基于频率-波数域算法的理论地震波形图方法，可以数值模拟频率达到10 Hz、震中距达1000 km 的区域理论地震波形图。该算法适用于计算大量分层地壳结构中激发的导波Lg 波。本文在前苏联东哈萨克斯坦地下核试验场至我国乌鲁木齐台站间的地球介质速度模型中，引入速度梯度结构、速度扰动分布的薄叠加层结构、降低 Q 值结构以及速度扰动与 Q值变化的综合结构来模拟实际地壳波导结构，较好地模拟出东哈萨克斯坦地下核爆炸地震在乌鲁木齐台站记录的宽频带地震波形图，模拟出完整的 Lg 波序列，该序列符合 Lg 波能量分布特征，且能够解释 Lg 波波尾的特征。结果表明，Lg 波的形状和峰值结构均依赖于地壳的不同波导结构。%Based on the frequency-wavenumber algorithm,we can simulate high frequency (10 Hz)regional seismograms (up to a distance of more than 1 000 km).The algorithm is used to synthesize the regional waveguides on Lg waves in a medium consisting of a large number of crustal layers.Based on the crustal velocity model from a former Soviet nuclear test site located in eastern Kazakhstan to WMQ station in China,this paper build up a modified model con-sisting of thin layers with an alternating high and low-velocity,a velocity gradi-ent near the surface,the lower Q values,and the composite structure of velocity perturbation and different Q values so as to match the real crustal structure. And then we simulate very well the regional seismograms in WMQ station by underground nuclear explosions of the test site in eastern Kazakhstan.The syn-thetic results conform to the energy distribution characteristics of Lg waves, and explain the feature of the coda.The numerical results suggest that the shapes and peak amplitudes of Lg waves all depend on the different crustal waveguides.
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