基于弹性位移解析解的相位谱改进对随机合成法工程应用的影响
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摘要
介绍了一种对随机合成法中子源地震动相位谱改进的方案,强调一个点源引起地震动的相位谱应该与地壳速度结构、介质参数,尤其是场地与源点的几何关系密切相关,努力在随机合成中减少随机性。即,将无限均匀介质中剪切位错源引起的位移解所对应的加速度傅式谱的相位谱,与所估计的幅值谱结合,形成复谱,再通过傅立叶逆变换生成加速度时程。通过与传统随机合成法的对比认为:在震源-传播途径-场地条件一体化的强地震动估计方法中,采用基于弹性位移解析解的相位谱,可以有效地减小或消除随机数对平均震源模型选定及合成地震动场的干扰。
A new improvement on phase spectrum in stochastic synthesis technique was introduced.The main idea of the improvement is considering the property of propagation medium and the source-site geometry into phase spectrum.In the improvement,the analytical solution of elastic displacement response to a shear dislocation source in infinite homogeneous space was first calculated.The acceleration of the obtained displacement time history was computed and then transformed into frequency domain to extract the phase spectrum.The extracted phase spectrum was then combined with an amplitude spectrum founded based on ω2 source spectrum to form a complex spectrum from which the final ground acceleration time history was established by using inverse FFT transform.Both conventional stochastic synthesis method and the improved stochastic synthesis were applied to a ground motion simulation scenario,and the comparison of simulation results shows that the improvement reduced the distortion of random number on the selection of mean source model and the simulated ground motion field.
A new improvement on phase spectrum in stochastic synthesis technique was introduced.The main idea of the improvement is considering the property of propagation medium and the source-site geometry into phase spectrum.In the improvement,the analytical solution of elastic displacement response to a shear dislocation source in infinite homogeneous space was first calculated.The acceleration of the obtained displacement time history was computed and then transformed into frequency domain to extract the phase spectrum.The extracted phase spectrum was then combined with an amplitude spectrum founded based on ω2 source spectrum to form a complex spectrum from which the final ground acceleration time history was established by using inverse FFT transform.Both conventional stochastic synthesis method and the improved stochastic synthesis were applied to a ground motion simulation scenario,and the comparison of simulation results shows that the improvement reduced the distortion of random number on the selection of mean source model and the simulated ground motion field.
引文
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[2]Boore D M.Simulation of ground motion using the stochasticmethod[J].Pure and Applied Geophysics,2003,160:635-676
[3]Beresnev I A,Atkinson G M.Stochastic finite-fault modelingof ground motions from the 1994 Northridge,California,earthquake,I.Validation on rock sites[J].Bulletin of theSeismological Society of America,1998,88(6):1392-1401
[4]Tao X X,Anderson J G.Near field strong ground motionsimulation[C]//Proceedings of the InternationalConference on Advances and New Challenges in EarthquakeEngineering Research.Harbin,2002:79-86
[5]Motazedian D,Atkinson G M.Stochastic finite-fault modelingbased on a dynamic corner frequency[J].Bulletin of theSeismological Society of America,1998,95(3):995-1010
[6]孙晓丹.强地震动场估计中若干问题的研究[D].哈尔滨:哈尔滨工业大学,2010(Sun Xiaodan.Some issues onestimation of strong ground motion field[D].Harbin:Harbin Institute of Technology,2010(in Chinese))
[7]Aki K,Richards P G.Quantitative seismology[M].2ndedition.CA:University Science Books,2002
[8]Sun X D,Tao X X,Tang A P,et al.Hybrid slip model fornear-field ground motion prediction based on uncertainty ofsource parameters[J].Transaction of Tianjin University,2010,16(1):61-67
[9]Boore D M,Joyner W B.Site amplifications for genericrock sites[J].Bulletin of the Seismological Society ofAmerica,1997,87:327-34
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