• Journal of the Korean earth science society
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• v.44 no.3
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• pp.210-221
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• 2023

The purpose of this study is to evaluate the content knowledge and problem solving process used by pre-service earth science teachers while discriminating faults on geological maps. For this, we collected and evaluated data on fixation duration and gaze plot, while pre-service earth science teachers (N=12) solved the problem on faults interpretation using an eye tracker (Tobii Pro Glass 2 model). The results were as follows. First, most of the pre-service earth science teachers know the concepts of the normal and reverse fault but they do not know the procedural knowledge essential for fault interpretation on geological maps. Second, the pre-service earth science teachers did not draw a geological cross-sectional map to interpret the fault on the geological map and interpreted the fault based on two-dimensional information collected from the geological map rather than three-dimensional information. Therefore, it is essential to improve the teaching and learning environment so that pre-service earth science teachers who will become earth science teachers in the future can learn procedural knowledge essential to comprehend natural phenomena including understanding natural phenomena. The results of this study can substantially help organize a new earth science curriculum or develop materials on teachers' education in the future.

• Tunnel and Underground Space
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• v.21 no.4
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• pp.251-263
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• 2011

The geomechanical characteristics of rock and the structural geological feature of the fault should be studied and examined for the successful construction of large-span tunnel. In this case study, that is a important case for the tunnel collapse and reinforcement during the construction for the waterway tunnel at large thrust fault zone in schist, we carried out geological and geotechnical survey for make the cause and mechanism of tunnel collapse. Also, we have designed the reinforcement and re-excavation for the safe construction for collapse zone and have carried out successfully the re-excavation and finished the final concrete lining.

• Journal of The Geomorphological Association of Korea
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• v.25 no.1
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• pp.19-30
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• 2018

This study tries to infer fault lines and produce a map for the lines based on a classification of fault-related landforms and fluvial landformsin the Gyeongju area of the Yangsan Fault Valley. Fault activities in the study area are thought to be older than the time of river formation or stronger than the erosion by river, while the northern and southern parts of the study area seem to have experienced fault activities after valley formation. It is also possible that weaker fault activities than the erosion by river seem to have been prevailed in the parts. In the study area, the Gyeongju alluvial fan is located within a wide erosional valley at the joint area of the Yangsan and Ulsan Faults. From the distribution of the landforms, it is inferred that several fault lines parallel to the Yangsan Fault are distributed at both sides of the fault valley. In particular, the area from Bae-dong to Nogok-ri, Naenam-myeon shows the most obvious linearity of the landforms within the study area. Several fault lines with a direction of NNE-SSW are also found around the epicenter of the 2016 Gyeongju Earthquake.

• Journal of the Korean Institute of Landscape Architecture
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• v.43 no.5
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• pp.55-64
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• 2015

In this study, negative air ions, which can increase comfort and positively influence human health, was set as an evaluative factor for school forests. The characteristics, location and microclimate of school forests were examined to determine an effective school forest model for maximum negative air ion generation. It also aimed to provide basic data for the development of urban green fields. The negative air ion concentrations were different according to the green types. The order from the highest to the lowest was: single-layer structure($934ea/cm^3$) > multi-layer structure($794ea/cm^3$) > grass($553ea/cm^3$) > bare ground($529ea/cm^3$). As for the correlation with microclimate, negative air ion concentration was negatively correlated with temperature. The negative air ion concentration was significantly different according to planting type. The negative air ion concentration was higher at single-layer structure sites than at multi-layer structure sites, which appears to indicate that the temperature is higher when the vegetation structure was single-layer compared to multi-layer. Wind speed was higher at the single-layer planted site than at the multi-layer planted site. The vegetation wind shielding effect was lower at single-layer planted sites than at multi-layer planted sites. The single-layer planted site provided more favorable conditions for the generation and dispersion of negative air ions.

• The Journal of the Petrological Society of Korea
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• v.10 no.3
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• pp.148-156
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• 2001

We report $^{230}Th/^{234}U$ disequilibrium ages of fracture-filling carbonate veins from the Ipsil and Janghangri fault zones, Gyeongju, Korea by multiple collector inductively coupled plasma mass spectrometry. The U and Th fraction was extracted from totally dissolved samples by rapid and convenient coprecipitation and ion exchange chemistry. The recovery was around 80% for Th and 70% for U. The $^{234}U/^{238}U,\;^{230}Th/^{232}Th$ ratios were analysed for this preconcentrated fraction and the U/Th ratio was directly analysed for untreated sample solution. The $^{234}U-^{230}Th$ system is in secular equilibrium for the Ipsil carbonate samples, supporting previously reported ESR ages. The detrital-corrected $^{230}Th/^{234}U$ age of the Janghangri carbonate samples is $48\pm$41 ka, which constrains the minimum age of the fracture zone.

• The Journal of Engineering Geology
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• v.28 no.2
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• pp.183-192
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• 2018

It is imperative to inject carbon dioxide($CO_2$) into an aquifer for alleviating the emission of $CO_2$. However, faults in the aquifer can be reactivated due to pressure increasement. Analyses of pressure change of the aquifer is necessary to prevent the fault reactivation. In this research, we assess the stability of an aquifer in Pohang Yeongil bay by investigating the pressure variation of faults EF1 and EF2. Two scenarios, which repeat $CO_2$ injection and suspension during two years, are simulated. Each scenario includes cases of injection rates of 20, 40, and 100 tons/day. In addition, we analyze planned and predicted injection rates for each case. In case of 20 tons/day, the maximum pressure of faults is 65% of the reactivation pressure. Even if daily injection rates are increased to 40 and 100 tons/day, the maximum pressures are 71% and 80% of the reactivation pressures, respectively. For 20 and 40 tons/day cases, planned injection rates almost accord with predicted injection rates during whole simulation period. On the other hand, predicted injection rates are smaller than planned injection rates for the 100 tons/day case due to bottom-hole pressure limit of the injection well.

• The Journal of Engineering Geology
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• v.19 no.4
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• pp.509-515
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• 2009

Three earthquakes with local magnitude ($M_L$) greater than 3.0 occurred on April 24, June 2 and September 12 in 1999 nearby the Gyeongju area. Redetermined epicenters were located within the radius of 1 km. We carried out waveform inversion analysis to estimate focal mechanism of June 2 event, and P and S wave polarity and their amplitude ratio analysis to estimate focal mechanisms of April 24 and September 12 events. June 2 and September 12 events had similar fault plane solutions each other. The fault plane solution of April 24 event included those of other 2 events, but its distribution range was relatively broad. Focal mechanisms of those events had a strike slip faulting with a small normal component. P-axes of those events were ENE-WSW which were similar to previous studies on the P-axis of the Korean Peninsula. Considering distances between epicenters, similarities of seismic waves and sameness of polarities of seismic data recorded at common seismic stations, these events might occurred at the same fault. The seismic moment of June 2 event was estimated to be $3.9\;{\times}\;10^{14}\;N{\cdot}m$ and this value corresponded to the moment magnitude ($M_W$) 3.7. The moment magnitude estimated by spectral analysis was 3.8, which was similar to that estimated by waveform inversion analysis. The average stress drop was estimated to be 7.5 MPa. Moment magnitudes of April 24 and September 12 events were estimated to be 3.2 and 3.4 by comparing the spectrum of those events recorded at common single seismic station.

• Economic and Environmental Geology
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• v.55 no.6
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• pp.633-648
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• 2022

Gravity data were analyzed to identify the cause of clustered seismicity that occurred intensively in Yeoncheon, located in the central part of the Korean Peninsula. Our analysis suggests that the En echelon faults developed in the northwest-southeast direction. In addition, in the eastern part of the Dongducheon Fault, it was interpreted that high-density lower bedrock intermittently lifts close to the surface due to vertical tectonic movement accompanied by a flower structure. The fracture zone of the Dongducheon Fault is estimated that the width is about 200 m, the depth is at least 5 km, and the density is about 15% lower than the adjacent rocks. It is analyzed that the shallow earthquakes that occurred within 5 km depth was concentrated along the low-density En echelon fault fracture zone developed between the high-density rocks intruding close to the surface. Therefore, the earthquakes can be interpreted as the result that the north-south stress caused by the dextral tectonic movement of the Dongducheon Fault activated the En echelon fault in the northwest-southeast direction.

• Journal of the Korean Institute of Intelligent Systems
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• v.11 no.5
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• pp.406-412
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• 2001

In this paper, a new fuzzy single layer learning algorithm is proposed, which shows improved learning time and convergence property than that of the conventional fuzzy single layer perceptron algorithms. First, we investigate the structure of physiological neurons of the nervous system and propose new neuron structures based on fuzzy logic. And by using the proposed fuzzy neuron structures, the model and learning algorithm of Physiological Fuzzy Single Layer Perceptron(P-FSLP) are proposed. For the evaluation of performance of the P-FSLP algorithm, we applied the conventional fuzzy single layer perceptron algorithms and the P-FSLP algorithm to three experiments including Exclusive OR problem, the 3-bit parity bit problem and the recognition of car licence plates, which is an application of image recognition, and evaluated the performance of the algorithms. The experimentation results showed that the proposed P-FSLP algorithm reduces the possibility of local minima more than the conventional fuzzy single layer perceptrons do, and enhances the time and convergence for learning. Furthermore, we found that the P-FSLP algorithm has the great capability for image recognition applications.

• The Journal of Engineering Geology
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• v.21 no.1
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• pp.87-95
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• 2011

To provide regulatory standards and technical guides that are likely to be required for the Fault Monitoring System (FMS), soon to be installed and operated at the Shin-Wolsong NPP #1, 2 site, technical trend analysis was performed for currently operating geodetic and/or earthquake monitoring systems and activities worldwide, resulting in the identification of several items of concern regarding the design, installation, and operation of FMS at Korean sites. The items are as follows: 1) characterization of site-specific properties (including local noise), 2) selection of measuring instruments/design of appropriate sensitivity for the tectonic behavior of the target, 3) data/electricity backup system, 4) cross-checking and/or cross-referencing system to enhance data quality and credibility, 5) transparent data operation and open-to-the-public policy, and 6) long-term operation in a stable environment.