Sensitive characteristics of contributed region and detectability analysis for semi-airborne frequency-domain electromagnetic system

Abstract

There is restricted research on the sensitive characteristic and detection ability analysis of semi-airborne frequency domain electromagnetic system at present. However, it is critical to the optimal design of the observation scheme, and it may be beneficial for the optimal selection of the record region and increasing the resolution of apparent resistivity imaging. So it is necessary to analyze the sensitive characteristic of the semi-airborne frequency domain system. In this paper, the primary electric field based on the closed-form expression of the electromagnetic field in the underground excited by a horizontal electric dipole is calculated, each element of the underground will be regarded as a current source, and the secondary magnetic field can be obtained based on tensor Green's function. The sensitivity is defined by the contribution of each element to the total secondary magnetic field at the receiving point, and the sensitivity distribution characteristic of the related region is analyzed. Numerical experiments reveal that the region with high sensitivity can produce a strong relative anomaly, and the contribution of the region with sensitivity near zero is almost negligible. To verify the analysis for sensitive characteristics and detectability, we have conducted a field test, after the design of the observation scheme, the data obtained reflects the underground fault zone well. Thus, the relationship between detectability and sensitivity is worth studying.