• The Korean Journal of Quaternary Research
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• v.15 no.1
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• pp.13-20
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• 2001

The Pollen analyses and the $^{14}C$-dating of the sediments of Moojechi bog were performed in order to study the vegetation history and the environmental changes of the southeasterm montane zone of Korea. These results show that the local pollen assemblage of the montane zone changed from lower upward cool-temperate northern/altimontane forest(MI) into cool-temperate central/montane forest(M II a) and cool-temperate souther $n_montane forest(M II b). Furthermore, In the case of the present cool temperature deciduous broad-leaved forests, its distribution would begin to be expanded from 8,000yr B.P., and its regional differentiation would be developed from 6,700yr B.P..P.

• Geophysics and Geophysical Exploration
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• v.14 no.3
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• pp.249-253
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• 2011

Based on intrinsic and scattering quality factor ($Q_i^{-1}$ and$Q_s^{-1}$) obtained from the seismic data of the southeastern Korean Peninsula, the expected coda quality factor (${Q_{Cexp}}^{-1}$) was theoretically calculated using multiple scattering model, and was compared with other quality factors such as $Q_i^{-1}$, $Q_s^{-1}$, and observed $Q_C^{-1}$ obtained by single scattering model. While the ${Q_{Cexp}}^{-1}$ values are typically comparable to the $Q_i^{-1}$ values, the $Q_C^{-1}$ values are different from the ${Q_{Cexp}}^{-1}$ values except for the higher frequency. Future works require to consider depth-dependent attenuation.

• The Korean Journal of Quaternary Research
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• v.18 no.1 s.22
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• pp.41-46
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• 2004

The fluvia(thalassostatic) terraces have been developed among the lower Yeongsan river, near the southwestern coastal region of Korean peninsula. These thalassostatic terraces could be classified into 3 surface, i. e., Yeongsan 32m, 18m, and 10m surface, in desending order, according to the relative heights from the river floor. Yeongsan 32m, 18m and 10m surfaces were corresponded to the mMT3, mLT1 and mLT2 surfaces of Choi(2003), respectively. It was revealed that the mLT1 surface was the marine terraces which had been formed in the Last Interglacial culmination period(oxygen isotope stage 5e) in the southeastern coast of Korean peninsula.

• The Journal of the Petrological Society of Korea
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• v.11 no.3_4
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• pp.169-181
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• 2002

Basic~intermediate dike swarms are pervasively developed in the east of the Ulsan Fault, SE Korea. Most of them intruded initially along the NS-trending extensional fractures which developed under EW extension during the East Sea opening in the Early Miocene (before about 17 Ma). The mean-strikes of the basic dikes intruding into the granites are more clockwise rotated in farther eastern side, i. e.$ N06^{\circ}$E, $Nl5^{\circ}$E, and $N37^{\circ}$E in the western side, in the just vicinities, and in the eastern side of the YBonil Tectonic Line (YTL), respectively. And the mean-strike of the basic dikes nearby shoreline is also most clockwise rotated ($N75^{\circ}$E in the Guryongpo Peninsula). The spatial variance indicates that the dikes, located only in the east of the YTL, experienced horizontal-clockwise rotation, and that the dikes in farther east from the YTL experienced more clockwise rotation. It is, thus, supported that the NNW dextral shear stress, generated by the spreading of the East Sea, was propagated toward inland from eastern continental margin of the Korean Peninsula, and that the YTL is an westernmost limit of the clockwise crustal rotations which are pervasively observed in the vicinities of the Miocene basins, SE Korea.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.6
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• pp.59-70
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• 2003

We estimated the spectrum decay parameter $\chi$ and the stress parameter ($\Delta$$\sigma$) in southeastern Korea. Especially, we propose a procedure to compute site-independent $\chi$$_{q}$ and dependent $\chi$$_{s}$ values, separately, This procedure is to use the coda normalization method for the computation of site independent Q or corresponding $\chi$$_{q}$ value as the first step followed by the next step, the computation of $\chi$$_{s}$ values for each site using the given $\chi$$_{q}$ value evaluated at the first step, For the estimation of stress parameter, we used seismic data monitored from three earthquakes occurred near Gyeongju in 1999 with the method of Jo and Baag, In addition, we simulated strong ground motion using the $\chi$ value and the stress parameter, In this case, we calculated the $\chi$ value with conventional method. The $\chi$ value of 0.016+0.000157R and the stress parameter of 92-bar was applied to the stochastic simulation, At last, we derived seismic attenuation equation using results of the stochastic prediction, and compared these results with some others reported previously.ported previously.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.10a
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• pp.27-32
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• 2000

Microearthquake records with magnitude 2.6~3.1 recorded in the southeastern part of the Korean peninsula during 1994~1998 are analyzed. Total of 42 records consisted of 12 events instrumented at 7 stations. The response spectra with the above data shows that the frequency range of the dominant response is about 10~25Hz and are compared with the standard response spectrum. The result implies that the characteristics of the microearthquake ground motion differ from those of standard response spectrum presented in US NRC Reg. Guide 1.60 especially at higher frequencies.

• The Korean Journal of Quaternary Research
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• v.32 no.1_2
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• pp.1-29
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• 2018

We investigated the seasonal variation of diatoms from the modern bottom floor sediments of the reservoirs distributed in the southern part of the Korean Peninsula. The studied reservoirs include each three reservoirs from Southeastern part, Central Southern part and Southwestern part, respectively, to compare the dominant diatom assemblages that are ecologically controlled by local environments. In the Southeastern region, Aulacoseira spp., Fragilaria crotonensis, Fragilaria tenera, Gomphonema gracile, G. parvulum and Gyrosigma attenuatum were dominant species. Aulacoseira spp., Cymbella tumida, Cymbella turgidula, Diploneis finnica and Fragilaria crotonensis were dominant taxa in the Central Southern regions. In the southwestern region, Aulacoseira spp., Fragilaria crotonensis, Gomphonema parvulum and Stenopterobia curvular were predominated. Of which Aulacoseira spp. were predominant species at all reservoirs. In addition most of dominants are saproxenous taxa living in the clean water area, and the water quality of these reservoirs is considered to be less polluted water. As a result of seasonal comparison of diatom productivity, the first productivity is higher in summer than in winter. However, diatom valve abundance in the southeastern reservoirs was fewer from the samples collected at May than February.

• The Journal of the Petrological Society of Korea
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• v.11 no.3_4
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• pp.182-199
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• 2002

We attempted to show the evolution of the magma and the geochemical characteristics of dikes and dike swarms by using the petrographic and geochemical data from 287 dikes, SE Korea. The dikes can be divided into mafic, intermediate, and felsic dikes in the field. And each of them is subdivided into three groups, two groups, and two groups, respectively. The group (I) among the mafic dikes most pervasively occurs and are distributed in both sides of the Yeonil Tectonic Line (YIL), which petrographic and geochemical characteristics are the same. These facts thus, strongly support the results of the previous studies which showed that they were intruded contemporaneously and that YTL was a main tectonic line which restricted the crustal clockwise rotation during the Early Miocene. The geochemical characteristics are discriminated according to the seven groups divided petrographically. The mafic, intermediate and felsic dikes belong to basalt and basaltic andesite, andesite and facile, and rhyolite, respectively, and the magmas mostly belong to calc-alkaline series. The geochemical data indicate that there were the fractional crystallizations of olivine, clinopyroxene, and plagioclase in the mafic dikes. And the content of characteristic elements and tectonic discrimination diagrams show that the dikes were formed from the magma related to the subduction of plate and that the tectonic setting was related to orogenic volcanic arc.

• The Journal of the Petrological Society of Korea
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• v.13 no.2
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• pp.64-80
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• 2004

The Miocene volcanic rocks in the Eoil Basin, which is one of the pull-apart basins in the southeastern Korean Peninsula, are bimodal in composition: felsic (67.2-70.5wt.% SiO$_2$) and mafic(49.3-55.2wt.% SiO$_2$). The bimodal volcanic activities in the basin appear to be closely associated with the basin development. The volcanic rocks are intercalated with thick Files of sedimentary sequence. They show evidence of magma mixing. which has produced mafic and felsic volcanic rocks. We are able to identify the petrographic characteristics (disequilibrium phenocryst assemblages) of the volcanic rocks that were mixed. In basaltic lava, phenocrysts of olivine and orthopyroxene coexist with corroded quartz phenocryst. Dacitic to rhyolitic welded ash-flow tuff contains phenocrysts of clinopyroxene and orthopyroxene. It suggests that phenocryst disequilibrium have been affected and mixed by magmas, which have different compositions.

• Journal of The Geomorphological Association of Korea
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• v.25 no.4
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• pp.63-75
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• 2018

The lower marine terrace 1 and 2 surfaces distributed between Ulsan and Pohang coast in the southeastern coast of the Korean penninsula have been correlated with MIS 5e and 5a (or 5c) by amino acid dates, 14C dates, wide-spread tephra correlation and pollen analysis respectively. In this study, to test the reliability of the OSL method for the estimation of the numerical burial age of marine sediment deposits, we analyzed the samples from the marine terraces which have been known as typical marine terraces formed during MIS 5e and MIS 5a in the above-mentioned coast. The burial ages of the marine deposit of the lower marine terrace 1 and 2, with paleoshoreline altitudes of 18m to 19m and 10m to 11m respectively, both showed about the same age of 60 ka BP. The lower marine terraces 1 and 2, however, were divided into two terrace surfaces by a clear terrace cliff. Besides, the OSL dates of the lower and upper parts of the lower marine terrace 2 of the Bonggil coast showed the reversed burial ages. In the lower marine terrace 1 of the Sanhari coast, almost the same burial ages were derived from both the lower part (marine rounded gravel layer) and the upper part (terrestrial angular gravel layer) of the terrace deposit. Therefore, at the present time, judging from only the OSL dates measured in this study, it could be argued that the OSL method is not the best for the estimation of forming periods of the lower marine terraces 1 and 2 and their classification.