一段随运动路径变化的带有箭头的曲面片，沿两个圆环合并起来的8字形滑道，不断来回滑动-A path of change with the movement of surface patches with arrows along the two rings combined 8-shaped slide, slide back and forth

在前人工作的基础上对三层层状介质的瑞利波频散曲线进行了正演模拟研究，对假定的几组典型模型参数的频散曲线进行了认真分析。通过分析可知，各频散曲线之间是互不相交的，从而对此问题有了一个更清晰的认识。指出当低速软弱夹层存在时频散曲线的特点，并根据分析结果，说明”之“字形频散曲线的形成机理。(On the basis of previous work, the Rayleigh wave dispersion curves of three layered media are studied by fo