Distortions of Metallic Objects in EM34 Apparent Conductivity Readings

• DOI: 10.32389/jeeg21-029
• Publication Date: 2025-01-07T14:39:36Z
• Authors: Pedro Henrique da...; Caroline Urenha S...; Carlos Alberto Me...; Ulrich Ofterdinger
• Keywords: Fence (mathematics)

Metallic structures are a common noise source in Slingram electromagnetic surveys because they interact with the primary magnetic field generated by transmitter coil and create secondary that distorts apparent conductivity readings from layered or homogeneous subsurface. The main challenge is understanding how their influence varies depending on loop configuration distance at which surface structure no longer readings. We propose methodology integrates experimental techniques numerical modeling to elucidate distortions induced fence-like placed varying distances coils of low-induction meter. Additionally, we aim evaluate model responses using simulations systems operating higher frequency ranges. To quantify conductivity, conducted measurements keeping fixed position while changing placement conductive structure. obtained before installing were used as background reference response accurately determine distortions. same procedure was tested terrains different resistivities changes caused backgrounds. Our results show this approach allowed us infer deviations presence fence more noticeable where resistivity higher. However, these observed only for short about 1/5 1/2 separation evaluated targets. integration between survey suggests distortion increases when instrument operated induction numbers than ∼0.2. For all models ranges, minor vertical coplanar compared horizontal transmitter-receiver pair. Negligible fences unconnected wires, suggesting interference loose metallic objects ground do not form closed loops, favoring EM induction.