRF and the SIP data of the samples were acquired by using a laboratory SIP measurement system. As a result, the metals in the samples such as Pb, Zn, Cu, and Fe were detected by the portable XRF measurement. In particular, the Fe and Zn contents were far higher than the other metals. The Fe and the Zn were caused by the sphalerite and the pyrrhotite through microscopy. The Wolgok orebody had higher sulfide mineral contents than the Sungok orebody and the result corresponded with the chargeability result. However, we considered that the Sungok orebody had a larger sulfide mineral grain size than the Wolgok orebody because the time constant of the Sungok orebody was larger.
Selection of the Optimal Linear Range for the Automated Q-factor Calculation
Kim, Min Young ; Ha, Ji Ho ; Shin, Sung Ryul ; Chung, Woo Keen ;
Geophysics and Geophysical Exploration, volume 17, issue 4, 2014, Pages 253~259
DOI : 10.7582/GGE.2014.17.4.253