FULL TRANSMITTER WAVE-FORM TRANSIENT ELECTROMAGNETIC MODELING AND INVERSION FOR SOUNDINGS OVER COAL MEASURES

Modeling of transient electromagnetic soundings requires consideration of the full bipolar transmitter waveform in order to obtain full measurement accuracy from field instruments. The full-waveform transient may be computed using existing impulse-response forward algorithms followed by a convolution procedure with truncation and residual estimation after an even number of terms, which results in average increases in run time of about 80 percent. Examples of soundings over moderately conductive coal measures and highly conductive cindered coal show that failure to use the full waveform yields depths and resistivities biased to erroneously high values. The bias is small in the former case, but produces substantial errors in the latter case.