瞬变电磁法对存在山谷地形时的多个异常体的探测能力研究  

THE DETECTABILITY OF TRANSIENT ELECTROMAGNETIC METHOD TO MULTIPLE 3D BODIES WITH VALLEY TOPOGRAPHY

作　　者：唐新功[1] 胡文宝[2] 严良俊[2] 

机构地区：[1]北京大学地球物理系,北京100871 [2]中国石油天然气集团公司物探重点实验室长江大学研究室,荆州434023

出　　处：《地震地质》2005年第2期316-323,共8页Seismology and Geology

基　　金：国家自然科学基金(40174040)资助。

摘　　要：以层状地层中的2个三维导电薄板为例,考虑了山谷地形存在时,瞬变电磁法(TEM)分辨地下多个三维异常体的能力。模型计算的结果表明,当有山谷地形存在时,总的异常场由薄板的异常和地形的异常叠加在一起,表明异常场在空间上具有可加性质。在地形平坦时,TEM方法对相同尺寸的近源异常体的分辨能力要优于远源,而且离源越远的异常体异常越小,最后直到无法分辨。但是当存在山谷地形并且把源放在其中时,它们的总异常场叠加后会“放大”远源异常体的异常场,在一定意义上说,这对于分辨远处的异常体更加有利。当异常体在接收器下方埋深不是太大时,不论山谷地形在源处还是接收器处,TEM法对这些异常体的探测能力都是比较好的。2个异常体相距太近时,其异常会叠加在一起,给TEM的分辨增加一些困难。总体表明,在有山谷地形存在时,TEM方法对多个异常体仍具有较好的探测能力。The delectability of transient electromagnetic method (TEM) to multiple 3D conductive sheets with valley topography is discussed in detail in the paper. An anomalous body with a resistivity of 10^(6)ohm.m is designed to simulate the valley topography. The results of the modeling illustrate that the total anomalous fields are the summation of anomalous fields produced by the valley and the conductive sheets. The delectability of TEM to the conductive sheets buried shallower beneath the receivers is quite good without valley topography and TEM is much more sensitive to anomalies near the source than those far from the source. It is interesting that the total field will enlarge the anomalies fields of those conductive sheets placed in far source when the valley topography exists and, in some sense, this will be helpful for TEM to detect the anomalies from far source. The delectability of TEM will become weaker when the distance between two anomalous bodies is too small. In general, the delectability of TEM to multiple 3D conductive sheets is still good when valley topography exists.

关 键 词：山谷地形 瞬变电磁法 探测能力 异常体 异常场 导电薄板 层状地层 模型计算 分辨能力 TEM法 接收器 叠加 三维 埋深 

分 类 号：P425.2[天文地球—大气科学及气象学] P631.325