航空瞬变电磁数据背景场去除研究

Background field removal from airborne transient electromagnetic data

与地面瞬变电磁法相比,航空瞬变电磁法受不同的噪声类型影响较大,如天电噪声、运动噪声等,并且背景场对数据的影响也是不可忽略的。由于背景场中含有一次场信息,使得背景场幅值远大于含有地质信息的二次场信号。为较清晰地获得地下电性结构,需找到可以高效去除背景场的方法。本文提出利用线性插值方法来对背景场问题进行研究。首先,获得前、后高空飞行的测线数据,经过叠加、平均计算得到叠加周期内相同采样时间道的响应值,然后,利用插值原理针对每个采样时间道建立一个插值函数,最后,根据飞行时间来计算工区每条测线上采集数据的背景场值,从而达到去除背景场的目的。实测数据背景场去除的算例表明,该方法可较好地去除背景场对二次场异常的掩盖,去除后可较清晰地判断异常出现的位置。时间域航空电磁数据预处理包含较多处理模块,该方法的提出为高效的数据处理奠定了基础。

A comparison with ground transient electromagnetic(EM)method shows that airborne transient EM is more affected by noise,such as sefrics and motion noise.And the influence of background field noise couldn't be neglected.The background contains primary field information,which causes the amplitude of background field to be much larger than the secondary field signal containing geological information.In order to obtain the underground electrical structure clearly,it is necessary to find an efficient method to remove background field.In this paper,the background field problem is studied by linear interpolation.First,according to the responses of the front and back line obtained from the high flight,after cumulative and average calculation,the responses of the same time channel of each measured line in a cycle can be obtained as the background field responses of the corresponding time channel of each line.Using interpolation principle,the background field above each measuring line in the working area is calculated by flight time,so as to remove the background field.Through the real data removal,this method can better remove the background field and then show the anomaly,and can clearly determine the location of the anomaly after removal.Time-domain AEM data preprocessing contains many processing modules.The linear interpolation method proposed in this paper lays a foundation for efficient data preprocessing.