• Title, Summary, Keyword: 오대산지진

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A Study for Earthquake Parameter of Odaesan Earthquake (오대산지진(2007/01/20)의 지진원 특성에 관한 연구)

  • Kim, Jun-Kyoung
    • The Journal of Engineering Geology
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    • v.17 no.4
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    • pp.673-680
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    • 2007
  • The seismic source parameters of the Odaesan earthquake on 20 January 2007, including focal depth, focal mechanism, magnitude, and source characteristics, are analysed using seismic moment tensor inversion. The Green's function for different 3 crust models representing the southern Korean Peninsula are used. Final results show that the event, considering 6 seismic moment tensor elements, is caused by the typical strike slip fault with nearly NNE strike. The focal depth is estimated to be about 11km and 6 seismic moment tensor elements with 7.2% CLVD value shows typical double couple seismic source. The consistent characteristics of the strike and epicenter of the event with Odaesan fault imply that Odaesan earthquake is mainly caused by movement of the Odaesan fault.

Characteristics of the Point-source Spectral Model for Odaesan Earthquake (M=4.8, '07. 1. 20) (오대산지진(M=4.8, '07. 1. 20)의 점지진원 스펙트럼 모델 특성)

  • Yun, Kwan-Hee;Park, Dong-Hee
    • Geophysics and Geophysical Exploration
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    • v.10 no.4
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    • pp.241-251
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    • 2007
  • The observed spectra from Odaesan earthquake were fitted to a point-source spectral model to evaluate the source spectrum and spatial features of the modelling error. The source spectrum was calculated by removing from the observed spectra the path and site dependent responses (Yun, 2007) that were previously revealed through an inversion process applied to a large accumulated spectral dataset. The stress drop parameter of one-corner Brune's ${\omega}^2$ source model fitted to the estimated source spectrum was well predicted by the scaling relation between magnitude and stress drop developed by Yun et al. (2006). In particular, the estimated spectrum was quite comparable to the two-corner source model that was empirically developed for recent moderate earthquakes occurring around the Korean Peninsula, which indicates that Odaesan earthquake is one of typical moderate earthquakes representative of Korean Peninsula. Other features of the observed spectra from Odaesan earthquake were also evaluated based on the commonly treated random error between the observed data and the estimated point-source spectral model. Radiation pattern of the error according to azimuth angle was found to be similar to the theoretical estimate. It was also observed that the spatial distribution of the errors was correlated with the geological map and the $Q_0$ map which are indicatives of seismic boundaries.

Fault rupture directivity of Odaesan Earthquake (M=4.8, '07. 1. 20) (오대산지진(M=4.8, '07. 1. 20)의 단층파열방향성)

  • Yun, Kwan-Hee
    • Geophysics and Geophysical Exploration
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    • v.11 no.2
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    • pp.137-147
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    • 2008
  • Fault rupture directivity of the Odaesan earthquake, which was inferred to be the main cause of the high PGAvalue (> 0.1 g) unusually observed at the near-source region, was analyzed by using the data from the nearby (R < 100 km) dense seismic stations. The Boatwright's method (2007) was adopted for this purpose in which the azimuth and takeoff angle of the unilateral rupture directivity function could be estimated based on the relative peak ground-motions of seismic stations resulting from the nature of the rupture directivity. In this study, the approximate values of the relative peak ground-motions was derived from the difference between the log residuals of the point-source spectral model (Boore, 2003) for the main and secondary events based on the Random Vibration Theory. In this derivation, the spectral difference for a frequency range between the source corner frequencies of main and secondary events was considered to reflect only the effect of the fault directivity. The inversion result of the model parameters for the fault directivity function showed that the fault-plane of NWW-SEE direction dipping steeply to the North with high rupture velocity near upward in SE direction is responsible for the observed high level of ground-motion at the near-source region.

Large Ground Motion Related to Crustal Structure in Korea (한반도 지각 구조로 인한 이상 강진동 관측 및 해석)

  • Kim, Kwang-Hee;Kang, Su-Young;Min, Dong-Joo;Suk, Bong-Chool;Ryoo, Yong-Gyu
    • Journal of the Korean earth science society
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    • v.29 no.7
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    • pp.559-566
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    • 2008
  • Ground shaking recorded during the January 20, 2007, $M_L$ 4.8 Odaesan earthquake (Korea) were used to investigate the role of the crustal structure in producing a strong ground motion, which includes the identification of the phases responsible for the strong ground motion and their implications for seismic hazard assessment. Analyses of strong-motion data together with waveform simulation revealed that critical and post-critical reflections from the crust-mantle boundary are responsible for the abnormal ground motions. This result demonstrates that the crustal structure should be taken into consideration in studies of seismic hazard mitigation even in the areas of relatively low seismicity.

Analysis of Response Spectrum of Ground Motions from Odaesan Earthquake (2007/01/20) (오대산지진(2007/01/20) 관측자료를 이용한 응답스펙트럼 분석)

  • Kim, Jun-Kyoung
    • Journal of the Korean earth science society
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    • v.28 no.7
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    • pp.871-877
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    • 2007
  • The response spectrum was studied using the observed pound motion from the Odaesan Earthquake (2007/01/20), and then the results were compared to the seismic design response spectra (Reg Guide 1.60) applied to the domestic nuclear power plants. For the response spectrum analysis, 21 horizontal and 8 vertical observed Pound motions were used for normalization and statistical analysis. The results showed that the MPOSD (Mean Plus One Sigma Standard Deviation) response spectra above 10 Hz revealed higher values than the design response spectra and those below 10 Hz revealed much lower values fur both horizontal and vertical response spectra. These results suggest that the response spectra (Reg. Guide 1.60), used as seismic design code for nuclear facilities in Korea, especially above about 10 Hz, should be reexamined fur apllication to the nuclear power plants structures operated in the Korean Peninsula.

Analysis of Site Amplification of Seismic Stations using Odesan Earthquake (오대산지진 자료를 이용한 국내 지진관측소 부지의 지반증폭특성 연구)

  • Kim, Jun-Kyoung
    • Journal of the Earthquake Engineering Society of Korea
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    • v.13 no.1
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    • pp.27-34
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    • 2009
  • Site amplification should be considered in order to estimate Soil-Structure Interaction (SSI), seismic source and attenuation parameters with a greater degree of reliability. The horizontal to vertical (H/V) ratio technique, originally proposed by Nakamura (1989), has been applied to analyze the surface waves in microtremor records. Recently, its application has been extended to the shear wave energy of strong motion in order to study the site transfer function. The purpose of this paper is to estimate the H/V spectral ratio using the observed data from 9 seismic stations distributed within the Southern Korean Peninsula, from the Odesan earthquake (2007/01/20). The results show that most of the stations have more stable amplification characteristics in a low frequency band than in a high frequency band. However, each seismic station showed its own characteristic resonant frequency and low and high frequency. The resonant frequency at each station should be estimated carefully, because the quality of seismic data is dependent on the resonant frequency. It can be obtained more reliable results of seismic source and attenuation parameters, if seismic ground motions which deconvolved from site transfer function is used. The site amplification data from this study can be used to generally classify the sites within the Southern Korean Peninsula.

Relation of Intensity, Fault Plane Solutions and Fault of the January 20, 2007 Odaesan Earthquake (ML=4.8) (2007년 1월 20일 오대산 지진(ML=4.8)의 진도, 단층면해 및 단층과의 관계)

  • Kyung, Jai-Bok;Huh, Seo-Yun;Do, Ji-Yong;Cho, Deok-Rae
    • Journal of the Korean earth science society
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    • v.28 no.2
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    • pp.202-213
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    • 2007
  • The Odaesan earthquake $(M_L=4.8)$ occurred near Mt. Odae, Jinbu-Myon, Pyongchang-Gun, Kangwon Province on January 20, 2007. It has a shallow focal depth about 10 km. Its felt area covers most of the southern peninsula except some southern and western inland area. The maximum MM intensity was VI in the areas including Jinbu, Doam, Kangreung, Jumunjin, and Pyongchang. In these areas, there was a very strong shaking that caused several cracks on the walls of buildings and houses, slates falling off the roof, tiles being off the wall, things falling off the desk, and rock falling from the mountains. In order to get fault plane solutions, grid searches were performed by fitting distributions of P-wave first-motion polarities and SH/P amplitude ratios for each event. The results showed that the main shock represented right-lateral strike-slip sense and two aftershocks, reverse sense. It seems that the seismogenic fault may be the NNE-SSW trending Weoljeongsa fault near the epicenter based on the distribution of epicenters (foreshock, main shock, and aftershocks), damage area, and fault plane solution. The distribution of the epicenters indicates that the length of the subsurface rupture is estimated to be about 2 km.

The Behaviors of Earthquake Monitoring System for Gyungbu High Speed Railroad on the Odaesan Earthquake (오대산지진 시 경부고속철도 지진감시시스템 거동)

  • Kim, Dae-Sang;Kim, Sung-Il;Choi, Su-Hyun;You, Won-Hee
    • 한국방재학회:학술대회논문집
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    • pp.537-540
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    • 2008
  • This paper reviews the operation standards and manuals of earthquake monitoring system for Gyungbu high speed railroad. The domestic earthquake monitoring system detects the acceleration data at the locations of lower part of pier and deck of viaducts and bridges, not like foreign system to do the surface ground accelerations. For the purpose of evaluating the behaviors of the domestic earthquake monitoring system, measured acceleration data on the Odaesan earthquake at Iwon viaduct were analysed. The values of maximum acceleration level of the viaduct were increased from 0.0089g(EW component) of the lower part of pier to 0.014g(EW component) on the deck of the viaduct. And also the predominant periods and frequencies were analysed by the frequency domain analysis.

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