• Title/Summary/Keyword: Geophysical property

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Integration of Geophysical Properties and Geospatial Information for Telecommunication Modeling

  • Kim, Jeong-Woo;Lee, Dong-Cheon;Pack, Jeong-Ki;Yom, Jae-Hong;Kwon, Jay-Hyon;Jeong, Nam-Ho
    • Proceedings of the KSRS Conference
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    • 2002.10a
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    • pp.745-745
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    • 2002
  • Both geophysical and geospatial data provide important information in the establishment of the optimal telecommunication systems especially in the mobile telecommunication environment. The objective of this study is to utilize geophysical properties and geospatial information in the analysis of the telecommunication environment through point-to-point wave property modeling. Geophysical properties associated with wave propagation parameters of the earth surface were analyzed based on hierarchical land classification using Landsat ETM+ and IKONOS images. Three-dimensional geospatial information was obtained by processing stereo aerial images. The results show that the accurate geospatial information and reliable geosphysical property of the surface improve the prediction of receiving power of the receivers located near corners of the buildings where diffractions occur. The wave property model developed from accurate telecommunication environment could be applied to optimal cell planning and delay time analysis.

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Comparison of Physical Properties obtained from Geophysical Well Log and Core Property Measurements in Gabsan Formation (갑산층 석회암지역에서의 코어물성과 검층물성 비교)

  • 김영화;김기주
    • The Journal of Engineering Geology
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    • v.9 no.3
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    • pp.253-265
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    • 1999
  • Physical properties of Paleozoic sedimentary rocks in Gabsan formation in Jechon area were obtained by both geophysical well log methods and core property measurements, and the similarity and difference shown between the well log and core log responses were analyzed. The physical properties obtained are natural gamma, resistivity and density. From the difference in density response between the well log and core measurement, the need of correction for natural gamma effect on density log was strongly suggested. And fairly good correlation was obtained between well log and core properties, and among natural gamma, resistivity and density by applying natural gamma correction on density log. It is noted that shale in Gabsan formation reveals very high density, even higher than the density of adjacent non-porous limestone.

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A Study on the Errors in Depth from a Geophysical Logging Well (물리검층공에서의 심도오차에 대한 분석과 보정)

  • 김영화;장승익
    • The Journal of Engineering Geology
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    • v.8 no.1
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    • pp.87-98
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    • 1998
  • Multiple logging techniques consisting of geophysical logs, care logs, physical property measurements on core samples have been adopted on a test borehole drilled in the Pungam basin ; a small Cretaceous sedimentary basin located in Sosok area, Hongchon-gun, Kangwon Province, Korea. This study has been made to solve the problem of mismatches between the results of geophysical log and core log analyses. And the cause and range of depth errors as well as logging responses were studied. The result shows that the depth error caused by geophysical log is so small that it can be used as a reliable depth criterion in the borehole. The analysis of physical property measurements is also shown as very effective in determining the real depth and the geology of the borehole.

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Lithology Determination by Log Analysis from a Borehole-PABH1 in the Pungam Sedimentary Basin (풍암퇴적분지 내 시추공 PABH1에서의 물리검층에 의한 암상의 판정)

  • 김영화;장승익
    • The Journal of Engineering Geology
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    • v.8 no.2
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    • pp.163-173
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    • 1998
  • Suite of log analysis techniques consisting of geophysical well log, geological core log, and physical core log have been made to understand the well log responses and to determine the lithology of a test borehole-PABH1 located in Pungam sedimentary basin, Sosok, Hongchon-gun, Kangwon Province. Geological core logging has been precisely made over the cores taken between 64 and 124 meters, and 11 groups of rock types were deduced. Using the core samples divided by 11 groups, geophysical property measurements consisting of resistivity, natural gamma and density were made. Each rock group in the area is shown to have its characteristic physical response from geophysical well log and geophysical core logs. The outstanding physical responses particularly shown from siltstone, coarse sandstone to conglomerate, and granitic gneiss in the area were effectively used as keybeds in correlating the geophysical well logs to the result of geological core logs.

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Proposed Survey Steps for Investigation of Land-Creeping Susceptibility Areas: A Focus on Geophysical Mapping of the Yongheung-dong, Pohang, Korea

  • Kim, Jeong-In;Lee, Sun-Joong;Kim, Kwan-Soo;Lee, Jae-Eun;Sa, Jin-Hyun;Kim, Ji-Soo
    • The Journal of Engineering Geology
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    • v.31 no.3
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    • pp.269-281
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    • 2021
  • Land creeping is the imperceptibly slow, steady, downward movement o f slope-forming soil or rock. Because creep-related failures occur frequently on a large scale without notice, they can be hazardous to both property and human life. Korea Forest Service has operated the prevention and response system from land creeping which has been on the rise since 2018. We categorized and proposed three survey steps (e.g., preliminary, regional, detailed) for investigation of creeping susceptibility site with a focus on geophysical mapping of a selected test site, Yongheung-dong, Pohang, Korea. The combination of geophysical (dipole-dipole electrical resistivity tomography and reciprocal seismic refraction technique, well-logging), geotechnical studies (standard penetrating test, laboratory tests), field mapping (tension cracks, uplift, fault), and comprehensive interpretation of their results provided the reliable information of the subsurface structures including the failure surface. To further investigate the subsurface structure including the sliding zone, we performed high-resolution geophysical mapping in addition to the regional survey. High-resolution seismic velocity structures are employed for stability analysis because they provided more simplified layers of weathering rock, soft rock, and hard rock. Curved slip plane of the land creeping is effectively delineated with a shape of downslope sliding and upward pushing at the apex of high resistive bedrock in high-resolution electrical resistivity model with clay-mineral contents taken into account. Proposed survey steps and comprehensive interpretation schemes of the results from geological, geophysical, and geotechnical data should be effective for data sets collected in a similar environment to land-creeping susceptibility area.

Prediction of Discontinuity and Determination of Rock Property ahead of Tunnel Face by VSP application (수직 탄성파탐사를 응용한 터널 전방의 불연속면 예측과 암반 물성 파악)

  • 남기천;이진무;차성수
    • Tunnel and Underground Space
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    • v.5 no.3
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    • pp.214-222
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    • 1995
  • Geological events which are undetected by the surface geophysical or geological survey phase can cause many problems, especially when the tunnel is excavated by TBM. To detect the geological events ahead of tunnel face, a seismic method applied from VSP method is used. Generally uniaxial geophone has been used in surface seismic survey. But this time, triaxial geophone is used to reduce the noise of tunnel wave. DME(Dip moveout Enhancement) filter and diffraction stack method are used. Applying these techniques to the road tunnel in construction, it is proved that the geological events ahead of tunnel face is fairly well predicted. From the seismic trace, Vp and Vs which are related to the rock property can be also obtained. Rock property and proper support design can be dedced from these parameters.

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Geostatistical inversion of geophysical data for estimation of rock quality (물리탐사 자료의 지구통계학적 역산에 의한 암반강도 추정)

  • Oh, Seok-Hoon;Suh, Baek-Soo
    • 한국지구물리탐사학회:학술대회논문집
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    • 2008.10a
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    • pp.63-67
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    • 2008
  • Geostatistical inverse approach using geophysical data was applied to indirectly make the RMR classification at points apart from boreholes. The geostatistical appoach was usually used to find optimized estimation which supports two or more different physical properties at unsampled points. However, in this study, an approach to solve inverse problem was proposed. The primary variable, RMR values obtained at known boreholes, is geostatistically simulated with many realization at pre-defined grid point according to the variogram model. The simulated values are sequentially compared with the physical property resulted from geophysical survey at an arbitrary grid point, and the most similar one is chosen. This process means that the spatial distribution of primary variable, RMR, is conformed well to the original pattern of the borehole observation, and ensure to fit the geophysical survey result to reflect the correlation between different physical properties.

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Joint Inversion of DC Resistivity and Travel Time Tomography Data: Preliminary Results (전기비저항 주시 토모그래피 탐사자료 복합역산 기초 연구)

  • Kim, Jung-Ho;Yi, Myeong-Jong;Cho, Chang-Soo;Suh, Jung-Hee
    • Geophysics and Geophysical Exploration
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    • v.10 no.4
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    • pp.314-321
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    • 2007
  • Recently, multi-dimensional joint inversion of geophysical data based on fundamentally different physical properties is being actively studied. Joint inversion can provide a way to obtaining much more accurate image of the subsurface structure. Through the joint inversion, furthermore, it is possible to directly estimate non-geophysical material properties from geophysical measurements. In this study, we developed a new algorithm for jointly inverting dc resistivity and seismic traveltime data based on the multiple constraints: (1) structural similarity based on cross-gradient, (2) correlation between two different material properties, and (3) a priori information on the material property distribution. Through the numerical experiments of surface dc resistivity and seismic refraction surveys, the performance of the proposed algorithm was demonstrated and the effects of different regularizations were analyzed. In particular, we showed that the hidden layer problem in the seismic refraction method due to an inter-bedded low velocity layer can be solved by the joint inversion when appropriate constraints are applied.

Geotechnical properties of gas hydrate bearing sediments (가스 하이드레이트 부존 퇴적토의 지반공학적 물성)

  • Kim, Hak-Sung;Cho, Gye-Chun;Lee, Joo-Young
    • 한국신재생에너지학회:학술대회논문집
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    • 2011.05a
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    • pp.151-151
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    • 2011
  • Large amounts of natural gas, mainly methane, in the form of hydrates are stored on continental margins. When gas hydrates are dissociated by any environmental trigger, generation of excess pore pressure due to released free gas may cause sediment deformation and weakening. Hence, damage on offshore structures or submarine landslide can occur by gas hydrate dissociation. Therefore, geotechnical stability of gas hydrate bearing sediments is in need to be securely assessed. However, geotechnical characteristics of gas hydrates bearing sediments including small-strain elastic moduli have been poorly identified. Synthesizing gas hydrate in natural seabed sediment specimen, which is mainly composed of silty-to-clayey soils, has been hardly attempted due to their low permeability. Moreover, it has been known that hydrate loci in pore spaces and heterogeneity of hydrate growth in specimen scale play a critical role in determining physical properties of hydrate bearing sediments. In the presented study, we synthesized gas hydrate containing sediments in an instrumented oedometric cell. Geotechnical and geophysical properties of gas hydrate bearing sediments including compressibility, small-strain elastic moduli, elastic wave, and electrical resistivity are determined by wave-based techniques during loading and unloading processes. Significant changes in volume change, elastic wave, and electrical resistivity have been observed during formation and dissociation of gas hydrate. Experimental results and analyses reveal that geotechnical properties of gas hydrates bearing sediments are highly governed by hydrate saturation, effective stress, void ratio, and soil types as well as morphological feature of hydrate formation in sediments.

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