Inversion of arbitrary segmented loop source TEM data over a layered earth

• Proposing an alternate method to directly calculate the response and sensitivity for an arbitrary segmented loop source.
• Demonstrating the necessity to consider the change of loop geometry during the processing of the loop source TEM data.
• Validating our inversion scheme which incorporates the effect of the loop geometry on synthetic data set.
• Applying our inversion routine to the field data and obtained result consistent with the geological model.

The loop source TEM method has been widely used in the detection of a mined out area in China. In the cases that the laying of traditional rectangle or square transmitting loop is limited due to the presence of obstacle on the path of the loop, the changing of the shape of the transmitting loop to bypass the obstacle is a labor saving solution. A numeric integration scheme is proposed to calculate the response and Jacobian of the segmented loop source from that of an electric dipole source. The comparison of forward response between the segmented loop and square loop shows the effect of loop geometry on the decay curves. In order to interpret the data from an irregular source loop, this paper presents an inversion scheme that incorporate the effect of loop geometry. The proposed inversion scheme is validated on the synthetic data, and then applied to the field data. The result reveals that the developed inversion scheme is capable of interpreting the segmented loop source TEM field data.