Calculation of full-waveform airborne electromagnetic response with three-dimension finite-difference solution in time-domain

The full waveform airborne electromagnetic exploration has become a trend of new-generation airborne electromagnetic exploration, due to its advantages of high-precision interpretation and high-resolution. This paper is based on the passive finite-difference solution to decompose the transmitter current into several small trapezoid impulses, and transform the electromagnetic field excited by these trapezoid impulses in time-domain into initial field in space. During the iteration step, finite-difference equations are introduced in the finite-difference equations. It transforms the active finite-difference equations into passive finite-difference equations gradually. It will work out the calculation of full-waveform airborne electromagnetic response with three-dimension finite-difference solution in time-domain eventually, when the transmitter current is in arbitrary waveform. The results show that the stabilization time of calculation for the airborne electromagnetic response of typical geoelectric models in air time-domain can exceed 10 ms with trapezoid-wave transmitting. Compared with the integral equation solution, the average error of response of second field in the center of transmitter coil is less than 1%. The realization of full-waveform three-dimension finite-difference solution provides a foundation for full-waveform three-dimension inversion and equipment design.