• Title/Summary/Keyword: site amplification ratio

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Characteristics of Site Amplification of the Broad-band Seismic Stations in Korea (국내 광대역 지진관측소의 부지증폭 특성)

  • Kim, Seo-Young;Kim, Sung-Kyun
    • Journal of the Korean earth science society
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    • v.30 no.7
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    • pp.810-823
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    • 2009
  • One of the critical factors in accurate determination of earthquake source parameters, and in prediction of seismic hazards is the detailed information related to the site amplification characteristics. The site amplification characteristics of the broad-band seismic stations in Korea were estimated as a function of frequency in the range of 0.2 to 20 Hz. A total of 1275 seismograms recorded from 43 earthquakes observed from 2003 to 2008 in the southern Korean Peninsula were used. It was found that the site amplification ratios for 28 stations estimated from the inversion of the ground motion model were approximately concordant with those obtained from the horizontal-to-vertical (H/V) spectral ratio except for some stations. The spectral site amplification characteristics obtained in this study did not show any considerable spatial distribution. It revealed to be largely correlated with the degree of weathering rather than the basement rock type. Considering the spectral site amplification ratio, 28 broad-band stations were classified into four groups and the characteristics of each group were described in the text.

The Dynamic Basement Amplification Characteristics of a Dam Site using a Reference Site Method (기준관측소 방법을 이용한 댐체 기반암의 동적 지반증폭특성)

  • Wee, Soung-Hoon;Kim, Jun-Kyoung;Yoo, Seong-Hwa
    • Journal of the Korean earth science society
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    • v.38 no.2
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    • pp.161-171
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    • 2017
  • Observed ground motions are composed of three factors such as, seismic source, attenuation, and site amplification effect. Among them, the site amplification characteristics should be considered significantly when estimating seismic source and attenuation characteristics with more confidence. The site effect is also necessary when estimating not only seismic hazard in seismic design engineering but also rock mechanical properties. This study uses the method of H/V spectral ratio of observed ground motion between target site and reference site called a reference site method. In addition to using the vertical Fourier spectrum of the reference site, we try out the horizontal Fourier spectrum as a new method in this study. We analyze H/V spectral ratio of six ground motions respectively, observed at four sites close to Yedang Reservoir. We then compare site amplification effects at each site using 3 kinds of seismic energies including S waves, Coda waves energy, and background noise. The results suggest that each site showed similar site amplification patterns in S waves and Coda waves energy. However, the site amplification of background noise shows much different characteristics from those of S waves and Coda wave energy, which suggests that the background noises at each site have their own developing mechanism. Each station shows its own characteristics of specific resonance frequency and site amplification properties in low, high and specific resonance frequency ranges. Comparison of the method used in this study to the others that used different methods can provide us with more information about the dynamic amplification of a site characteristics and site classification.

A Comparison Study of the Amplification Characteristics of the Seismic Station near Yedang Reservoir using Background Noise, S-wave and Coda wave Energy (배경잡음, S파 및 Coda파 에너지를 이용한 예당저수지 인근부지의 지반증폭 특성에 관한 비교 연구)

  • Wee, Soung-Hoon;Kim, Jun-Kyoung;Yoo, Seong-Hwa;Kyung, Jai-Bok
    • Journal of the Korean earth science society
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    • v.36 no.7
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    • pp.632-642
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    • 2015
  • Seismograms are composed of 3 characteristics, that is, seismic source, attenuation, and site amplification. Among them, site amplification characteristics should be considered significantly to estimate seismic source and attenuation characteristics with more confidence. This purpose of this study is to estimate the site amplification characteristics at each site using horizontal to vertical (H/V) spectral ratio method. This method, originally proposed by Nakamura (1989), has been applied to study the surface waves in microtremor records. It has been recently extended to the shear wave energy of strong motion and applied to the study of site amplification. This study analyzed the H/V spectral ratio of 6 ground motions respectively using observed data from 4 sites nearby in Yedang Reservoir. And then, site amplification effects at each site, from 3 kinds of seismic energies, that is, S waves, Coda waves energy, and background noise were compared each other. The results suggested that 4 sites showed its own characteristics of site amplification property in specific resonance frequency ranges (YDS: ~11 Hz, YDU: ~4 Hz, YDD: ~7 Hz). Comparison of this study to other studies using different analysis method can give us much more information about dynamic amplification of domestic sites characteristics and site classification.

Amplification based on shear wave velocity for seismic zonation: comparison of empirical relations and site response results for shallow engineering bedrock sites

  • Anbazhagan, P.;Aditya, Parihar;Rashmi, H.N.
    • Geomechanics and Engineering
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    • v.3 no.3
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    • pp.189-206
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    • 2011
  • Amplification based on empirical relations is widely used for seismic microzonation of urban centers. Amplifications are used to represent the site effects of a particular soil column. Many empirical correlations are available to estimate the amplification of seismic waves. These correlations are based on the ratio of shear wave velocity of foundation/rock to soil velocity or 30 m equivalent shear wave velocity ($Vs^{30}$) and are developed considering deep soil data. The aim of this work is to examine the applicability of available amplification relations in the literature for shallow engineering bedrock sites by carrying out site response studies. Shear wave velocity of thirteen sites having shallow engineering bedrock have been selected for the study. In these locations, the depth of engineering bedrock (> 760 ${\pm}$ 60 m/s) is matched with the drilled bore hole. Shear wave velocity (SWV) has been measured using Multichannel Analysis of Surface Wave survey. These sites are classified according to the National Earthquake Hazards Reduction Program (NEHRP) classification system. Amplifications for an earthquake are arrived for these sites using empirical relations and measured SWV data. Site response analysis has been carried out in SHAKE using SWV and using synthetic and real earthquake data. Amplification from site response analysis and empirical relations are compared. Study shows that the amplification arrived using empirical relations does not match with the site response amplification. Site response amplification is much more than empirical values for same shear wave velocity.

A Comparison Study of the Site Amplification Characteristics and Seismic Wave Energy Levels at the Sites near Four Electric Substations (4개 변전소시설 부지 인근관측소의 지반증폭 특성 및 파형에너지 수준 비교 연구)

  • Yoo, Seong-Hwa;Kim, Jun-Kyoung;Wee, Soung-Hoon
    • Journal of the Korean earth science society
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    • v.37 no.1
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    • pp.40-51
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    • 2016
  • The problem has been pointed out that the domestic design response spectrum does not reflect site amplification, particularly in the high frequency bands, including the fact that site specific response spectrum from the observed ground motions appears relatively higher than design response spectrum. Among various methods, this study applied H/V spectral ratio of ground motion for estimating site amplification. This method, originated from S waves and Rayleigh waves, recently has been extended to Coda waves and background noise for estimating site amplification. For limited time of periods, 4 electric substation sites had operated seismic stations at two separate locations (bedrock and borehole) within each substation site. H/V spectral ratio of S wave, Coda wave, and background noise, was applied to 36 accelerations of 3 macro earthquakes (Odaesan, Jeju and Gongju earthquakes), larger than magnitude 3.4. observed simultaneously at each bedrock location within 4 electric substation sites. Site amplifications at the bedrock location of 4 sites were compared among S wave, Coda wave energy, and background noise, and then compared to the previous results from the borehole location data. The site classification was also tried using resonancy frequency information at each site and location. The results suggested that all the electric substation sites showed similar site amplification patterns among S wave, Coda wave, and background noise. Each station showed its own characteristics of site amplification property in low, high and specific resonance frequency ranges. Comparison of this study to other results using different method can give us much more information about dynamic amplification of domestic sites characteristics and site classification.

Analysis of Site Amplification Characteristics of Several Seismic Stations Distributed in the Southern Korean Peninsula (국내 지진관측소 부지의 지반증폭특성 연구)

  • Kim, Jun-Kyoung
    • Tunnel and Underground Space
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    • v.16 no.6 s.65
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    • pp.486-494
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    • 2006
  • The horizontal to vertical (H/V) ratio technique in spectral domain is a common useful technique to estimate empirical site transfer function. The technique, originally proposed by Nakamura, is proposed to analyse the surface waves in the micrortremor records. The purpose of this paper is to estimate spectral ratio using observed data at the seismic stations distributed within Southern Korean Peninsula from the Fukuoka earthquake including 11 aftershocks. The results show that most of the stations have fairly good amplification characteristics in low frequency band. However, some of the seismic stations show one (resonant frequency specific to the site) or several local peaks of amplification factors with narrow high frequency band. Even though the site amplification characteristics are important information, we should be careful to analyse the observed ground motions from the seismic stations which have several very high amplification peaks for the deconvolution of seismic source and attenuation parameters.

Site characteristics and classification of seismic stations based on observed earthquake data (지진관측 자료를 이용한 국내 지진관측소의 지반특성 분류)

  • 박동희;연관희;장천중
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 2003.03a
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    • pp.61-68
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    • 2003
  • The H/V ratio (Horizontal to Vertical spectral ratio) has been used to infer site amplification without previous knowledge of near-surface geology and in fact may provide useful general site condition information. This method is used to classify the site characteristics of seismic stations in Korea by comparison with known H/V ratios representative of various sites all over the world. In addition, differences between horizontal and vertical kappa values were evaluated for each seismic stations by comparing WV ratio and Weak Motion amplification derived from inversion of stochastic ground motion parameters and were used as index to quantitatively classify the site characteristics.

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Case Study of Dynamic Amplification Characteristics of the Seismic Stations Using Observed Seismic Waves (관측지진파를 이용한 지반증폭특성 사례분석)

  • Lee, Jundae;Kim, Junkyoung
    • Journal of the Korean GEO-environmental Society
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    • v.10 no.1
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    • pp.35-41
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    • 2009
  • It is necessary to consider the site amplification for estimating SSI (soil structure interaction) and seismic source with more confidence. The horizontal to vertical (H/V) ratio technique in spectral domain is one of several techniques to estimate empirical site transfer function. The technique, originally proposed by Nakamura (1989), is applied to analyze the surface waves in the microtremor records. However, the application of this technique has been widened to the shear wave energy of strong motions for estimating site amplification. The purpose of this paper is to estimate spectral ratio using observed data at the seismic stations distributed within Southern Korean Peninsula from the Fukuoka earthquake including 11 aftershocks. The results show that each station has the its own characteristics of the specific resonance, high-band, and low-band frequency. The characteristics of the resonance frequency is more important because the quality of the seismic records are dependent on the resonance frequency. The result can be used for the study of site classification and removal of the site amplification effects from observed records can give us more reliable seismic source parameters.

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A Parametric Study on Site Amplification using Equivalent Linear Analysis (등가선형해석을 이용한 지반증폭 영향 요소 연구)

  • 김동수
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 2000.10a
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    • pp.98-107
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    • 2000
  • Free-field ground motion during earthquake is significantly affected by the local site conditions and it is essential for the seismic design to perform the ground response analysis In this study, ground response analyses based on the equivalent linear method were carried out to evaluate the effects of various ground conditions on the site amplification. Four major factors including the depth of the site(very soft and dense soil), the impedance ratio between soil layer and bed rock, linear analysis versus equivalent linear analysis, and the location of soft soil layer were deeply discussed. Based on the analysis results, the importance of various local site conditions on the site amplification was emphasized.

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Analysis of H/V Ratio using Recent Earthquake (국내관측소의 부지 증폭특성 연구)

  • Yoo, Seong-Hwa;Oh, Tae-Seok;Kim, Jun-Kyoung
    • 한국지구물리탐사학회:학술대회논문집
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    • 2006.06a
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    • pp.175-180
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    • 2006
  • The horizontal to vertical ratio technique in spectral domain is a common useful technique to estimate empircal site transfer function. The technique, originally proposed by Nakamura, is porposed to analyse the surface waves in the micortremor records. The purpose of this paper is to estimate spectral ratio using observed data at the seismic stations in Korean Peninsula from the Fukuoka earthquake including many aftershocks. The results show that most of the stations have fairly good amplification factors. However, some of the stations show that very high amplification factors at narrow high frequency band. Those stations which have very high amplification factors seem to do some kind of mechanical consideration for quality observation.

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