By defining a total reflection coefficient of natual EM field over multi layered medium, the forward and inversion equations for nature soutce EM sounding are established.
引入一个多层岩层相叠时其表面对电磁波入射的总反射系数的概念，从而导出了方法的正反演计算式及相应仪器的设计方案，并制造了测深仪器。