Redatuming of borehole-to-surface electromagnetic data at the Kevin Dome exploration site
The method of redatuming the controlled-source electromagnetic data was introduced in Zhdanov and Cai (2012). The approach is based on a Stratton-Chu type integral and the Lorentz lemma to relate observed EM data on the earth’s surface to EM data on some horizontal plane P located underground. By applying this methodology, we are able to calculate the EM scattering field at some depth from the observed data on the earth’s surface. Once the EM field at some underground plane P is found, we can use these data for upward continuation and recomputing of the EM scattering data on the earth’s surface. This upward continuation problem is always well posed. By doing this, we can place more virtual receivers at the earth’s surface and within a much larger area. Compared to traditional interpolation and extrapolation techniques such as polynomial fitting or spline approximation, our method takes into account the physics of the EM field, which makes the redatuming more accurate than simple mathematical transformation. In this paper, we illustrate this method by redatuming of borehole-to-surface electromagnetic data at the Kevin Dome exploration site.