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使用经验格林函数法估计了产生0.2～10 Hz 频率范围内地面运动的强运动发生区。强运动发生区比总破裂区要小一些,而且与凹凸体的面积一致,后者由低频(<1Hz)波形反演估计的不均匀滑动分布导出。我们证实了在震源区附近观测到的震源振幅谱随方位角和距离的变化,亦即破裂的方向性效应,它是由破裂传播方式和强运动发生区的大小控制的。我们发现,在破裂传播方向的台站上震源位移波谱比侧向台站有更高的拐角频率和更陡的高频衰减,与传播方向相反的台站上有相反的趋势。据此提出了沿径向传播的单向和双向破裂的强运动发生区的大小和平均拐角频率之间不同的关系式。
Empirical Green’s function method is used to estimate the strong motion area that produces ground motion in the frequency range of 0.2 ~ 10 Hz. The area of strong motions is smaller than the total rupture area and is consistent with the area of the asperities, which is derived from the non-uniform slip distributions estimated from the inversion of low frequency (<1 Hz) waveforms. We confirmed the changes in azimuth and range of the source amplitudes observed near the focal zone, that is, the directivity of the fracture, which is controlled by the mode of propagation of cracks and the size of the zone of strong motion. We find that the source displacement spectrum has a higher corner frequency and a steeper high frequency attenuation than the lateral stations at stations with a propagating direction of propagation, and there is an opposite trend on stations opposite to the propagation direction. Accordingly, different relations between the size of the strong motion occurring region and the average corner frequency of one-way and two-way ruptures propagating in the radial direction are proposed.