On: “Results of a controlled‐source audiofrequency magnetotelluric survey at the Puhimau thermal area, Kilauea Volcano, Hawaii, by L. C. Bartel and R. D. Jacobson (GEOPHYSICS, 52, 665–677, May 1987)

Abstract

A growing number of papers being published on the CSAMT-MT curve transformation, which — as the authors state — allows a simpler magnetotelluric interpretation of the corrected CSAMT curves. The concept of near‐field corrections is based on electromagnetic relations over a homogeneous earth, and the effects of subsurface layers or lateral inhomogeneities are usually neglected. Bartel and Jacobson (1987) especially suppress the bounds of the near‐field correction: After presenting several near‐field correction curves over a homogeneous earth in their Figure 2 (which includes an idealistic demarcation line instead of a gradual change between near‐field and far‐field regions), they simply add that “…for a layered earth a similar demarcation occurs between the far‐ and near‐field regimes.” Further, the problem of lateral inhomogeneities is not mentioned in the paper. Such a description might lead to an oversimplification. I should like here to underline both limitations.