运用广义反演法研究汶川地震场地效应
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摘要
选取从96个汶川地震余震中由28个强震动台站获取的602组强震动记录,假设地表观测到的地震动由震源、路径和场地三项因素组成,运用广义反演法(GIT)分离这三项因素,获得这些台站的场地反应,并与采用HVSR法获得的结果进行比较。结果表明:两种方法获得的场地卓越频率具有较好的一致性,但是对于1.0～5.0Hz、5.0～10.0Hz和1.0～10.0Hz频段内的平均场地放大,HVSR法获得的结果要普遍小于广义反演法。进一步说明了HVSR方法可以合理精确地估计场地的卓越频率但却低估平均场地放大。最后统计这三个频段内的平均场地放大与台站上覆土层20m的平均剪切波速(V s20)间的函数关系,结果表明两者之间存在较强的相关性。
Total 602 recordings from 28 strong motion stations captured in 96 aftershocks of the Wenchuan Earthquake were selected and processed at first.It was assumed that the observed surface ground motion is comprised of three factors that are the source,path and site.The generalized inversion technique(GIT) was applied to separate these factors and then the site responses of these stations were obtained.Comparing them with the ones by the HVSR method,it shows that the site predominant frequency from two methods have a good agreement,but for the average site amplification in the frequency bands of 1.0-5.0Hz,5.0-10.0Hz and 1.0-10.0Hz,the results by HVSR method are mostly smaller than the ones by GIT.It further illustrates that the HVSR method can accurately evaluate the site predominant frequency but underestimate the site amplification amplitude.At last the relationship between the average site amplification of those three frequency bands and the average uppermost-20m shear wave velocity(V s20) was regressed.It shows that there is a strong correlation between them.
Total 602 recordings from 28 strong motion stations captured in 96 aftershocks of the Wenchuan Earthquake were selected and processed at first.It was assumed that the observed surface ground motion is comprised of three factors that are the source,path and site.The generalized inversion technique(GIT) was applied to separate these factors and then the site responses of these stations were obtained.Comparing them with the ones by the HVSR method,it shows that the site predominant frequency from two methods have a good agreement,but for the average site amplification in the frequency bands of 1.0-5.0Hz,5.0-10.0Hz and 1.0-10.0Hz,the results by HVSR method are mostly smaller than the ones by GIT.It further illustrates that the HVSR method can accurately evaluate the site predominant frequency but underestimate the site amplification amplitude.At last the relationship between the average site amplification of those three frequency bands and the average uppermost-20m shear wave velocity(V s20) was regressed.It shows that there is a strong correlation between them.
引文
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[14]McCann M W J,Shah H C.Determining strong motionduration of earthquakes[J].Bulletin of the SeismologicalSociety of America,1979,69(4):1253-1265
[15]Castro R R,Pacor F,Bindi D,et al.Site response ofstrong motion stations in the Umbria,Central Italy,Region[J].Bulletin of the Seismological Society of America,2004,94(2):576-590
[16]Salazar W,Sardina V,Cortina J D.A hybrid inversiontechnique for the evaluation of source,path,and siteeffects employing S-wave spectra for subduction and upper-crustal earthquakes in El Salvador[J].Bulletin of theSeismological Society of America,2007,97(1B):208-221
[17]Hassani B,Zafarani H,Farjoodi J,et al.Estimation ofsite amplification,attenuation and source spectra of S-waves in the East-Central Iran[J].Soil Dynamics andEarthquake Engineering,2011,31(10):1397-1413
[2]Wang D,Xie L L.Study on response spectral accelerationfrom the great Wenchuan,China Earthquake of May 12,2008[J].Journal of Earthquake Engineering,2010,14(6):934-952
[3]Wen R Z,Ren Y F,Zhou Z H,et al.Preliminary siteclassification of free-field strong motion stations based onWenchuan earthquake records[J].Earthquake Science,2010,23(1):101-110
[4]Wen R Z,Ren Y F,Shi D C.Improved HVSR siteclassification method for free-field strong motion stationsvalidated with Wenchuan aftershock recordings[J].Earthquake Engineering and Engineering Vibration,2011,10(3):325-337
[5]薄景山,齐文浩,刘红帅,等.汶川特大地震汉源烈度异常原因的初步分析[J].地震工程与工程振动,2009,29(6):53-63(Bo Jingshan,Qi Wenhao,Liu Hongshuai,etal.Abnormality of seismic intensity in Hanyuan duringWenchuan earthquake[J].Journal of EarthquakeEngineering and Engineering Vibration,2009,29(6):53-63(in Chinese))
[6]Borcherdt R D.Effects of local geology on ground motionnear San Francisco bay[J].Bulletin of the SeismologicalSociety of America,1970,60(1):29-61
[7]Andrews D J.Objective determination of source parametersand similarity of earthquakes of different size[J].Geophysical Monograph Series,1986,37:259-267
[8]欧阳行艳,章文波.利用强震记录进行场地反应分析研究综述[J].世界地震工程,2008,24(3):118-126(Ouyang Xingyan,Zhang Wenbo.Review on analysis ofsite effect by strong motion data[J].World EarthquakeEngineering,2008,24(3):118-126(in Chinese))
[9]Iwata T,Irikura K.Separation of source,propagation andsite effects from observed S-wave[J].Journal of theSeismological Society of Japan,1986,39(2):579-593
[10]Iwata T,Irikura K.Source parameters of the 1983 JapanSea earthquake sequence[J].Journal of Physics of theEarth,1988,36(4):155-184
[11]章文波,谢礼立,郭明珠.利用强震记录分析场地的地震反应[J].地震学报,2001,23(6):604-614(ZhangWenbo,Xie Lili,Guo Mingzhu.Estimation on site-amplification from different methods using strong motiondata obtained in Tangshan,China[J].Acta SeismologicaSinica,2001,23(6):604-614(in Chinese))
[12]李小军.汶川8.0级地震余震固定台站观测未校正加速度记录[M].北京:地震出版社,2009
[13]Husid R.Gravity effects on the earthquake response ofyielding structures[D].California of America:CaliforniaInstitute of Technology,1967
[14]McCann M W J,Shah H C.Determining strong motionduration of earthquakes[J].Bulletin of the SeismologicalSociety of America,1979,69(4):1253-1265
[15]Castro R R,Pacor F,Bindi D,et al.Site response ofstrong motion stations in the Umbria,Central Italy,Region[J].Bulletin of the Seismological Society of America,2004,94(2):576-590
[16]Salazar W,Sardina V,Cortina J D.A hybrid inversiontechnique for the evaluation of source,path,and siteeffects employing S-wave spectra for subduction and upper-crustal earthquakes in El Salvador[J].Bulletin of theSeismological Society of America,2007,97(1B):208-221
[17]Hassani B,Zafarani H,Farjoodi J,et al.Estimation ofsite amplification,attenuation and source spectra of S-waves in the East-Central Iran[J].Soil Dynamics andEarthquake Engineering,2011,31(10):1397-1413
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