地震波场的复射线展开

SYNTHESIS OF SEISMOGRAM BY COMPLEX RAY EXPANSION

利用复射线理论将惠更斯原理推广到复空间,发展出一种简便的波场计算方法.本文以均匀柱面波在平界面上的反射场为例,用复射线展开法计算了时谐地震波及瞬变地震波在部分反射、全反射和临界角过渡区的场分布,并与平面波谱积分结果进行了比较.结果表明,用复射线展开法可以自动平滑过渡区反射场的奇异性,因而该方法可直接处理焦点、焦散线和全反射过渡区等复杂的波场分析与综合问题,并可简化数值计算过程.

Huyghens' principle is extended into complex space by complex ray theory, and a simple method for wave field computation is developed As an example, an isotropic cylindrical seismic wave (harmonic or transient) reflected at a plane interface is considered. The field distributions in regions of partial reflection, totally internal reflection and critical reflection aie evaluated by this method, and compared with the results from plane wave spectral integral. It is shown that complex ray expansion can take care of the field singularity in the transition region automatically. Therefore, the method may be employed to deal with the complicated wave-field analyses and syntheses in focal, caustic, and transition regions with simplified numerical calculations.