Inverse wavefield transform for the magnetic components of the loop-source transient electromagnetic data

We present a newly inverse wavefield transform for the vertically magnetic components of the loop-source transient electromagnetic (TEM) data. Based on the wavefield transform between the electromagnetic (EM) diffusion and the fictitious EM wave, the transform formula of the TEM field and its time derivative are presented. To numerically accomplish the inverse wavefield transform in a finite interval, the shortest time window for the pseudo-wavefield is determined by a newly proposed formula. Then the pseudo-time window can be directly figured out according to the time window of TEM measuring time. To solve the inverse wavefield transform equation accurately, the precise integral method (PIM) is introduced. In the numerical results, the pseudo-wavefield traces transformed from the modeled TEM responses are physically rational as the pseudo-wavefield reflection arrives as expected. The data misfit between the fitted and the modeled data is smaller than 0.01% for the B(t) components. The transformed pseudo-wavefield is physically rational and numerically accurate to highlight the location and features of the electric interfaces.