基于汶川M_S8.0地震强震动记录的山体地形效应分析
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摘要
2008年汶川MS8.0地震中,固定和流动地形影响台阵记录到大量主余震记录,本文通过对其均方根加速度、相对持时、频谱等要素进行分析,讨论了山体地形效应的特征及其影响因素.对于自贡西山公园地形台阵各测点的分析结果显示:该台阵山脚基岩位置地震动的均方根加速度和相对持时明显低于山体周边土层场地和山体基岩测点;随着高程的增加,山体基岩测点的均方根加速度逐渐变大,相对持时则变化不大,傅里叶谱形状也大体一致,在2.0—5.0Hz频段内有所放大;山体周边土层场地和山体地形对于相同地震动输入中不同频段内地震动能量的放大水平不同,从而导致二者的地表地震动强度产生显著差异,且前者对地震动持时的增加更加显著.
It is important for the large-scale engineering seismic fortification in the mountain area to analyze the hill topography effect of the strong ground motion based on the earthquake records.In 2008 Wenchuan MS8.0earthquake,a lot of strong ground motion data were recorded by fixed and mobile observation arrays.By analyzing the root-mean-square(RMS)acceleration,this paper discusses 90% duration and spectrum characteristics,the hill topography effect characteristics and its influencing factors.As to the Xishan park topography array in Zigong city,with the altitude increasing,the RMS acceleration becomes larger,however,the 90% duration does not change obviously;the shape of the Fourier spectra is similar except the amplitude in the frequency bandwidth 2.0—5.0Hz is amplified to some extent;the ground motion energy is amplified differently in the different frequency bandwidth by the soil site around the hill and the hill topography,which makes the ground motion different;the soil site around the hill makes the ground motion duration last longer compared with the hill.
It is important for the large-scale engineering seismic fortification in the mountain area to analyze the hill topography effect of the strong ground motion based on the earthquake records.In 2008 Wenchuan MS8.0earthquake,a lot of strong ground motion data were recorded by fixed and mobile observation arrays.By analyzing the root-mean-square(RMS)acceleration,this paper discusses 90% duration and spectrum characteristics,the hill topography effect characteristics and its influencing factors.As to the Xishan park topography array in Zigong city,with the altitude increasing,the RMS acceleration becomes larger,however,the 90% duration does not change obviously;the shape of the Fourier spectra is similar except the amplitude in the frequency bandwidth 2.0—5.0Hz is amplified to some extent;the ground motion energy is amplified differently in the different frequency bandwidth by the soil site around the hill and the hill topography,which makes the ground motion different;the soil site around the hill makes the ground motion duration last longer compared with the hill.
引文
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Hartzell S H,Carver D L,King K W.1994.Initial investigation of site and topographic effects at Robinwood Ridge,California[J].Bull Seismol Soc Am,84(5):1336--1349.
Husid R L.1969.Analisis de terremotos:Analisis general[J].Revista del IDIEM,8(1):21--42.
Paolucci R.2002.Amplification of earthquake ground motion by steep topographic irregularities[J].Earthquake EngngStruct Dyn,31(10):1831--1853.
Spudich P,Hellweg M,Lee W H K.1996.Directional topographic site response at Tarzana observed in aftershocks ofthe 1994 Northridge,California,earthquake:Implications for mainshock motions[J].Bull Seismol Soc Am,86(1B):S193--S208.
Tucker B E,King J L,Hatzfeld D,Nersesov I L.1984.Observations of hard-rock site effects[J].Bull Seismol Soc Am,74(1):121--136.
孙崇绍,闵祥仪,周民都.2011.陇南山区局部地形对地震动强度的影响[J].西北地震学报,33(4):331--335.Sun C S,Min X Y,Zhou M D.2011.Influence of local topography on ground motion in mountain region of southernGansu Province[J].Northwestern Seismological Journal,33(4):331--335(in Chinese).
唐晖,李小军,李亚琦.2012.自贡西山公园山脊地形场地效应分析[J].振动与冲击,31(8):74--79.Tang H,Li X J,Li Y Q.2012.Site effect of topography on ground motions of Xishan park of Zigong city[J].Journal ofVibration and Shock,31(8):74--79(in Chinese).
王海云,谢礼立.2010.自贡市西山公园地形对地震动的影响[J].地球物理学报,53(7):1631--1638.Wang H Y,Xie L L.2010.Effects of topography on ground motion in the Xishan park,Zigong city[J].Chinese Journalof Geophysics,53(7):1631--1638(in Chinese).
杨宇,李小军,贺秋梅.2011.自贡西山公园山脊场地地形和土层效应数值模拟[J].震灾防御技术,6(4):436--447.Yang Y,Li X J,He Q M.2011.Numerical simulation for site effect of ridge terrain and overlaying soil in Zigong XishanPark[J].Technology for Earthquake Disaster Prevention,6(4):436--447(in Chinese).
Boore D M.1972.A note on the effect of simple topography on seismic SH waves[J].Bull Seismol Soc Am,62(1):275--284.
Davis L L,West L R.1973.Observed effects of topography on ground motion[J].Bull Seismol Soc Am,63(1):283--298.
Hanks T C.1979.bvalues and seismic source models:Implications for tectonic stress variations along active crustal faultzones and the estimation of high-frequency strong ground motion[J].J Geophys Res,84(B5):2235--2242.
Hartzell S H,Carver D L,King K W.1994.Initial investigation of site and topographic effects at Robinwood Ridge,California[J].Bull Seismol Soc Am,84(5):1336--1349.
Husid R L.1969.Analisis de terremotos:Analisis general[J].Revista del IDIEM,8(1):21--42.
Paolucci R.2002.Amplification of earthquake ground motion by steep topographic irregularities[J].Earthquake EngngStruct Dyn,31(10):1831--1853.
Spudich P,Hellweg M,Lee W H K.1996.Directional topographic site response at Tarzana observed in aftershocks ofthe 1994 Northridge,California,earthquake:Implications for mainshock motions[J].Bull Seismol Soc Am,86(1B):S193--S208.
Tucker B E,King J L,Hatzfeld D,Nersesov I L.1984.Observations of hard-rock site effects[J].Bull Seismol Soc Am,74(1):121--136.
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