地震动峰值放大与盆地深度关系的初步数值模拟
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摘要
沉积盆地对"超高、超大、超长"结构的地震动特性有显著的影响,认识盆地效应机理、刻画盆地放大特性是震害防御工作中亟待解决的问题。简要回顾了几次大地震中出现的典型盆地效应特性及其出现的原因,对前人提出的产生盆地效应的物理机制作了简要的总结,最后利用解耦的近场波动数值模拟方法,对SH波垂直入射情况下的二维理想盆地模型的水平方向地震动峰值放大倍数与盆地深度的关系,进行了初步的数值模拟研究,计算结果发现:(1)总体上,盆地地表放大系数与盆地深度有很好的相关性(近乎是线性关系),表现为随盆地深度的增加,盆地的放大效应也逐渐增大;(2)对于形状对称的理想盆地模型,在盆地中央附近出现了异常的放大,表现出典型的"盆地聚焦效应";(3)对于形状不对称的理想盆地模型,在盆地边缘和中央均出现异常的放大,表现出显著的"盆地边缘效应"和"中心聚焦效应"。
Sedimentary basin has a significant impact on the earthquake ground motion characteristics of the ‘Super High,Super Big,Super Long'structures. Studying the physical mechanism of the basin effect and the characteristics of the basin amplification is an urgent problem in the work of preventing the earthquake damage. In this article,we first briefly review the typical basin effect and the course in a few representative earthquakes,and summary the possibly physical mechanism of these phenomena predecessors have proposed. Then the decoupled method of numerical simulating wave propagation of near field is applied to study the dependence of the amplification of horizontally peak ground motion on the basin depth subjected to the vertically incident plain SH wave. We conduct the preliminary numerical simulating study and the results indicate( 1) that on the whole the basin effect has a good relation with the basin depth( almost linear relation),that with the basin deepening,the basin amplification factor getting bigger;( 2) that symmetric basin may occur the typical ‘focusing effect'easily and the abnormally big amplification factor appear around the deepest depth of the basin;( 3) that asymmetric basin may perform the ‘basin-edge'effect and the ‘focusing effect'simultaneously,with the abnormal amplification factor occur in two locations.
Sedimentary basin has a significant impact on the earthquake ground motion characteristics of the ‘Super High,Super Big,Super Long'structures. Studying the physical mechanism of the basin effect and the characteristics of the basin amplification is an urgent problem in the work of preventing the earthquake damage. In this article,we first briefly review the typical basin effect and the course in a few representative earthquakes,and summary the possibly physical mechanism of these phenomena predecessors have proposed. Then the decoupled method of numerical simulating wave propagation of near field is applied to study the dependence of the amplification of horizontally peak ground motion on the basin depth subjected to the vertically incident plain SH wave. We conduct the preliminary numerical simulating study and the results indicate( 1) that on the whole the basin effect has a good relation with the basin depth( almost linear relation),that with the basin deepening,the basin amplification factor getting bigger;( 2) that symmetric basin may occur the typical ‘focusing effect'easily and the abnormally big amplification factor appear around the deepest depth of the basin;( 3) that asymmetric basin may perform the ‘basin-edge'effect and the ‘focusing effect'simultaneously,with the abnormal amplification factor occur in two locations.
引文
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[10]王海云.渭河盆地中土层场地对地震动的放大作用[J].地球物理学报,2011,54(1):137-150,WANG Haiyun.Amplification effects of soil sites on ground motion in the Weihe basin[J].Chinese Journal of Geophysics,2011,54(1):137-150.(in Chinese)
[11]J.P.Stewart,Y.Choi and R.W.Graves.(2005).“Empirical Characterization of Site Conditions on Strong Ground Motion”Report to Pacific Earthquake Engineering Research Center.
[12]李雪强.沉积盆地地震效应研究[D].哈尔滨:中国地震局工程力学研究所.2011.LI Xueqiang.Study on seismic effect of sedimentary basin[D].Harbin:Institute of Engineering Mechanics,China Earthquake Administration,2011.(in Chinese)
[13]廖振鹏.近场波动的数值模拟[J].力学进展,1997,27(2):193-212.LIAO Zhenpeng.Numerical simulation of near-field wave motion[J].Advances in Mechanics,1997,27(2):193-212.(in Chinese)
[14]廖振鹏.工程波动理论导引[M].北京:科学出版社,1996.LIAO Zhenpeng.Introduce to the wave motion theories in engineering[M].Beijing:Science Press.1996.(in Chinese)
[15]陈学良.挡土墙地震反应的波动模拟分析[D].哈尔滨:中国地震局工程力学研究所.2001.CHEN Xueliang.Analysis of the seismic response of retaining wall in the wave propagation simulation[D].Harbin:Institute of Engineering Mechanics,China Earthquake Administration,2001.(in Chinese)
[2]Kawase H and K.Aki.A study on the response of a soft basin for incident S,P,and Rayleigh waves with special reference to the long duration observed in Mexico City[J].Bulletin of the Seismological Society of America,1989,79(5):1361-1382.
[3]Graves R W,A.Pitarka and P.G.Somerville.Ground-motion amplification in the Santa Monica area:Effects of shallow basin-edge structure[J].Bulletin of the Seismological Society of America,1998,88(5):1224-1242.
[4]Alex,C.M and K.B.Olsen(1998).Lens-effect in Santa Monica?,Getphys.Res.Lett.Submitted.
[5]Gao.S,H.Liu,P.M.Davis and L.Knopoff(1996).Localized amplification of seismic waves and correlation with damage due to the Northridge earthquake:evidence for focusing in Santa Monica,Bull Seism Soc Am.86,S209-S230.
[6]Kawase H.The cause of the damage belt in Kobe:"the basin-edge effect,"constructive interference of the direct S wave with the basin induced diffracted/Rayleigh-waves[J].Seismological Research Letters,1996,67(5):25-34.
[7]S.J.Lee,D.Komatitsch,B.S.Huang and J.Tromp(2009).Effects of Topography on Seismic-Wave Propagation:An Example from Northern Taiwan.Bulletin of the Seismological Society of America,Vol.99,No.1,pp.314–325,February 2009.
[8]郭恩,周锡元.汶川地震盆地效应的思考与建议[J].防灾减灾工程学报,2010(4):459-465.GUO En,ZHOUXiyuan.Study on basin effects of Wenchuan earthquake[J].Journal of Disaster Prevention and Mitigation Engineering,2010(4):459-465.(in Chinese).
[9]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).BO Jingshan,QI Wenhao,LIU Hongshuai,et al.Abnormality of seismic intensity in Hanyuan during Wenchuan earthquake,2009,29(6).(in Chinese)
[10]王海云.渭河盆地中土层场地对地震动的放大作用[J].地球物理学报,2011,54(1):137-150,WANG Haiyun.Amplification effects of soil sites on ground motion in the Weihe basin[J].Chinese Journal of Geophysics,2011,54(1):137-150.(in Chinese)
[11]J.P.Stewart,Y.Choi and R.W.Graves.(2005).“Empirical Characterization of Site Conditions on Strong Ground Motion”Report to Pacific Earthquake Engineering Research Center.
[12]李雪强.沉积盆地地震效应研究[D].哈尔滨:中国地震局工程力学研究所.2011.LI Xueqiang.Study on seismic effect of sedimentary basin[D].Harbin:Institute of Engineering Mechanics,China Earthquake Administration,2011.(in Chinese)
[13]廖振鹏.近场波动的数值模拟[J].力学进展,1997,27(2):193-212.LIAO Zhenpeng.Numerical simulation of near-field wave motion[J].Advances in Mechanics,1997,27(2):193-212.(in Chinese)
[14]廖振鹏.工程波动理论导引[M].北京:科学出版社,1996.LIAO Zhenpeng.Introduce to the wave motion theories in engineering[M].Beijing:Science Press.1996.(in Chinese)
[15]陈学良.挡土墙地震反应的波动模拟分析[D].哈尔滨:中国地震局工程力学研究所.2001.CHEN Xueliang.Analysis of the seismic response of retaining wall in the wave propagation simulation[D].Harbin:Institute of Engineering Mechanics,China Earthquake Administration,2001.(in Chinese)
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