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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean earth science society
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Journal DOI :
The Korean Earth Science Society
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Volume & Issues
Volume 32, Issue 7 - Dec 2011
Volume 32, Issue 6 - Oct 2011
Volume 32, Issue 5 - Sep 2011
Volume 32, Issue 4 - Aug 2011
Volume 32, Issue 3 - Jun 2011
Volume 32, Issue 2 - Apr 2011
Volume 32, Issue 1 - Feb 2011
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A Geostatistical Block Simulation Approach for Generating Fine-scale Categorical Thematic Maps from Coarse-scale Fraction Data
Park, No-Wook ; Lee, Ki-Won ;
Journal of the Korean earth science society, volume 32, issue 6, 2011, Pages 525~536
DOI : 10.5467/JKESS.2011.32.6.525
In any applications using various types of spatial data, it is very important to account for the scale differences among available data sets and to change the scale to the target one as well. In this paper, we propose to use a geostatistical downscaling approach based on vaiorgram deconvloution and block simulation to generate fine-scale categorical thematic maps from coarse-scale fraction data. First, an iterative variogram deconvolution method is applied to estimate a point-support variogram model from a block-support variogram model. Then, both a direct sequential simulation based on area-to-point kriging and the estimated point-support variogram are applied to produce alternative fine-scale fraction realizations. Finally, a maximum a posteriori decision rule is applied to generate the fine-scale categorical thematic maps. These analytical steps are illustrated through a case study of land-cover mapping only using the block fraction data of thematic classes without point data. Alternative fine-scale fraction maps by the downscaling method presented in this study reproduce the coarse-scale block fraction values. The final fine-scale land-cover realizations can reflect overall spatial patterns of the reference land-cover map, thus providing reasonable inputs for the impact assessment in change of support problems.
Resistivity Imaging Using Borehole Electrical Resistivity Tomography: A Case of Land Subsidence in Karst Area Due to the Excessive Groundwater Withdrawal
Song, Sung-Ho ; Lee, Gyu-Sang ; Um, Jae-Youn ; Suh, Jung-Jin ;
Journal of the Korean earth science society, volume 32, issue 6, 2011, Pages 537~547
DOI : 10.5467/JKESS.2011.32.6.537
Electrical resistivity tomography surveys using boreholes were applied to reveal the cause of a catastrophic land subsidence accompanied by the excessive groundwater withdrawal in urban karst area and to map the connectivity of disseminated cavities over the study area. In order to understand the hydrogeological characteristics, resistivity using exsitu core samples, groundwater level for five boreholes, and hydraulic conductivity using slug test were measured. The hydraulic conductivity variation ranging from 0.8 to
for five boreholes and a gentle slope of groundwater level indicated that there is no significant characteristics of hydraulic heterogeneity. Core samples of the lime-silicated rock were classified as three groups including cracked, weathered, and fresh and measured the resistivity values ranged from 103 to 161, 218 to 277, and 597 to 662 ohm-m, respectively. Drilling results that showed the cavity filled with clay materials and tomogram for this region indicated resistivity value lower than 50 ohm-m. From the inverted resistivity results for each section with five boreholes, cavity and fractured layer were distributed along the depth between 10 and 20 m overall area and cavities ranging from 4 to 6 m filled with clay materials.
3-D Geological Structure Interpretation by the Integrated Analysis of Magnetotelluric and Gravity Model at Hwasan Caldera
Park, Gye-Soon ; Lee, Chun-Ki ; Yang, Jun-Mo ; Lee, Heui-Soon ; Kwon, Byung-Doo ;
Journal of the Korean earth science society, volume 32, issue 6, 2011, Pages 548~559
DOI : 10.5467/JKESS.2011.32.6.548
3-D Multi-geophysical surveys were carried out around the Hwasan caldera at the Euisung Sub-basin. To overcome the limitations of resolutions in previous studies, dense gravity data and magnetotelluric (MT) data were obtained and analyzed. In this study, the independent inversion models from gravity and MT data were integrated using correlation and classification approaches for 3-D imaging of the geologic structures. A Structure Index (SI) method was proposed and applied to the integration and classification analyses. This method consists of Type Angle (TA) and Type Intensity (TI) values, which are estimated by the spatial correlation and abnormality of the physical properties. The SI method allowed the classification analysis to be effectively performed. Major findings are as follows: 1) pyroclastic rocks around the central area of the Hwasan caldera with lower density and resistivity than those of neighboring regions extended to a depth of around 1 km, 2) intrusive igneous rocks with high resistivity and density were imaged around the ring fault boundary, and 3) a basement structure with low resistivity and high density, at a depth of 3-5 km, was inferred by the SI analysis.
The Applicability for Earth Surface Monitoring Based on 3D Wavelet Transform Using the Multi-temporal Satellite Imagery
Yoo, Hee-Young ; Lee, Ki-Won ;
Journal of the Korean earth science society, volume 32, issue 6, 2011, Pages 560~574
DOI : 10.5467/JKESS.2011.32.6.560
Satellite images that have been obtained periodically and continuously are very effective data to monitor the changes of Earth's surface. Traditionally, the studies on change detection using satellite images have mainly focused on comparison between two results after analyzing two images respectively. However, the interests in researches to catch smooth trends and short duration events from continual multi-temporal images have been increased recently. In this study, we introduce and test an approach based on 3D wavelet transform to analyze the multi-temporal satellite images. 3D wavelet transform can reduce the dimensions of data conserving main trends. Also, it is possible to extract important patterns and to analyze spatial and temporal relations with neighboring pixels using 3D wavelet transform. As a result, 3D wavelet transform is useful to capture the long term trends and short-term events rapidly. In addition, we can expect to get new information through sub-bands of 3D wavelet transform which provide different information by decomposed direction.
The Effect of Wavelet Pair Choice in the Compression of the Satellite Images
Jin, Hong-Sung ; Han, Dong-Yeob ;
Journal of the Korean earth science society, volume 32, issue 6, 2011, Pages 575~585
DOI : 10.5467/JKESS.2011.32.6.575
The effect of wavelet pair choice in the compression of the satellite images is studied. There is a trade-off between compression rate and perception quality. The encoding ratio is used to express the compression rate, and Peak Signal-to-Noise Ratio (PSNR) is also used for the perceptional performance. The PSNR and the encoding ratio are not matched well for the images with various wavelet pairs, but the tendency is remarkable. It is hard to find the pattern of PSNR for sampled images. On the other hand, there is a pattern of the variation range of the encoding ratio for each image. The satellite images have larger values of the encoding ratio than those of nature images (close range images). Depending on the wavelet pairs, the PSNR and the encoding ratio vary as much as 13.2 to 21.6% and 16.8 to 45.5%, respectively for each image. For Synthetic Aperture Radar (SAR) images the encoding ratio varies from 16 to 20% while for the nature images it varies more than 40% depending on the choice of wavelet pairs. The choice of wavelet for the compression affects the nature images more than the satellite images. With the indices such as the PSNR and the encoding ratio, the satellite images are less sensitive to the choice of wavelet pairs. A new index, energy concentration ratio (ECR) is proposed to investigate the effect of wavelet choice on the satellite image compression. It also shows that the satellite images are less sensitive than the nature images. Nevertheless, the effect of wavelet choice on the satellite image compression varies at least 10% for all three kinds of indices. However, the important of choice of wavelet pairs cannot be ignored.
Data Reductions of Gravity Recovery and Climate Experiment (GRACE) Gravity Solutions and Their Applications
Seo, Ki-Weon ;
Journal of the Korean earth science society, volume 32, issue 6, 2011, Pages 586~594
DOI : 10.5467/JKESS.2011.32.6.586
Gravity Recovery and Climate Experiment (GRACE), launched in April, 2002, makes it possible to monitor Earth's mass redistribution with its time-varying gravity observation. GRACE provides monthly gravity solutions as coefficients of spherical harmonics, and thus ones need to convert the gravity spectrum to gravity grids (or mass grids) via the spherical harmonics. GRACE gravity solutions, however, include spatial alias error as well as noise, which requires to suppress in order to enhance signal to noise ratio. In this study, we present the GRACE data processing procedures and introduce some applications of time-varying gravity, which are studies of terrestrial water storage changes, Antarctic and Greenland ice melting, and sea level rise. Satellite missions such as GRACE will continue up to early 2020, and they are expected to be an essential resource to understand the global climate changes.
Detection of a Magnetic Dipole by Means of Magnetic Gradient Tensor
Rim, Hyoung-Rea ;
Journal of the Korean earth science society, volume 32, issue 6, 2011, Pages 595~601
DOI : 10.5467/JKESS.2011.32.6.595
In this paper, I propose the algorithm that the location of a magnetic dipole can be detected from the magnetic gradient tensor. I induce the location vector of a vertically magnetizated dipole from the magnetic gradient tensor. Deficit of magnetic moment of magnetic dipole makes the induced location information incomplete. However, if the observation of magnetic gradient tensor would be collected on more points, the algorithm is able to catch the location of the magnetic dipole by clustering the solution of the proposed algorithm. For example, I show that the synthetic case of borehole observation of magnetic gradient tensor can find the source location successively by picking common solution area.
Two-dimensional Inversion of Sea-effect-corrected Magnetotelluric (MT) Data in Jeju Island
Yang, Jun-Mo ; Lee, Heui-Soon ; Lee, Choon-Ki ; Park, Gye-Soon ;
Journal of the Korean earth science society, volume 32, issue 6, 2011, Pages 602~612
DOI : 10.5467/JKESS.2011.32.6.602
Jeju Island, a volcanic island located in South Korea, has been one of the main targets of geophysical and/or geological studies because of its tectonic importance related to the volcanism and tectonic link to the southern part of the Korean Peninsula. Recently, as a number of broad-band magnetotelluric (MT) measurements were made, we have examined the deep part of the island. In such an insular setting, it is not easy to properly recover the deep structures such as the lower crust and the upper crust using MT data, because their low-frequency components are strongly affected by the surrounding sea of the island. In this study, we apply the sea-effect correction to the existing MT data collected at a total of 102 sites in Jeju Island. The sea-effect correction makes remarkable changes in the observed MT data at frequencies below 1 Hz, clearly indicating the existence of a conductive lower crust. The 2-D inversion results for both Jeju Southern Line (JSL) and Jeju Northern Line (JNL) show that the transition zone separating the resistive upper crust and conductive lower crust exists at a depth of 20 km on average.
Restoration, Prediction and Noise Analysis of Geomagnetic Time-series Data
Ji, Yoon-Soo ; Oh, Seok-Hoon ; Suh, Baek-Soo ; Lee, Duk-Kee ;
Journal of the Korean earth science society, volume 32, issue 6, 2011, Pages 613~628
DOI : 10.5467/JKESS.2011.32.6.613
Restoration, prediction and noise analysis of geomagnetic data measured in the Korean Peninsula were performed. Restoration methods based on an optimized principal component analysis (PCA) and the geostatistical kriging approach were proposed, and its effectiveness was also interpreted. The PCA-based method seemed to be effective to restore the periodical signals and the geostatistical approach was stable to fill the gaps of measurements. To analyze the noise level for each observatory, the geomagnetic time-series was plotted by scattergram which reflects the spatial variation, using data observed during same period. The scattergram showed that the observation made at Cheongyang seemed to have better quality in spatial continuity and stability, and the restoration result was also better than that of Icheon site. For the restoration, both of the methods, geostatistical and optimizaed PCA, showed stable result when the missing of observation was within 20 points. However, in case of more missing observations than 20 points and prediction problem, the optimized PCA seemed to be closer to the real observation considering the frequency-domain characteristics. The prediction using the optimized PCA seems to be plausible for one day of period for interpretation.
A New Structural Model for Predicting Effective Thermal Conductivity of Variably Saturated Porous Materials
Cha, Jang-Hwan ; Koo, Min-Ho ; Keehm, Young-Seuk ;
Journal of the Korean earth science society, volume 32, issue 6, 2011, Pages 629~639
DOI : 10.5467/JKESS.2011.32.6.629
Based on Maxwell-Eucken(ME) model, which is one of structural models, a new model for predicting the effective thermal conductivity of variably saturated porous materials is proposed. The new model is a linear combination of three ME models having matrix, water, and air as a continuous phase. The coefficient of the corresponding linear equation is defined by a parameter referred to as 'the continuity coefficient', which provides a relative degree of continuity of each phase. The continuity coefficient of matrix is assumed to be linearly proportional to porosity. The model can be linear or nonlinear depending on how the continuity coefficients of water and air vary with water saturation. The feasibility of the proposed model was examined by both numerical and experimental results. Both linear and nonlinear models showed a high accuracy of prediction with
values of 0.86-0.98 and 0.88-0.99, respectively. The numerical and experimental results also showed that the continuity coefficient of matrix was linearly proportional to porosity. Therefore, the proposed prediction model can be effectively used to estimate effective thermal conductivity of unsaturated porous materials by measuring porosity, water content and mineralogical compositions of matrix.
Earthquake Wave Propagation Using Staggered-grid Finite-difference Method in the Model of the Antarctic Region
Oh, Ju-Won ; Min, Dong-Joo ; Lee, Ho-Yong ; Park, Min-Kyu ;
Journal of the Korean earth science society, volume 32, issue 6, 2011, Pages 640~653
DOI : 10.5467/JKESS.2011.32.6.640
We simulate the propagation of earthquake waves in the continental margin of Antarctica using the elastic wave modeling algorithm, which is modified to be suitable for acoustic-elastic coupled media and earthquake source. To simulate the various types of earthquake source, the staggered-grid finite-difference method, which is composed of velocity-stress formulae, can be more appropriate to use than the conventional, displacement-based, finite-difference method. We simulate the elastic wave propagation generated by earthquakes combining 3D staggered-grid finite-difference algorithm composed of displacement-velocity-stress formulae with double couple mechanisms for earthquake source. Through numerical tests for left-lateral strike-slip fault, normal fault and reverse fault, we could confirm that the first arrival of P waves at the surface is in a good agreement with the theoretically-predicted results based on the focal mechanism of an earthquake. Numerical results for a model made after the subduction zone in the continental margin of Antarctica showed that earthquake waves, generated by the reverse fault and propagating through the continental crust, the oceanic crust and the ocean, are accurately described.
Inversion Analysis of Magnetotelluric Data Acquired in Geothermal Area of Seokmo Island
Lee, Seong-Kon ; Park, In-Hwa ; Chung, Yong-Hyun ; Lee, Tae-Jong ;
Journal of the Korean earth science society, volume 32, issue 6, 2011, Pages 654~664
DOI : 10.5467/JKESS.2011.32.6.654
A field campaign of magnetotelluric (MT) and audio-frequency MT (AMT) survey was done at 36 measurement points as a complementary for the previous 44 MT measurements completed during the period of 2005-2006. The purpose of additional MT survey is to investigate the possible fracture system in Seokmo Island, which is conceived to be crucial in accumulation and migration of geothermal hot spring in this area. We have done 2D and 3D inversions of overall MT and AMT data distributed on a grid to interpret subsurface of extended area. The inversion results reveal that at least two major faults are imaged in the inversion results, one of which is in NNE-SWW with steep dip, and another is in E-W direction.
Generation of Pseudo Porosity Logs from Seismic Data Using a Polynomial Neural Network Method
Choi, Jae-Won ; Byun, Joong-Moo ; Seol, Soon-Jee ;
Journal of the Korean earth science society, volume 32, issue 6, 2011, Pages 665~673
DOI : 10.5467/JKESS.2011.32.6.665
In order to estimate the hydrocarbon reserves, the porosity of the reservoir must be determined. The porosity of the area without a well is generally calculated by extrapolating the porosity logs measured at wells. However, if not only well logs but also seismic data exist on the same site, the more accurate pseudo porosity log can be obtained through artificial neural network technique by extracting the relations between the seismic data and well logs at the site. In this study, we have developed a module which creates pseudo porosity logs by using the polynomial neural network method. In order to obtain more accurate pseudo porosity logs, we selected the seismic attributes which have high correlation values in the correlation analysis between the seismic attributes and the porosity logs. Through the training procedure between selected seismic attributes and well logs, our module produces the correlation weights which can be used to generate the pseudo porosity log in the well free area. To verify the reliability and the applicability of the developed module, we have applied the module to the field data acquired from F3 Block in the North Sea and compared the results to those from the probabilistic neural network method in a commercial program. We could confirm the reliability of our module because both results showed similar trend. Moreover, since the pseudo porosity logs from polynomial neural network method are closer to the true porosity logs at the wells than those from probabilistic method, we concluded that the polynomial neural network method is effective for the data sets with insufficient wells such as F3 Block in the North Sea.
A Comparison Study on Near-surface High-resolution Seismic Data by Different Source and Geophone Types
Kim, Hyoung-Soo ; Keehm, Young-Seuk ;
Journal of the Korean earth science society, volume 32, issue 6, 2011, Pages 674~686
DOI : 10.5467/JKESS.2011.32.6.674
Choosing a seismic source and geophone type including a coupling method can be the most important factor in shallow seismic surveys. We studied the characteristics of seismic signals by analyzing 6 different seismic data sets that collected from several sources and geophone conditions. Geophones attached to weight plate (1.8 kg) can be easily and economically installed on the paved road where geophones with spikes would cause the coupling problem. In addition, experiments in this study revealed that a small handy hammer can be used as a seismic source by striking the paved road to generate the seismic signals within 200 ms two-way travel time. Attaching weight plates to geophones may change the geophone response curve which generally depends on the geophone mass, but the change seems not to give significant differences in the first arrival of refracted wave and in the pattern of reflection events. Consequently, using weight plates on paved roads can be an efficient and cost-saving method in the near-surface high-resolution seismic surveys.
Analysis of Highschool Students' Misconception Textbooks Related to the Declination
Lee, Gyu-Ho ;
Journal of the Korean earth science society, volume 32, issue 6, 2011, Pages 687~703
DOI : 10.5467/JKESS.2011.32.6.687
The declination is an important concept because it is the underlying concept to understand the plate tectonics and also is used to decide one's location by using the compass and the map in real life. So this study surveys the description of declination being used in six of the seventh curriculum earth science II textbooks followed by the investigation of the possible of misconceptions that the highschool students might have. Utilizing an inventory of key concept, this study examines the actual misconceptions of highschool students, and investigates the relationship between misconceptions and textbooks. As a result, highschool students possess some misconceptions particularly with respect to the magnetic north pole which is caused by a lack of explanation about declination and by a wrong illustration. Therefore we suggest that detailed explanations of declination with non-dipole effect and precise illustrations be provided in the textbook for students th have a better understanding about declination.