广州近郊地热勘查中音频大地电磁干扰特点的分析及处理

Analysis and treatment of audio frequency magnetotelluric interference in geothermal exploration in suburbs of Guangzhou

音频大地电磁法是目前地热勘查中常用的一种方法,由于其采集的为天然交变电磁场信号,极易受到电磁噪声干扰。以广州市郊地热勘查项目采集的音频大地电磁数据为例,对该地区的人文噪声进行了分析,认为研究区内干扰复杂,主要包括尖峰噪声、方波噪声、脉冲噪声、三角噪声以及阶跃噪声,以上形式的噪声组成了研究区内的近场源干扰;基于MTsoft^(2D)处理软件,认为近场源干扰对剖面的影响由浅至深逐渐增大,造成反演电阻率纵向拉伸,异常呈近直立状,在数据处理及反演之前剔除近场源干扰,可以避免干扰数据参与反演计算,在一定程度上提高反演效果。

Audio frequency magnetotelluric method is a common method in geothermal exploration.Because it collects natural alternating electromagnetic field signals,it is very easy to be disturbed by electromagnetic noise.Taking the audio magnetotelluric data collected by the geothermal exploration project in the suburbs of Guangzhou as an example,this paper analyzes the humanistic noise in this area.It is considered that the interference in the study area is complex,mainly including peak noise,square wave noise,impulse noise,triangular noise and step noise.The above forms of noise constitute the near-field source interference in the study area.Based on the MTsoft^(2D)processing software,it is considered that the influence of near-field source interference on the profile gradually increases from shallow to deep,resulting in the vertical stretching of inversion resistivity,and the anomaly is nearly vertical.Eliminating the near-field source interference before data processing and inversion can avoid the interference data from participating in inversion calculation and improve the inversion effect to a certain extent.