瞬变电磁合成孔径成像方法研究

瞬变电磁法虽然广泛应用于资源勘探和工程勘察中,但仍存在一些亟待解决问题.迫切需要引进一些新的技术与方法,以进一步提高解释精度.由于瞬变电磁资料可以通过数学公式转换成虚拟波;多孔径瞬变电磁物理模拟证明TEM多孔径具有相干性;相邻位置上同一地质体的反射回波具有较好的相关性.所以,对于瞬变电磁资料可以进行多孔径合成成像.本文借助于合成孔径雷达的基本思想,提出一套新的数据处理方法,即采用相关叠加技术,实现多孔径数据合成.在完成瞬变电磁虚拟波提取后,将传统的以剖面为主的处理方式发展成为以测点为中心的多孔径合成,将传统的以单点处理方式发展成为逐点推移多次覆盖的处理方法.采用相关叠加的方法来进行合成孔径,由此大大提高瞬变电磁法的分辨率.从波场的角度拓展和丰富了瞬变电磁场的内涵,使得从实测资料中提取到常规瞬变电磁法提取不到的信息,对地下目标体成像更为有利.通过对所设计模型和实测资料处理,结果表明合成孔径成像效果较好.研究成果为发展瞬变电磁成像技术,提高分辨率提供了一条新途径.

A research on TEM imaging method based on synthetic-aperture technology

Although Transient Electromagnetic Method(TEM) has been widely used in resource exploration and engineering exploration,it still has some problems to be solved.In order to improve the interpretation precision,some new techniques and methods must be introduced.Because TEM data can be converted into a virtual wave-field by a mathematical formula;the achievement of multi-aperture electromagnetic model simulation shows that the correlation of multi-aperture TEM does exist;echo waves of the same geological body from adjacent positions have a good correlation.Therefore,it is feasible for TEM data to realize multi-aperture synthesis imaging.With the basic idea of synthetic aperture radar,a new set of data processing methods have been proposed which use related superposition techniques to fulfill multi-aperture data synthesis.After the extraction of transient electromagnetic pseudo-wavelet,the traditional profile-based approach has been developed into the multi-aperture synthesis relative to measuring points,and the traditional single-point approach has been developed into the point-by-point survey multiple coverage technique.The technology of synthetic aperture thereby greatly improves the resolution of transient electromagnetic method and enriches the connotation of it from the perspective of wave-field.Thereby,more information can be extracted from the transient electromagnetic method which can not be got by conventional methods and it′s more beneficial to imaging.It has been shown that synthetic aperture imaging is feasible from the processing results of designed models and measured data.The research achievement opens a new approach to develop transient electromagnetic imaging technique and improve the resolution.