摘要
天然大地电磁场信号微弱,极化方向随机,极易受电磁噪声污染。矿集区人烟稠密、工业发达,区内强烈的工业、通讯、矿山、民用等电磁干扰严重污染了大地电磁测深数据。本文利用数学形态学从受严重污染的电磁场时间序列中提取出类方波、三角波、阶跃、脉冲和充放电5种典型噪声的波形,以不同的方式将这些噪声波形与区内基本未受噪声污染的测点(D1139)的电磁场波形叠加,对比分析了不同采样率加噪后D1139点的测深曲线的变化。结果表明:24Hz采样率,方波噪声、三角波噪声、阶跃噪声、充放电噪声等会使得视电阻率、相位曲线出现类似近源干扰特征,脉冲噪声使测深曲线出现畸变;320Hz采样率,方波没有明显影响,三角波、阶跃噪声、脉冲噪声使曲线部分频点出现跳变,而充放电噪声会使曲线出现类似近源干扰特征;2560Hz采样率,方波、充放电噪声没有明显影响,三角波、阶跃噪声、脉冲噪声则使曲线出现了不同程度的畸变。
Natural electromagnetic field has some disadvantages, such as weak signal, ran- dom polarization direction that are highly susceptible to electromagnetic noise pollution. Ore concentration area is densely populated and industrialized. The strong magnetic of de- veloped industry, telecommunications, mining use in the area heavily contaminated magne- totelluric sounding data. This paper using mathematics morphology extracted out five waveforms of typical noise from serious polluted electric magnetic field time sequence. The waveforms are class square wave, triangle wave, order leapt, pulse and charging and dis charging. Different methods are used to overlay these polluted waveforms and the unpollut- ed waveforms （Dl139）. The contrast analysis of different sampling rate after adding noise Dl139 points shows the changes of measuring deep curve. Results indicates that the five noises --24Hz sampling rate, square wave noise, and charging and discharging noise noise, triangle wave noise, order jumped will make apparent resistance rate and phase curve appeared similar near source interference features, then pulse noise makes measuring deep curve appeared distorted. 320Hz sampling rate and square wave have no obvious effect; triangle wave, order jumped noise, and pulse noise make part of frequency points variable; charging and discharging noise will make curve appeared similar near source inter- ference features. 2560Hz sampling rate, square wave, and charging and discharging noise have no obvious effect; triangle waves, step noise, impulse noise will have some different degree of distortion of the curve.
出处
《工程地球物理学报》
2014年第6期802-812,共11页
Chinese Journal of Engineering Geophysics
关键词
大地电磁测深
矿集区
强噪声
波形
采样率
magnetotelluric sounding
ore concentration area
strong noise
waveform
sampling rate
