An Enhanced Tilt Depth Method for Interpreting Magnetic Data over Vertical Contacts of Finite Extent

Depth to basement estimation methods using various components of the spectral content of magnetic anomalies are in common use by geophysicists. Most simple models used for this purpose have the base of the magnetic body at infinity. Recent publications have shown that this ‘infinite depth’ assumption is responsible for generating anomalously shallow solutions. This has been shown both in theoretical and real data with seismic or well control. The Tilt-depth method is one of the depth estimation methods which is now commonly used since the depth estimates are based on the spectral content of single anomalies. To overcome the limitation of infinite depth this contribution presents the mathematics for a finite depth contact body and applies it to a continental USA example where the bottom of the magnetised basement is probably at the Curie isotherm or for simplicity the Moho. Since both these depths are large the error in the depth to top basement is small but never-the-less under estimated. The other example used is over the central Red Sea where the Curie isotherm and Moho are shallow. The difference in the depth estimation between the Tilt-depth and Finite Tilt-depth is such a case is significant and can exceed 200%.