摘要:
针对可控源音频大地电磁法( CSAMT)野外数据采集中接收电缆线之间、接收电缆线和大地之间存在的电磁耦合效应,通过电磁耦合理论研究和等效电路计算,推导正演模拟计算公式,结合各种模型的正演模拟计算和野外实际数据对比,研究了可控源音频大地法中影响电磁耦合效应的三种因素,包括:电缆线长度、不极化电极接地电阻、信号频率,总结出三种因素对应的电磁耦合特征,即:接收系统中电缆线长度越长,电缆线之间的耦合电容越大,视电阻率曲线在高频段出现下降的趋势越明显,曲线畸变越明显;野外不极化电极上接地电阻越大,视电阻率曲线在高频段表现出下降的趋势越明显,曲线畸变越明显;电路中信号频率越高,感抗和容抗越大,曲线畸变越明显,当信号频率增大到一定的值时,电路中的感应容抗就不再继续增大,曲线趋于稳定。
Abstract:
In the light of the electromagnetic coupling effect between the receiving cables and between the receiving cable and the earth in data collection in CSAMT and through electromagnetic coupling theory and equivalent circuit calculation,the authors derived the for?ward modeling formula. Based on a variety of models and forward simulations in comparison with actual field data,the authors studied three factors affecting electromagnetic coupling effects in CSAMT,i.e., cable length, ground resistance of non?polarized electrode, and signal frequency, and summarized three kinds of phenomena corresponding to electromagnetic coupling characteristics: the longer the cable of receiving system, the larger the electromagnetic coupling effects between the cables, the more obvious the distortion of apparent resistivity curve in the high frequencies, and the more evident the distortion of curves;the bigger the ground resistance of non?polarized electrode, the more obvious the distortion of apparent resistivity curve in the high frequencies, and the more evident the distortion of curves;the greater the signal frequency, the larger the inductance and the capacitance, and the more obvious the distortion of curves. When the signal frequency increases to a certain value, the capacitance and the inductance no longer continue to increase, and the curves tend to be stabilized.
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