利用慢衰减高频电磁波的逆散射进行电磁法测深的可行性理论研究

Study on Feasibility of Using Backscattering of Slowly Decaying High-frequency Electromagnetic Wave in Electromagnetic Method

常规电磁法测深一般是利用低频电磁波来进行探测,分辨率很低,无法满足测深要求。慢衰减电磁波是一种利用特殊函数作为波源来实现的高频电磁波,它除了具有衰减慢的特点外,还具有波束窄、能量集中的特点,在军事和通信领域已经得到了广泛的应用。慢衰减电磁波的衰减比一般电磁波慢,可以实现较大的探测深度;由于它的频率高,可以实现较高的分辨率。因此,可以利用它来进行地球物理探测。着重论述了利用慢衰减电磁波的入射波和散射波的振幅关系,以及电磁波的走时关系反演地下介质参数的基本原理及方法,同时,针对火成岩、变质岩和沉积岩,通过正演理论计算,说明了慢衰减电磁波测深的可行性。

Normal electromagnetic method usually uses low-frequency to explore, which has less resolving power to meet request. Slowly decaying wave is a kind of electromagnetic waves which use special function as their sources. They not only have the quality of slow decay, but also narrow beam and focused energy, which are widely used in military and communication. For these qualities, when they are used in geophysical exploration, the depth and resolution of investigation can be improved. This paper particularly focuses on the theory and implementation of how to inverse underground structure by comparing incident wave and scattering wave, and recording the spare time of the waves, and forward calculations for igneous, metamorphic and sedimentary rocks are carried out to verify the feasibility.