基于谐小波变换的地震波非平稳随机模型建立

Establishment of nonstationary stochastic model of earthquake record using harmonic wavelet transforms

利用谐小波变换对实际强震记录的时变谱进行估计,并统计分析了与抗震规范相容的3类不同场地上地震波的时变谱特征,分析发现对于较硬场地上的地震波在时域内平稳段较短,下降段衰减较快,而在频域内具有较大的中心频率和较宽的频带;利用均匀调制非平稳随机模型模拟地震波的时变谱,把非线性函数的参数识别问题转化成求解无约束优化问题,利用拟牛顿迭代法求最优解,得到3类不同场地上地震波的均匀调制非平稳随机模型中各谱参数和时间包络中各参数的具体数值,为了定量地确定模拟模型的精度,定义了误差函数,验证了所提时变谱参数识别方法的精度;最后给出了与建筑抗震规范相对应的不同场地、不同烈度下多遇和罕遇地震的谱强度因子.

The time variable spectrums of strong earthquake records were estimated by harmonic wavelet transform.The characteristic of time variable spectrum of the earthquake records from different sites of three classes being compatible with seismic code were analyzed.Results show that the records in the sites it harder soil have longer stationary duration during the time domain,and have higher frequency center and widen frequency band.The average time variable spectrums of earthquake records were simulated by uniform non-stationary stochastic model.The empirical formulas for the time variable spectrums of the earthquake records on three classes of sites soil are established by using nonlinear function fitting method.In order to demonstrate the precision of the simulated stochastic model,an error function is defined,and the error values are calculated finally,the value of the time variable spectrum factors corresponding to the earthquake intensity degree and site soil class which are compatible with the seismic code are given.