• Ocean and Polar Research
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• v.24 no.3
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• pp.249-253
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• 2002

There is a great deal evidence concerning crustal uplift, after deglaciation, in the vicinity of Syowa Station $(69^{\circ}S,\;39^{\circ}E)$ from tide gauge data, seismic evidence, raised beaches, marine terraces, etc. The geomorphological and tide gauge data show that the crustal uplift is going on around Syowa Station. Seismic observations at Syowa Station started in 1959. Phase readings of the earthquakes have been published by National Institute of Polar Research once a year since 1968, as one of the Data Report Series. Eighteen local earthquakes were detected on short period seismograms at Syowa Station in 1990-2000. The seismicity during the period from 1990 to 2000 was lower than that from 1987 to 1989 when epicenters of local earthquakes were determined by tripartite seismic array. Local earthquake activity corroborates the crustal uplif4 which is an intermittent phenomenon. Sea level falling of 4.5 mm/y was found using data in 1975-1992. This felling rate is consistent with the geomorphological data. A route for repeat leveling survey was established in East Ongul Island. No appreciable change of sea level was observed for the last 14 years. A dynamics of the crustal uplift around Syowa Station has been discussed using geomorphological data, ocean tide, and seismic and leveling data, which is estimated to be an intermittent phenomenon. When local seismic activity is high, the crustal uplift is estimated to be going on. On the contrary, the crustal uplift is in dormancy when the local seismicity is low. Repeated leveling measurements suggest no significant changes, which further supports the idea that the crustal uplift in offshore is not a tilt trend movement but a block movement.

• Economic and Environmental Geology
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• v.27 no.4
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• pp.397-409
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• 1994

The seemingly scattered plot of heat flow versus crustal thickness is explained by geodynamic processes and simple thermal relaxation in two contrasting tectonic elements. Elevated heat flow is characteristic of rift provinces where the crust is attenuated by stretching but also of orogenic belts where thrust tectonics thickens the crust and significantly enhances crustal heat production. With the progression of time, isostatic processes thin the thickened crust through uplift and erosion and thicken the rifted crust through subsidence and sedimentation. Heat flow relaxes to a value in equilibrium with background mantle heat flow.

• Economic and Environmental Geology
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• v.33 no.3
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• pp.217-228
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• 2000

We use spectral correlation method to analyze gravity and magnetic anomalies of Euiseong Sub-basin for distribution of rock facies and gelogic structures. The analysis reveals distinct polarity between gravity and magnetic anomaly correlation ; intermediate to mafic intrusives, extrusives, and the Tertiary basin shows positive gravity (+G) and positive magnetic (+M) correlation. Granitic gneiss and felsic volcanics negative gravity 9-G) and negative magnetic (-M) correlation. The Palgongsan granite, felsic to mafic extrusives and Mesozoic granites are characterized by -G and + M correlation. +G and -M correlations in the sedimentary formations are interpreted by uplift of pre-Cretaceous basement rocks . The + G and + M correlation characteristics in northeastern part of Euiseong Sub-basin including the Tertiary sedimentary basin result from the uplift of crustal materials. Major axes of spectrally correlated amomalies have mostly NW-SE or NE-SW directions. The former is due to the intrusives along strike-slip faults, and the latter which is observed in sedimentary formations is related to geological structures of basement associated new insight into the boundary between Euiseong and Milyang Sub-basin.

• The Journal of the Petrological Society of Korea
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• v.2 no.2
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• pp.104-121
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• 1993

Fission track (FT) thermochronological analyses on Mesozoic granites provide new information about cooling and uplift histories in Southeast Korea. Twenty-nine new FT sphene, zircon and apatite ages and seven track length measurements are presented for eleven granite samples. Measured mineral ages against assumed closure temperatures yield cooling rates for each sample. Relatively rapid (7-$15^{\circ}C$/Ma) and simple cooling patterns from the middle Cretaceouss (ca. 90-100 Ma) granites are caused mainly by a high thermal contrast between the intruding magma and country rocks at shallow crustal levels (ca. 1-2.5 km-depths). On the contrary, a slow overall cooling (1-$4^{\circ}C$/Ma) of the Triassic to Jurassic granites (ca. 250-200 Ma), emplaced at deep depths (>>9 km), may mainly depend upon very slow denudation of the overlying crust. The uplift history of the Triassic Yeongdeog Pluton in the Yeongyang Subbasin, west of the Yangsan Fault, is characterized by a relatively rapid uplift (~0.4 mm/a) before the total unroofing of the pluton in the earliest Cretaceous (~140 Ma) followed by a subsidence (~0.2mm/a) during the Hayang Group sedimentation. Stability of original FT zircon ages (156 Ma) and complete erasure of apatite ages suggest a range of 3 to 5.5 km for the basin subsidence. Since 120 Ma up to present, the Yeongyang Subbasin has been slowly uplifted (~0.04 mm/a). The FT age patterns of Jurassic granites both from the northeastern wing of the Ryeongnam Massif and from the northern edge of the Pohang-Kampo Block indicate that the two geologic units have been slowly uplifted with a same mean rate (~0.04 mm/a) since early Cretaceous. Estimates of Cenozoic total uplifts since 100 Ma are different: Ryeongnam Massif (~6 km)=Pohang-Kampo Block (~6 km)>Yeongyang Subbasin(~4 km).

• Journal of the Korean earth science society
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• v.32 no.7
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• pp.719-731
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• 2011

Based on the ICE-3G and ICE-5G ice models, we predicted the velocities of crustal uplift caused by Glacial Isostatic Adjustment (GIA) at 39 tide gauge sites operated by Korea Hydrographic and Oceanographic Administration (KHOA). We also divided the Korean peninsula in the ranges of $32-38.5^{\circ}N$ and $124-132^{\circ}E$ in $0.5^{\circ}{\times}0.5^{\circ}$ grids, and computed the GIA velocities at each grid point. We found that the average uplift rates due to GIA in South Korea were 0.33 and 1.21 mm/yr for ICE-3G and ICE-5G, respectively. Because the GIA rates were relatively high at ~1 mm/yr when the updated ice model ICE-5G was used, we concluded that the GIA effect cannot be neglected when we compute the absolute sea level (ASL) rates around the Korean peninsula. In this study, we corrected the ICE-5G GIA velocities from the relative sea level rates provided by KHOA and we computed the ASL rates at 13 tide gauge stations. As a result, we found that the average ASL velocity around the Korean peninsula was 5.04 mm/yr. However, the ASL rates near Jeju island were abnormally higher than the other areas and the average was 8.84 mm/yr.

• Ocean and Polar Research
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• v.26 no.3
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• pp.523-529
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• 2004

The seismic monitoring at Syowa Station$(69^{\circ}S,\;39^{\circ}E: SYO)$, located on the continental margin of the Eastern Dronning Maud Land, East Antarctica, began in 1959. Phase readings of the earthquakes have been reported since 1967 and have been annually published as part of the Data Report Series of the National Institute of Polar Research since 1968. An observation of a tripartite seismic network was carried out at SYO for a period of three years from 1987 to 1990. Epicenters of local earthquakes were determined for the first time by using the array network for the three-year period. Many different types of earthquakes, such as the mainshock-aftershock type, twin earthquake, earthquake swarms, etc., were detected during the period. After this, local events around SYO have been detected empirically from their waveforms recorded on seismograms. The seismic activity for the period of 1987-1990 was higher than that of the following decade. Earthquake epicenters, occurring during that period, were highly localized along the coast and in the central part of the $L\"{u}tzow-Holm$ Bay (LHB). Nine local earthquakes, recorded during the period of 1990-1996, showed many different types of events. The seismicity for the period of 1990-1996 was very low and the magnitudes ranged from 0.1 to 1.4. The locations of some events were determined by using the single station method for SYO, i.e., using the particle motions of the initial phase and S-P time. Two local events were detected in 1998 and one event in 2001. It would be estimated that the stress concentration was related to the glacial rebound around the LHB. Afterwards, we will be able to eventually examine the relationship between the seismicity around Antarctica and deglacial phenomena such as crustal uplift, and sea level change within the earth environmental system.

• The Journal of Engineering Geology
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• v.13 no.1
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• pp.107-127
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• 2003

After detailed geological mapping, structural and fracture-density data were collected and analyzed in the vicinity of Cheonseong and Jeongjok Mts., Gyeongsangnam-do. A extensive dextral strike-slip fault (Beopgi Fault) Parallel to Yangsan and Dongrae Faults, a dextral-transtensional-NW fault, and a few intermittent faults have been found in the study area. Based on strike and frequency, fracture system has been divided into three sets such as NNE-trending J1 ($NS-40^{\circ}E$), WNW-trending J2 ($N50^{\circ}-80^{\circ}W$), and ENE-trending J3 ($N60^{\circ}-90^{\circ}E$). According to analysis of fracture density, it is revealed as follows: (a) Jl is the combination of Y-, P-, and R-shear fractures due to the dextral strike-slip of the Beopgi Fault. (b) J2 is the preexisted fracture zone conducting the intrusion of granite. Two tensional fractures dipping to NNE and SSW respectively have been induced by intrusion of granite and followed crustal uplift. (c) J3 is the tensional fracture developed between Yangsan and Dongrae Faults having NNE trend and dextral strike-slip sense. This study aims to reduce environmental impact and insure stability of underground facilities and tunnels.

• The Journal of Engineering Geology
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• v.17 no.1 s.50
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• pp.27-40
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• 2007

Stratigraphy has been renewedly set up and the evolution of tectonic events related to basin formation has been exam-ined on the basis of fault-slip data analysis in the Tertiary Eoil and Waeup basins of the southeastern part of Korea. First of all, field mapping was carried out in detail for Tertiary formations and then paleostress analysis were peformed with more than 400 fault slip data collected from 11 sites in the Tertiary formations and the Yucheon Group. It is judged that both the Eoil and Waeup basins filled up with Tertiary deposits might be simultaneously formed in separate locations. The Janggi Group in the Eoil basin is divided into following stratigraphic units in ascending order: Gampo Conglomerte, Hongdeok Basalt, Nodongri Conglomerate and Yeondang Basalt, and the Bomkori Group in the Waeup basin: Waeupri Tuff; Andongri Conglomerate, Yongdongri Tuff and Hoamri Volcanic Breccia. Paleostress analysis by using striated faults reveals five sequential tectonic events: (1) NW-SE transtension (event I), (2) NW-SE transpression (event IIl), (3) NE-SW pure extension (event III), (4) N-S transpression (event IV) and (5) E-W pure compression (event V). Therefore, five sequential tectonic movements are closely associated with the formation and evolution of the Tertiary basins in the study area: tectonic event I of NW-SE extension is related to formation of the Tertiary basins during the late Oligocene to the Early Miocene, tectonic events II, III and IV caused the termination of the Tertiary basin opening and the crustal uplift in the study area, and tectonic event V upheaved the east coast or Korean Peninsula with compressive stress due to intense subduction of the Pacific plate into Asian continent since the Early Pliocene.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.14 no.2
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• pp.90-101
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• 2009

Analysis of multi-channel seismic reflection data from the Southern Ulleung Basin reveals that Plio-Quaternary section in the area consists of nine stacked sedimentary units separated by erosional unconformities. On the southern slope, these sedimentary units are acoustically characterized by chaotic seismic facies without distinct internal reflections, interpreted as debris-flow bodies. Toward the basin floor, the sedimentary units are defined by well-stratified facies with good continuity and strong amplitude, interpreted as turbidite/hemipelagic sediments. The seismic facies distribution suggests that deposition of Plio-Quaternary section in the area was controlled mainly by tectonic movement and sea-level fluctuations. During the Pliocene, sedimentation was mainly controlled by tectonic movements related to the back-arc closure of the East Sea. The back-arc closure that began in the Miocene caused compressional deformation along the southern margin of the Ulleung Basin, resulting in regional uplift which continued until the Pliocene. Large amounts of sediments, eroded from the uplifted crustal blocks, were supplied to the basin, depositing Unit 1 which consists of debris-flow deposits. During the Quaternary, sea-level fluctuations resulted in stacked sedimentary units (2-9) consisting of debris-flow deposits, formed during sea-level fall and lowstands, and thin hemipelagic/turbidite sediments, deposited during sea-level rise and highstands.

• The Journal of the Petrological Society of Korea
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• v.1 no.1
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• pp.49-57
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• 1992

Whole rock and mineral ages for the Jecheon Granite distributed in the Ogcheon Fold Belt were dated by three radiometric methods, and its thermal history was elucidated as follows, on the basis of isotopic age data. Rb and Sr isotopic compositions of three whole rock and seven mineral concentrates made an isochron of 202.7${\pm}$ 1.9 Ma with a strontium initial ratio of 0.7140. Different age data of twelve mineral concentrates agree closely with the retention temperature of each mineral in K-Ar and Fission Track methods. The Jecheon granitic magma was generated by partial melting of crustal materials (S-type), or by mixins between mantle and crustal materials, intruded into the katazone or mesozone (7∼9 km) of the Ogcheon Fold Belt, at least in the Early Jurassic (about 203 Ma), and then crystallized and cooled down rapidly from about 600$^{\circ}C$ to 300$^{\circ}C$ (more than 20$^{\circ}C$/Ma), owing to thermal differences between the magma and the wall-rock. During the Middle to Late Jurassic (190∼140 Ma), the cooling of the granite was likely to stop and keep thermal equilibrium with the wall-rock. The severe tectonism associated with igneous activities and active weathering on the surface in Early to Late Cretaceous time (140∼70 Ma) might have accelerated the granite pluton to uplift rapidly (40∼60 m/Ma in average) up to 3∼4 km and cooled down from 300$^{\circ}C$ to 200$^{\circ}C$ (1.4 $^{\circ}C$/Ma). The granite pluton was likely to keep different uplifting and cooling rate of about 120 m/Ma and 5$^{\circ}C$/Ma in average from the Late Cretaceous to Early Tertiary (70∼50 Ma), and about 60 m/Ma and 2$^{\circ}C$/Ma in average from about 50 Ma up to the present, respectively.