Abstract:Traditional controlled source electromagnetic methods (CSEM) typically collect specific single-component of the total magnetic field intensity, leading to zero-value bands, narrow azimuthal detection ranges, and angular detections. An innovative detection strategy that utilized both the horizontal and total magnetic field intensities was introduced in this work. Numerical simulations were conducted to analyze the impact of sensor angular deviations on single-component and horizontal magnetic field intensities. Notably, the horizontal magnetic field intensity remains unaffected by horizontal angle deviations, while the total magnetic field shows resilience to all angular deviations. Theoretically, orthogonal magnetic sensors could facilitate wide-azimuth magnetic field detection. Results from field experiments revealed a pronounced anomaly response of both the horizontal and total magnetic field intensities to underground caverns. These experiments demonstrated a significant reduction in issues related to angular deviations in magnetic sensors and confirmed the feasibility of wide-azimuth magnetic field detection. The proposed wide-azimuth detection method has the potential to extend the detectable angle from that of CSEM to 360°, resolves the issue of angular deviation of magnetic sensors, and thus improves the detection accuracy.

Key words: controlled source electromagnetic method; wide-azimuth; magnetic field; zero-value band; angular deviation