• Journal of Conservation Science
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• v.37 no.6
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• pp.617-625
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• 2021

Daegokcheon Stream in Daegok-ri, Ulju-gun, is an area with a developed valley and bedrock from Gajisan Provincial Park to the confluence of the Taehwa River across the Yangsan Fault. To measure the rock of Bangudae petroglyphs, the mineralogical weathering, joints, and scours or cavities at the bottom were confirmed. The measurement was carried out for a short period of time on the joint of the bedrock on which the Bangudae petroglyphs were engraved. Compared to the measured value obtained using existing optical fiber (Ch4 150 ㎛), a displacement value of 300 ㎛ was obtained using the non-attached, non-contact type of measuring instrument. In the future, it is inferred that this instrument could be used for various cultural properties if the HSV-value suitable for illuminance and various measurement experiences are stored.

• Economic and Environmental Geology
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• v.52 no.6
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• pp.519-528
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• 2019

In 2017, Korea Institute of Geoscience and Mineral Resources (KIGAM) has excavated a trench at Yongjang-li in the city of Gyeongju to examine the evidence of fault movement related with the 2016 earthquake in unconsolidated sediments. In the trench profile, the author has observed the features of ongoing soil-forming processes and groundwater movement overlapped on the sedimentary layers. The soil formation was in its initial stage, and most of the original sedimentary layers could be observed. The color changes depending on the redox conditions and by the Mn/Fe oxide precipitation, however, were the most significant features obscuring sedimentary records. The dark Mn oxide precipitates formed at the groundwater levels often concealed the sedimentary unit boundaries. The groundwater levels varied depending on the particle sizes of the sedimentary layers contacting the groundwater, and the Mn oxide precipitates have formed at varying depths. The groundwater could move upward along the narrow pores in the fine-textured sedimentary layer more than a few meters showing the gray color indicating a reducing condition for iron.

• Economic and Environmental Geology
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• v.51 no.5
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• pp.439-453
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• 2018

The Eocene Gyeongju granitoids in SE Korea are alkali feldspar granite (AGR), biotite granite (BTGR), and hornblende biotite granodiorite (HBGD) along Yangsan fault and Ulsan fault. According to their geochemical characteristics, these granitoids are classified as A-type (AGR) and I-type (BTGR and HBGD) granitoids, and regarded that were derived from same parental magma in upper mantle. The hornblende and biotite of AGR as an interstitial phase indicate that influx of F-rich fluid during the crystallization of AGR magma. AGR is enriched LILE (except Sr and Ba) and LREE that indicate the influences for subduction released fluids. The highest HFSE contents and zircon saturation temperature of AGR among the Eocene Gyeongju granitoids may indicate that it was affected by partial melting rather than magma fractionation. These characteristics may represent that the high F contents of AGR was affected by F-rich fluid derived from the subducted slab and partial melting. It corresponds with the results of the REE modeling and the dehydrated fluid component (Ba/Th) modeling showing that AGR (A-type) was formed by the partial melting of BTGR (I-type) with the continual influx of F-rich fluid derived from the subducted slab.

• The Journal of Engineering Geology
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• v.34 no.1
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• pp.1-12
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• 2024

South Korea's mining industry was actively developed until 1980, but subsequent declining profitability forced many mines to close. Most of the abandoned mines are susceptible to persistent subsidence because of the length of time since mining ceased. Accurate prediction of the locations and times of subsidence is difficult; therefore, this study aims to apply continuum analysis to past cases of subsidence to establish a method of predicting the location and magnitude of future subsidence. The study area is an area of ○○ mining located between the Yangsan fault zone and the Moryang fault zone, in which three subsidence events occurred between 2005 and 2009. Drilling surveys and electrical resistivity surveys were performed at subsidence sites determined the distribution of strata, and through laboratory tests obtained the physico-mechanical properties of the rock. Numerical analysis of the results found that the plastic status area includes the areas of actual subsidence and that continuum analysis can also be used to predict the location and magnitude of subsidence caused by mine goaf.

• The Journal of the Petrological Society of Korea
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• v.27 no.3
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• pp.153-171
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• 2018

This study focuses on the investigation of geologic distribution and stratigraphy in the eastern part of Yeongdeok-gun, based on Lidar imaging, detailed field survey, microscopic observations, SHRIMP and LA-MC-ICPMS U-Pb age dating, and a new geological map has been created. The stratigraphy of the study area is composed of the Paleoproterozoic metamorphic rocks consisting of banded gneisses of sedimentary origin and schists ($1841.5{\pm}9.6Ma$) of volcanic origin, Triassic Yeongdeok plutonic rocks ($249.1{\pm}2.3Ma$) and Pinkish granites ($242.4{\pm}2.4Ma$), Jurassic Changpo plutonic rocks ($193.2{\pm}1.9Ma{\sim}188.8{\pm}2.0Ma$) and Fine-grained granites ($192.9{\pm}1.7Ma$), Formations [Gyeongjeongdong Fm, Ullyeonsan Fm. (~108 Ma), Donghwachi Fm.] of the Early Cretaceous Gyeongsang Supergroup and acidic volcanic rocks and dykes erupted and intruded in the Late Cretaceous, Miocene intrusive rhyolitic tuffs ($23.1{\pm}0.2Ma{\sim}22.97{\pm}0.13Ma$) and sedimentary rocks of the Yeonghae basin, and the Quaternary sediments. The Triassic Pinkish granites, Jurassic Changpo plutonic rocks and Fine-grained granites are newly defined plutonic rocks in this study. Miocene intrusive rhyolitic tuffs bounded by the Yangsan Fault, which was first discovered in the north of Pohang city, are believed to play an important role in the understanding of the Miocene volcanic activity and the crustal deformation history on the Korean Peninsula. It is confirmed that The NNE-SSW-striking Yangsan Fault penetrating the central part of the study area and branch faults are predominant in the dextral movement and cutting all strata except the Quaternary sediments.

• The Journal of the Petrological Society of Korea
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• v.9 no.2
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• pp.70-83
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• 2000

The purpose of this study is to identify the petrographic and geochemical characteristics of four granitic masses and clanfy for the origin and relationship among the masses. These granitic rocks are distributed in the eastern part of Yangsan fault in the Kyongsang basin, southeastern part of Korea. Based on the mineralogy and texture, the granitic rocks are divided into three facies; granodiorite, porphyritic fine-grained granite, and equigranular granite. According to the result of modal analysis, northern part and most of the southern part of Daebon granitic rocks are plotted in granodiorite field and the rest part of the xocks are plotted in granite field. These granitic rocks belong to the sub-alkaline series, and are subdivided into calc-alkaline series. The rare earth elements normalized bv chondrite show LREE is more enriched than HREE and the lowest values in O-w m- i t e and Daebon equigranular granite. The crystallization pressures and temperatures of minimum melt compositions of granitic rocks estimated from the study area are about 0.5-1 kbar and $700~820^{\circ}C$, respectively. Referring to the petrographic characteristics, geochemical data and radiogenic age data, Oyu granite was emplaced in the Paleocene, but Daebon granodiorite, Sanseo porphyritic granite, and Hoam equigranular granite are co-magmatic differentiation products, were emplaced in the Eocene.

• Journal of the Korean earth science society
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• v.22 no.6
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• pp.500-511
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• 2001

For the southeastern Korea aound the Yangsan fault we measured Q$_P^{-1}$ and Q$_S^{-1}$ simultaneously by using the extended coda-normalization method for seismograms registered at 9 stations deployed by KIGAM. We analyzed 707 seismograms of local earthquakes that occurred between December 1994 and February 2000. From seismograms, bandpass filtered traces were made by applying Butterworth filter with frequency-bands of 1${\sim}$2, 2${\sim}$4, 4${\sim}$8, 8${\sim}$16 and 16${\sim}$32 Hz. Estimated Q$_P^{-1}$ and Q$_S^{-1}$ values decrease from (7${\pm}$2)${\times}$10$^{-3}$ and (5${\pm}$4)${\times}$10$^{-4}$ at 1.5 Hz to (5${\pm}$4)${\times}$10$^{-3}$ and (5${\pm}$2)${\times}$10$^{-4}$ at 24 Hz, respectively. By fitting a power-law frequency dependent to estimated values over the whole stations, we obtained 0.009 (${\pm}$0.003)f$^{-1.05({\pm}0.14)$ for Q$_P^{-1}$ and 0.004 (${\pm}$0.001)f$^{-0.75({\pm}0.14)$) for Q$_S^{-1}$, where f is frequency in Hz.

• The Journal of the Petrological Society of Korea
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• v.24 no.1
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• pp.11-24
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• 2015

In this study, the stone used for three storied pagoda of Bulguksa Temple, which is easy to access due to works for dismantle and restore will be analyzed on the basis of petrographic study, magnetic susceptibility, and ${\gamma}$-ray spectrometer, and identify petrographic characteristics. Also we will select candidate areas of fresh rock to change the stone used for three storied stone pagoda as from its provenance is presumed. According to the results of visual inspection, the stones used for the three storied stone pagoda are similar to the features of Namsan granite, which is distributed around Gyeongju-si, and when it comes to the section of the stupa finial, the features of all the parts from the stupa finial is similar to Namsan granite except for the section of Jeweled cover. On the other hand, the color, the composition, and the mineral size of the stones in the section from the part of jeweled cover are similar to Tohamsan granite. As a result of none-destruction inspection, it seems that the stones used for the three stories stone pagoda except for the section of jeweled cover are similar to the values for the magnetic susceptibility and the ${\gamma}$-ray spectrometer. On the other hand, Jeweled cover and the values of Tohamsan granite are alike. Namsan granite is appropriate in case that the stone used for three storied stone pagoda must be replaced to fresh rock because of damage by weathering. Meanwhile, Namsan granite is seperated from Yangsan fault. Due to this fact, Namsan granite appears to not only Mt. Namsan in Gyeongju, but also Dongcheon-dong, Gyeongju, and Huenggok-ri, Pohang. As a result, these two areas are suitable to the candidate area to change the stone used for three storied stone pagoda.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.38 no.6
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• pp.697-705
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• 2020

This paper deals with an analysis of crustal movement for the sourthern part of Korean peninsula using GNSS (Global Navigation Satellite System) data. An earthquake of more than 5.0 occurred in the southeastern region of the Korean Peninsula, and it is necessary to evaluate the risk of earthquakes in various ways.In order to reveal long-term tectonic movement patten in Pohang and Gyeongju provinces, we derived crustal movement parameters related with elastic theory. We used GAMIT/GLOBK for analyzing seven-year interval GNSS data of CORS (Continuously Operating Reference Stations). The azimuth of velocity vectors trended generally about 110° with an mean magnitude of 31mm/yr.The main characteristics of the strain change for seven-year in Korea obtaind from our study. Direction of the principal axis of the maximum compression is ENE-WSW as a whole, through there are some exceptions. The mean rate of the maximum shear strain change is (0.11±0.07)μ/yr, that is approximately one third that of Chubu district, Central Japan. Taking into account our results, the mean rate of maximum shear in southern part of Korean peninsula is considered as reasonable. The mean azimuth of principal strain is about (85.4°±26.8°). There are some exceptions of azimuth because the average azimuth differ from the left and right side in Yangsan fault which are about (73.2°±21.5°) and (105.2°±17.0°) respectively, It is noteworthy that the high seismicity areas in the southern part of Korea peninsula almost coincides with the area of large strain rate. As a conclusion, it could be stated that the our study represents the characteristics of crustal deformation in the southern part of peninsula, and contributes to the researches on earthquake disaster management.

• The Journal of Engineering Geology
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• v.30 no.4
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• pp.589-602
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• 2020

As can be seen in many earthquakes, liquefaction causes differential settlement, which sometimes produces serious damages such as building destruction and ground subsidence. There are many possible active faults near the Busan city and the Yangsan, Dongrae, and Ilgwang faults among them pass through the city. The Busan city is also located within the influence of recent earthquakes, which occurred in the Gyeongju, Pohang, and Kumamoto (Japan). Along the wide fault valleys in the city, the Quaternary unconsolidated alluvial sediments are thickly accumulated, and the reclaimed lands with beach sediments are widely distributed in the coastal area. A large earthquake near or in the Busan city is thus expected to cause major damage due to liquefaction in urban areas. This study conducted an assessment of the liquefaction hazard according to seismic recurrence intervals across the Busan city. As a result, although there are slight differences in degree depending on seismic recurrence intervals, it is predicted that the liquefaction potential is very high in the areas of the Nakdonggang Estuary, Busan Bay, Suyeong Bay, and Songjeong Station. In addition, it is shown that the shorter the seismic recurrence interval, the greater difference the liquefaction potential depending on site periods.