非因果滤波器在强震数据处理中的应用
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摘要
本文叙述了非因果滤波器的特点,以汶川主震记录为例,采用Butterworth非因果滤波器,研究了加零、余弦过渡以及截止频率对于强震动记录有关参数的影响,对比了四种非因果滤波器在不同阶数下的计算结果,探讨了滤波后的加速度保零和去零的问题。研究表明:借助于在记录的首尾加零得以实现的非因果滤波具有零相位特点,余弦过渡处理对于加零部分与原始记录间的过渡很必要;Butterworth非因果滤波器的计算结果比较稳定,PGV和PGD对于高通截止频率的选择比较敏感,当波纹系数为0.2dB时,宜使用Chebyshev I型非因果滤波器;当波纹系数为3dB时,宜使用Cheby-shev II型非因果滤波器;对于滤波后的加速度数据需要保零以适应数据间的协调。
The characteristics of the acausal filter for strong motion record processing are described.Taking Wenchuan mainshock records as examples,the Butterworth acausal filter is applied to analyze the influence of padding,cosine taper and corner frequency on the related ground motion parameters.Four kinds of the acausal filters with different orders are also deployed for the padding issues.The research shows that acausal filter could realize the zero phase character by zero padding and cosine taper between zeros part and the original records is necessary for data processing.The Butterworth acausal filter is much more stable among four kinds of filters,and PGV and PGD are sensible to the high-pass corner frequency.Chebyshev I acausal filter is available when ripple is 0.2 dB,while it is better to choose Chebyshev II acausal filter when ripple is 3 dB.The zero data of the filtered records should be kept to make the data compatible.
The characteristics of the acausal filter for strong motion record processing are described.Taking Wenchuan mainshock records as examples,the Butterworth acausal filter is applied to analyze the influence of padding,cosine taper and corner frequency on the related ground motion parameters.Four kinds of the acausal filters with different orders are also deployed for the padding issues.The research shows that acausal filter could realize the zero phase character by zero padding and cosine taper between zeros part and the original records is necessary for data processing.The Butterworth acausal filter is much more stable among four kinds of filters,and PGV and PGD are sensible to the high-pass corner frequency.Chebyshev I acausal filter is available when ripple is 0.2 dB,while it is better to choose Chebyshev II acausal filter when ripple is 3 dB.The zero data of the filtered records should be kept to make the data compatible.
引文
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[2]Converse A M,Brady A G.BAP:basic strong-motion accelerogram processing software,version 1.0[R].United States Department of the Interi-or Geological Survey,1992.
[3]Mollova G,Scherbaum F.Influence of parameters selection in Chebyshev filters on the strong motion data processing[J].Bulletin of EarthquakeEngineering,2007,5(4):609-627.
[4]Akkar S,Bommer J J.Influence of long-period filter cut-off on elastic spectral displacements[J].Earthquake Engineering and Structural Dy-namics,2006,35:1145-1165.
[5]Boore D M,Akkar S.Effect of causal and acausal filters on elastic and inelastic response spectra[J].Earthquake Engineering and Structural Dy-namics,2003,32:1729-1748.
[6]Bazzurro P,Sjoberg B,Luco N.Effects of strong motion processing procedures on time histories,elastic and inelastic spectra[C]//Invited work-shop on strong-motion record processing,California Strong-Motion Instrumentation Program Pacific Earthquake Engineering Research Center,2004:203-230.
[7]中国地震局.汶川8.0级地震未校正加速度记录[M].中国强震记录汇报,第十二集,第一卷,北京:地震出版社,2008.China Earthquake Administration.Wenchuan 8.0 earthquake uncorrected acceleration records[M].Report on strong motion records in China.Vol.12,No.1.Beijing:Earthquake Press,2008.(in Chinese)
[8]郑君里,杨为理.信号与系统[M].北京:高等教育出版社,2008.ZHENG Junli,YANG Weili.Signals and Systems[M].Beijing:Higher Education Press,2008.(in Chinese)
[9]Kanasewich E R.Time sequence analysis in geophysics[M].University of Alberta Press,1995.
[10]薛年喜.MATLAB在数字信号处理中的应用[M].北京:清华大学出版社,2003.XUE Nianxi.The application of MATLAB in the digital signal processing[M].Beijing:Tsinghua University Press,2003.(in Chinese)
[11]谢礼立,于双久.强震观测与分析原理[M].北京:地震出版社,1982.XIE Lili,YU Shuangjiu.Strong motion observation and analysis principle[M].Beijing:Earthquake Press,1982.(in Chinese)
[12]Boore D M,Bommer J J.Processing of strong-motion accelerograms:needs,options and consequences[J].Soil Dynamics and Earthquake En-gineering,2005,25:93-115.
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