• Economic and Environmental Geology
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• v.35 no.2
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• pp.155-162
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• 2002

There are many typical epithermal deposits scattering in the Taran of central Kalimantan. Indonesia. To get the shallow geological information, we carried out the geophysical exploration: spontaneous potential survey, in-suite magnetic susceptibility measurement and relistivity survey method in this area for a few weeks from September 30th to October 27th in 1997. SP survey (Fluke 27 multimeter)/magnetic susceptibility (EK -7 meter) measurement was carried out with a 250m$\times$10m lattice net in N45$^{\circ}$W direction. The dipole-dipole array resistivity survey was conducted with an electrode spacing of ${\alpha}$=30 m and electrode separation index n=7 at the line 5. The result shows that was the gold bearing quartz vein area can be divided into two type lone: low sulfidation type and high sulfidation type zone. The low resistivity value in the survey line 5 indicated a fracture Bone associated with the high sulfidation zone.

• Journal of the Korean Geophysical Society
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• v.3 no.2
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• pp.113-126
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• 2000

We have conducted multiple geophysical surveys to investigate the geoenvironmental change of the Nanjido Landfill due to the stabilization process. Geophyscial surveys are comprized of gravity, magnetic, dipole-dipole electrical and SP methods. Due to the field conditions, surveys were conducted on the top surface of the landfill no.2 and southern border areas in front of landfills. The gravity anomalies obtained on the top surface of the landfill no.2 in 1999 show that the gradient of the anomaly on the central area is decreasing in comparison with that observed four years ago. The complexity of magnetic anomaly pattern it also decreasing. These facts suggest that the stabilization work of the Nanjido landfill makes some progress by compaction process due to repetitive subsidence and refilling. The dipole-dipole electrical resistivity and SP data obtained on the outside of the waterproof wall at the landfill no.1 were severely affected by unsatisfactory surface conditions. On the other hand, the dipole-dipole electrical resistivity profiles obtained on the inside and outside parts of the waterproof wall at the landfill no.2 show the blocking effect of leachate flow by the waterproof wall. Few SP anomalies are observed on the top and side surfaces of the landfill no.2, but SP anomalies obtained on the base area inside the waterproof wall strongly reflect the effect of leachate collecting wells.

• Journal of the Korean Geophysical Society
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• v.4 no.2
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• pp.103-111
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• 2001

Geophysical survey was carried out to derive some information on the existence of near-surface anomalous body at Reung-Chi area in Kongju. Resistivity, seismic, magnetic and gravity method were applied. Geophysical survey that was applied was the electrical resistivity survey, seismic survey, magnetic survey, gravity survey. These surveys are analyzed to provide data of high resolution. As a result of analysis of resistivity survey, anomalies showing high resistivity anomaly than around appeared, and the one showing M-shape out of those explains the possibility that underground common or other underground structure or geographical anomalous zone could exist in the underground. As a result of analysis of seismic survey, it is clear that the low velocity layer is spread as far as the bottom of the underground. It is possible to presume that it is a phenomenon appearing while going through the underground space where it is lying in the underground. Area that shows unusual situation in interpretation of data on seismic waves are included into the area that once showed resistivity anomaly, the results of both seismic surveys come in accord. As a result of magnetic survey, a circle-shape of twin magnetic fields in the area where abnormalities are shown between electrical resistivity survey and seismic survey is appeared. Given the area of gravity survey, abnormalities whose density is different from the one around the bottom of the underground. As a result of analogizing the data of underground of the subsurface based on analysis of data from each survey, it was interpreted that anomalous zone exists commonly in the research areas.

• Geophysics and Geophysical Exploration
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• v.25 no.1
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• pp.26-37
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• 2022

Recently, multiple methods using small aircraft for geophysical exploration have been suggested as a result of the development of information and communication technology. In this study, we introduce the hybrid unmanned aircraft electromagnetic system of the Korea Institute of Geosciences and Mineral resources, which is under development. Additionally, data processing and interpretation methods are suggested via the analysis of datasets obtained using the system under development to verify the system. Because the system uses a three-component receiver hanging from a drone, the effects of rotation on the obtained data are significant and were therefore corrected using a rotation matrix. During the survey, the heights of the source and the receiver and their offsets vary in real time and the measured data are contaminated with noise. The noise makes it difficult to interpret the data using the conventional method. Therefore, we developed a recurrent neural network (RNN) model to enable rapid predictions of the apparent resistivity using magnetic field data. Field data noise is included in the training datasets of the RNN model to improve its performance on noise-contaminated field data. Compared with the results of the electrical resistivity survey, the trained RNN model predicted similar apparent resistivities for the test field dataset.

• Geophysics and Geophysical Exploration
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• v.6 no.2
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• pp.87-94
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• 2003

ULF geomagnetic field anomalies related to earthquakes have been reported and a mechnism that magnetic field variations could be generated by the induced telluric current due to the high frequency fluctuation of conductivity in a fault Bone have been proposed. In this study, we calculated electromagnetic anomalies using a simple fault model and investigated the possibility of significant perturbation. Since low frequency electromagnetic fields are modulated by the high frequency oscillation of conductivity and the modulated fields are concentrated in a narrow ULF band, the electromagnetic fields in ULF band could be perturbed significantly. The amplitude of electromagnetic field anomaly depends on various factors: the geometry and conductivity of fault zone, the magnitude and frequency of conductivity fluctuation, the resistivity structure of crust or mantle, the frequency bandwidth of observational data and so on. Therefore, it is strongly required to reveal the deep resistivity structure of crust a.: well ah the structure of fault zone and to ,select the optimal observation frequency band for the observation of electromagnetic activities related with earthquakes.

• Journal of the Korean earth science society
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• v.21 no.4
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• pp.408-422
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• 2000

Multiple geophysical methods were applied over the Manjang cave area in Cheju Island to compare and contrast the effectiveness of each method for exploration of underground cavities. The used methods are gravity, magnetic, electrical resistivity and GPR(Ground Pentrating Radar) survey, of which instruments are portable and operations are relatively economical. We have chosen seven survey lines and applied appropriate multiple surveys depending on the field conditions. In the case of magnetic method. two-dimensional grid-type surveys were carried out to cover the survey area. The geophysical survey results reveal the characteristic responses of each method relatively well. Among the applied methods, the electric resistivity methods appeared to be the most effective ones in detecting the Manjang Cave and surrounding miscellaneous cavities. Especially, on the inverted resistivity section obtained from the dipole-dipole array data, the two-dimensional distribution of high resistivity cavities are revealed well. The gravity and magnetic data are contaminated easily by various noises and do not show the definitive responses enough to locate and delineate the Manjang cave. But they provide useful information in verifying the dipole-dipole resistivity survey results. The grid-type 2-D magnetic survey data show the trend of cave development well, and it may be used as a reconnaissance regional survey for determining survey lines for further detailed explorations. The GPR data show very sensitive response to the various shallow volcanic structures such as thin spaces between lava flows and small cavities, so we cannot identify the response of the main cave. Although each geophysical method provides its own useful information, the integrated interpretation of multiple survey data is most effective for investigation of the underground caves.

• 한국지구물리탐사학회:학술대회논문집
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• 2000.09a
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• pp.112-131
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• 2000

In spite of its many strong points, pole-pole electrode configuration is not often used for ground electrical resistivity survey except for bore hole survey as normal logging and for archaeological investigation. Above all, poor spatial resolution of pole-pole survey may be responsible for this. But recent experiences so far gained by the present authers lead them to think that pole-pole survey can be at least a viable means of reconnaissance survey in near-surface conductive environment and an effective interpretational scheme may augment its resolution. As well known, a response of any other electrode configuration is a linear combination of pole-pole responses. Based on this principle of linear superposition and the principle of reciprocity, the other 'responses' can be derived with simple additions and subtractions of pole-pole responses. Though such responses are not always correct due to the adverse effects of noises, combined with the potential decay curves, they can be helpful to interprete better pole-pole survey data especially in connection of the resolution. This can be comparable to the use of the first or second derivatives of gravity and magnetic intensity surveys.

• 한국지구물리탐사학회:학술대회논문집
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• 2001.09a
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• pp.122-140
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• 2001

We have applied the geophysical survey, mainly electric and electromagnetic (EM) methods, to a test site contaminated by hydrocarbon waste disposal and local spill. The multi-frequency, moving source & receiver EM survey along with ground penetrating radar (GPR) showed a fairly good performance in detection of buried metal pipes and objects. Magnetic survey measuring vertical and horizontal gradients were so sensitive to the small metallic objects spread over the surface that it's hard to discriminate the buried pipe. We chose electrical resistivity, EM and GPR survey to examine the soil contamination. Depth slices of resistivity distribution as the results of the inversion of resistivity and EM data coincided each other and closely matched the contaminated area determined by chemical analysis of the soil samples. GPR images did not show the reflection events related with contamination plume since there are no distinct spill in this site. We inferred the contamination using the penetration depth of the GPR energy, which could be used as auxiliary information to the resistivity and EM results. We summarized the applicability of each survey methods based on this results and proposed a desirable survey scheme for the determination of hydrocarbon contaminated site.

• Progress in Superconductivity and Cryogenics
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• v.25 no.2
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• pp.10-13
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• 2023

High-T_C superconductivity (HTSC) has been the central issue in the field of condensed matter physics for decades. An essential part of the research on superconductivity is finding new exotic superconductors. It was recently suggested that Ir-substituted La_0.7Sr_0.3MnO₃ (LSMIO) is a new high-T_C superconductor. However, systematic studies to experimentally verify the superconductivity have not been done. Here, we report the growth processes of LSMIO thin films and their electrical transport properties. We observed a clear negative correlation between the intensity of the laser utilized for film deposition and the Curie temperature of the deposited film. We attributed this effect to the suppression of Sr concentration in the LSMIO films as the laser intensity increased. However, our LSMIO films show conventional ferromagnetism instead of HTSC. To realize the HTSC in LSMIO systems, further exploration of diverse compositions of LSMIO compounds is essential.