Amplitude Effects of Magnetic Signals on Depth Estimation Routines

Increased acquisition of geophysical data in conjunction with limited geological information places greater importance on accurate geophysical processing and interpretation methodologies. There are numerous semi-automated data processing routines presently being implemented which specialize in location, geometry, and depth of potential source bodies. Most routines rely on the innate relationship that magnetic signal frequency is a function of a magnetic source’s depth and geometry. An additional relationship that is often not addressed is amplitude, which is a function of a source’s magnetization. Most analytic routines incorporate some sort of mathematical entity in their fundamental equations to address magnetization effects. However, there are associated limitations of these analytic routines that must be clearly defined to accurately interpret the calculated results. The mathematical expression of tilt-angle has recently been developed into a depth-estimation routine, known as “tilt-depth”. It has been shown to work reliably on sources that generate non-complex anomalies, which include a non-dipping body under the influence of a vertical magnetic field vector. It is important to consider how depth estimations will be effected when the amplitude of the source magnetization varies. Tilt-depth solutions become more inaccurate once the source approaches the surface and increases in magnetization. This is due to the creation of more complex signal geometry and reiterates the premise that the limitations of any of depth estimation routines must be considered and mitigated.