近断层脉冲型地震动功率谱特性分析

Characteristic analysis of power spectrum for near-fault impulse type ground motion

计算分析了近断层脉冲型和无脉冲地震动的功率谱特性。与远场地震动相比,近断层脉冲型地震动的功率谱峰值最大,且在低频处能量集中,符合其长周期分量丰富和幅值大的特点;无脉冲地震动的功率谱峰值次之,对应的卓越频率大于脉冲型地震动功率谱的卓越频率,但仍小于远场地震动功率谱的卓越频率。建立了一种新的功率谱模型以拟合近断层地震动的平均功率谱,并得到了谱强度因子关于震源幅值系数、传播介质衰减系数和震中距的表达式。最后,从新的视角对近断层和远场地震动功率谱卓越频率产生差异的原因进行了诠释。

The power spectral density （PSD） of near-fault impulse type and non-impulse type ground motions were computed and analyzed. Compared with the far-field ground motions, the near-fault impulse type ground motions has the maximum power spectrum peak value and more energy concentration in the low-frequency region, which is consistent with the properties of abundant long-period contents and large amplitudes. Meanwhile, the non-pulse ground motions has the medium power spectrum peak value and its corresponding dominant frequency is greater than that of impulsive one but still less than that of far-field ground motion. Moreover, a new power spectrum model was established to fit the average power spectrum of near-fault ground motions, and the expression of spectral intensity factor with respect to the seismic source amplitude coefficient, the propagation medium attenuation coefficient and epicentral distance was achieved. Finally, the reason for the difference of dominant frequency of power spectrum between near-fauh and far-field ground motions was illustrated from a new perspective.