近断层脉冲型地震动的模拟方法

近断层地震动的向前方向性效应和永久地面位移效应导致其速度时程表现为长周期、大峰值的速度脉冲，其位移时程表现为阶跃型脉冲. 针对这些特点，同时考虑向前方向性效应和永久地面位移效应，提出了一种简单的、连续函数形式表达的等效速度脉冲模型. 在该模型中，包含描述速度脉冲周期、峰值和形状的5个待定参数，方便了实际脉冲型地震记录的拟合及模拟. 等效速度脉冲模型只包含单一的频率成分，不能反映脉冲型地震记录的高频成分. 根据对11次地震28条地震记录的分析， 速度脉冲的频率一般小于1Hz. 因此， 在模拟脉冲型地震记录的方法中，分别模拟低频脉冲成分和高频成分，并将两者叠加生成近断层脉冲型地震动的模拟时程.

SIMULATION METHOD OF NEAR-FAULT PULSE TYPE GROUND MOTION

The two characteristics of near-fault ground motions, i.e., the forward directivity effect and permanent displacement effect, result in long period and large velocity pulse in the velocity time history and large step pulse in the displacement time history. Considering the two effects, a simple expression of continuous function for equivalent velocity pulse time history is presented in this paper. The equivalent pulse model, in which the pulse period, peak velocity and pulse shape are described by five parameters, is highly advantageous to fit and simulate the pulse-type velocity time history. The equivalent pulse model comprises only one low-frequency component while the high-frequency component of a pulse-type earthquake record cannot be considered. Based on 28 records of 11 earthquakes, the pulse frequency of pulse-type records is generally less than 1 Hz. Therefore the low-frequency component and high-frequency component are simulated respectively and combined them together to generate a pulse-type ground motion.