强震地面运动的混沌特性分析

引入非线性动力学理论和混沌时间序列分析方法考察强震地面运动加速度时程的非线性特征。首先采用功率谱分析法、主成份分析法和Cao方法定性判断地震动加速度时程具有混沌特性，然后应用混沌时间序列分析方法定量计算了30条地震动加速度时程的三个非线性特征参数。计算表明，这些地震动时程的关联维数为2．0～4．0的分数维，Kolmogorov熵K2为大于零的有限正值，最大Lyapunov指数在o～i．0之间。结果说明，强震地面运动具有混沌特性，地震动的高度不规则和复杂性是地震过程强非线性的反映。

Chaotic Characteristic Analysis of Strong Earthquake Ground Motions

The nonlinear dynamic theory and the chaotic time series analysis method were adopted to examine the nonlinear characteristics of strong earthquake ground motions in this paper. Based on the power spectrum analysis, principal component analysis, and Cao＇s method, the acceleration time series of ground motions have been determined qualitatively being of the chaotic property. Then, the chaotic time series analysis method is applied to calculate quantitatively the three nonlinear characteristic parameters of 30 records of ground acceleration. Numerical results show that the correlation dimension of these ground motions is a fractal dimension between 2.0 and 4.0. Their Kolmogorov entropy K2 is a finite value larger than zero, and their maximal Lyapunov exponent is in the interval 0-1.0. The result has demonstrated that the strong ground motions possess the chaotic character, and the severe irregularity and complexity of ground motions are the reflection of high nonlinearity of earthquake process.