地震动随场地深度变化的相干性分析
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摘要
目前有关地震动相干性研究基本上是限于自由场地的地面运动相干性问题。为探究地震动随场地深度变化的相干性,寻求一种适用于不同类型场地随深度变化的地震动相干函数模型,以日本KiK-net台网采集的2 679对地震动记录为基础,利用随机振动理论和数字信号处理技术对不同类型场地随深度变化的地震动相干性问题进行了研究。通过对水平向地震动分量相干函数计算值的拟合,建立了一种适用于不同类型场地的水平向地震动随深度变化的相干函数模型,并进行了参数回归分析。分析结果表明:震级及震中距(<200 km)对相干函数的影响可忽略不计;剪切波速对相干函数产生较大的影响,与浅层土相比,深层土剪切波速的影响更大;水平向地震动的相干函数值随深度和频率的增大呈指数形式衰减;相较于深度的影响,频率对相干函数值衰减速率的影响更加明显。在对地震动相干函数值的估计中,场地条件是不容忽视的因素,随着场地由硬变软,相干函数值随深度的衰减愈来愈快。
At present, the study on coherence of ground motions is limited to the coherence of ground motions at free sites. Here, in order to investigate the coherence of ground motions with variation of site depth and seek a ground motions coherence function model with depth variation of different types of sites, based on 2 679 pairs of ground motion records collected in KiK-net of Japan, problems about ground motion coherence with depth variation of different types of sites were studied using the random vibration theory and the digital signal processing technique. Through fitting calculated values of the coherence function of ground motions' horizontal components, a coherence function model applicable for ground motions' horizontal components with depth variation of different types of sites was established and the parametric regression analysis was done for this model. The results showed that effects of earthquake magnitude and epicentral distance(less than 200 km) on the coherence function can be neglected; shear wave velocity(VS) affects the coherence function more largely; compared with shallow soil's Vs, effects of deep soil's Vs are larger; with increase in depth and frequency, the coherence function of ground motions' horizontal components reveals an exponential decay trend; compared with effects of depth, effects of frequency on the coherence function's decay rate are more obviously; in estimating the coherence function of ground motions, site condition is a factor which can't be ignored; the softer the site, the faster the decay of the coherence function values with variation of depth.
At present, the study on coherence of ground motions is limited to the coherence of ground motions at free sites. Here, in order to investigate the coherence of ground motions with variation of site depth and seek a ground motions coherence function model with depth variation of different types of sites, based on 2 679 pairs of ground motion records collected in KiK-net of Japan, problems about ground motion coherence with depth variation of different types of sites were studied using the random vibration theory and the digital signal processing technique. Through fitting calculated values of the coherence function of ground motions' horizontal components, a coherence function model applicable for ground motions' horizontal components with depth variation of different types of sites was established and the parametric regression analysis was done for this model. The results showed that effects of earthquake magnitude and epicentral distance(less than 200 km) on the coherence function can be neglected; shear wave velocity(VS) affects the coherence function more largely; compared with shallow soil's Vs, effects of deep soil's Vs are larger; with increase in depth and frequency, the coherence function of ground motions' horizontal components reveals an exponential decay trend; compared with effects of depth, effects of frequency on the coherence function's decay rate are more obviously; in estimating the coherence function of ground motions, site condition is a factor which can't be ignored; the softer the site, the faster the decay of the coherence function values with variation of depth.
引文
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[3] 阿布都瓦里斯,俞瑞芳,俞言祥.基于汶川地震加速度记录的地震动相干函数变化特性[J].振动与冲击,2013,32(16):70-75.ABUDUWALISI,YU Ruifang,YU Yanxiang.Spatial variation of ground motions based on wenchuan acceleration records[J].Journal of Vibration and Shock,2013,32(16):70-75.
[4] 陈清军,杨永胜,王沿朝.基于强震台阵记录的地震动空间相干函数实用模型[J].土木工程学报,2016(增刊1):1-6.CHEN Qingjun,YANG Yongsheng,WANG Yanchao.A practical spatial coherence model of seismic ground motion based on strong earthquake array records[J].China Civil Engineering Journal,2016(Sup1):1-6.
[5] DULINSKA JM.Importance of ground motion spatial variability effects on earth dam[J].International Journal of Earth Sciences and Engineering,2012,5(1):1-9.
[6] BI K,HAO H.Numerical simulation of pounding damage to bridge structures under spatially varying ground motion[J].Engineering Structures,2013,46:62-76.
[7] JEREMIC B,TAFAZZOLI N,ANCHETA T,et al.Seismic behavior of NPP structures subjected to realistic 3D,inclined seismic ground motions,in variable layered soil/rock,on surface of embedded foundations[J].Nuclear Engineering and Design,2013,265:85-94.
[8] 王国新,王招招,王东明.随深度变化的地震动相干性研究[J].振动与冲击,2013,32(17):118-122.WANG Guoxin,WANG Zhaozhao,WANG Dongming.Coherence variations of different strong ground motion arrays with depth[J].Journal of Vibration and Shock,2013,32(17):118-122.
[9] 胡灿阳,陈清军.基于EMD和最小二乘法的基线飘移研究[J].振动与冲击,2010,29(3):162-167.HU Canyang,CHEN Qingjun.Research on baseline drift using least square and EMD[J].Journal of Vibration and Shock,2010,29(3):162-167.
[10] EPRI.Program on technology innovation:effects of spatial incoherence on seismic ground motions[R].Technical Report 1015110,EPRI,Palo Alto,CA:2007.
[11] SVAY A,PERRON V,IMTIAZ A.Spatial coherency analysis of seismic ground motions from a rock site dense array implemented during the Kefalonia 2014 aftershock sequence[J].Earthquake Engineering & Structural Dynamics,2017,46:1895-1917.
[12] ABRAHAMSON N,SCHNEIDER J F,STEPP J C.Empirical spatial coherency functions for application to soil-structure interaction analyses[J].Earthquake Spectra,1991,7(1):1-27.
[13] ZERVA A.Spatial variation of seismic ground motions,modelling and engineering application[M].Boca Raton:CRC Press,2009.
[14] TODOROVSKA M I,TRIFUNAC M D,DING H P.Coherency of dispersed synthetic earthquake ground motion at small separation distances:dependence on site conditions[J].Soil Dynamics and Earthquake Engineering,2015,79:253-264.
[15] DING H P,TRIFUNAC M D,TODOROVSKA M I.Coherence of dispersed synthetic strong earthquake ground motion at small separation distances[J].Soil Dynamics and Earthquake Engineering,2015,70:1-10.