基于地脉动谱比法的场地特征参数快速测定
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摘要
通过37个场地的地脉动单点三分量观测,研究了地脉动单点谱比卓越频率与场地覆盖层厚度、不同深度等效剪切波速以及特征周期等场地特征参数之间的相关性;通过不同区域相关关系以及地震动谱比研究结果的对比,探讨了利用地脉动单点谱比法快速测定场地特征参数的可行性和精度。结果表明:地脉动H/V谱比卓越周期与场地覆盖层厚度存在明显相关性,利用地脉动单点谱比法快速测定场地覆盖层厚度,在1~2 Hz频带区间内不同地区相对误差小于15%,在这一区间外相对误差有所增大;地脉动H/V谱比卓越周期与覆盖层等效特征周期T_s大体一致;地脉动H/V谱比卓越周期大于0.5 s时,场地的等效剪切波速V_(s20)和V_(s30)以及等效周期T_(s20)和T_(s30)变化不大,平均分别为200 m/s,250m/s,0.8 s和0.6 s。
Micro-tremors at 37 sites were observed and measured.Correlations among the micro-tremor H/V spectra predominant frequency and site characteristic parameters including thickness of sediment,equivalent shear wave velocities in different depths,and site period were studied.Comparing these correlations and the study results of ground motion H/V spectra in different regions,the feasibility and accuracy of using the micro-tremor H/V spectra method to quickly measure site characteristic parameters were explored.Results showed that the predominant frequency of microtremor H/V has a strong correlation with the thickness of sediment,if using the micro-tremor H/V spectra method to measure thicknesses of sediment in different regions,their relative differences within a frequency range of 1—2 Hz are less than 15%,the relative differences increase beyond this frequency range; the predominant period of the micro-tremor H/V spectra is almost the same as the site sediment equivalent period; when the micro-tremor H/V spectra's predominant period > 0.5 s,the site's equivalent shear wave velocities V_(s20) and V_(s30) as well as equivalent periods T_(s20) and T_(s30) have little changes,they have average values of 200 m/s,250 m/s,0.8 s and 0.6 s,respectively.
Micro-tremors at 37 sites were observed and measured.Correlations among the micro-tremor H/V spectra predominant frequency and site characteristic parameters including thickness of sediment,equivalent shear wave velocities in different depths,and site period were studied.Comparing these correlations and the study results of ground motion H/V spectra in different regions,the feasibility and accuracy of using the micro-tremor H/V spectra method to quickly measure site characteristic parameters were explored.Results showed that the predominant frequency of microtremor H/V has a strong correlation with the thickness of sediment,if using the micro-tremor H/V spectra method to measure thicknesses of sediment in different regions,their relative differences within a frequency range of 1—2 Hz are less than 15%,the relative differences increase beyond this frequency range; the predominant period of the micro-tremor H/V spectra is almost the same as the site sediment equivalent period; when the micro-tremor H/V spectra's predominant period > 0.5 s,the site's equivalent shear wave velocities V_(s20) and V_(s30) as well as equivalent periods T_(s20) and T_(s30) have little changes,they have average values of 200 m/s,250 m/s,0.8 s and 0.6 s,respectively.
引文
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[2]CHIOU S J B,YOUNGS R R.An NGA model for the average horizontal component of peak ground motion and response spectra[J].Earthquake Spectra,2008,24(1):173-215.
[3]ZHAO J X,XU H.A comparison of VS30 and site period as site-effect parameters in response spectral ground-motion prediction equations[J].Bulletin of the Seismological Society of America,2013,103(1):1-18.
[4]HASSANI B,ATKINSON G M.Applicability of the site fundamental frequency as a VS30 proxy for Central and Eastern North America[J].Bulletin of the Seismological Society of America,2016,106(2):653-664.
[5]FIELD E,CLEMENT A,JACOB K,et al.Earthquake siteresponse study in Giumri(Formerly Leninakan),Armenia,using ambient noise observations[J].Bulletin of the Seismological Society of America,1995,85(1):349-353.
[6]LERMO J,CHáVEZGARCíA F J.Are microtremors useful in site response evaluation?[J].Bulletin of the Seismological Society of America,1994,84(5):1350-1364.
[7]NAKAMURA Y.A method for dynamic characteristics of subsurface using microtremors on the ground surface[R].Railway Technical Research Institute Quarterly Reports,1989.
[8]SEHT I V,WOHLENBERG J.Microtremor measurements used to map thickness of soft sediments[J].Bulletin of the Seismological Society of America,1999,89(1):250-259.
[9]PAROLAI S.New relationships between vs,thickness of sediments,and resonance frequency calculated by the H/V ratio of seismic noise for the Cologne Area(Germany)[J].Bulletin of the Seismological Society of America,2002,92(6):2521-2527.
[10]曾立峰.地脉动在黄土地区厚覆盖层探测中的应用研究[D].兰州:中国地震局兰州地震研究所,2012.
[11]BROWN C J,VOYTEK E B,LANE J W,et al.Mapping bedrock surface contours using the horizontal-to-vertical spectral ratio(HVSR)method near the middle quarter srea,Woodbury,Connecticut[R].Center for Integrated Data Analytics Wisconsin Science Center,2013.
[12]NAKAMURA Y.Clear identification of fundamental idea of Nakamura's technique and its applications[C]//Proceedings of 12th World Conference on Earthquake Engineering.Auckland,2000.
[13]哈尔滨市轨道交通一期工程场地地震安全性评价报告[R].中国地震局工程力学研究所,2003.
[14]CATELLO A,AGUACIL G,ANASTASIADIS,A,et al.Guidelines for the implementation of the H/V spectral ratio technique on ambient vibrations measurements,processing and interpretation[R].SESAME European Research Project WP12,2004.