斜阶跃场源瞬变电磁法的全程视电阻率数值计算

推导了斜阶跃场源激励下采样零时刻在发射电流关断处的均匀导电半空间瞬变响应解析式,分析了斜阶跃场源激励下的磁场、感应电压与视电阻率的对应关系,指出用感应电压定义的全程视电阻率可能存在无解或多解的情况。提出了一种全程视电阻率直接计算方法,将发射电流关断时间作为系统参数参与视电阻率的计算,可以方便地计算出中心回线装置下测量目标的全程视电阻率。理论模型的分析与Electromagnetic Model Analysis软件计算数据的比较证明了这种数值算法的可行性。不同于常规数据校正算法,提出的全程视电阻率直接算法具有更小的误差和更快的计算速度,由于斜阶跃场源技术的成熟,该算法具有一定的应用价值。

Numerical Calculation of All-Time Apparent Resistivity for Ramp Transient Electromagnetic Method

In this paper, the transient response of a homogeneous half-space excited by a ramp current waveform is proposed for time zero selected as the end of the turn-off ramp. Based on the transient response analytic expression, the relationship between apparent resistivity, voltage and magnetic field is discussed. The relationship shows that computation with the voltage may lead to multiple or no apparent resistivity. Aimed at central loop array, a method calculating the all-time apparent resistivity is proposed,which use the turn-off time as one of the system parameters. A simulation and further comparison with electromagnetic model analysis prove the validity and feasibility of this method. Compared to conventional correction methods, this direct numerical method is more accurate and costless computation time. With the development of linear ramp turn-off source, this method is of important practical values.