Marine CSEM signal propagation in TIV media

Abstract

In marine CSEM and SBL the seabed subsurface is explored by emitting low‐frequency signals from an electric dipole source which is towed close to the seabed. The main goal is to detect and characterize possible thin resistive layers within the conductive surroundings beneath the seabed. Investigations of how the response from a resistive reservoir varies with characteristic parameters such as layer thickness and conductivity can be made using standard numerical modeling tools. However, the response from a thin resistive layer can be described by explicit spatial expressions that are derived by analyzing the CSEM field integrals with asymptotic methods. To gain understanding and physical insight into how CSEM signals propagate, it is informative to obtain and analyze such spatial expressions. I here present spatial expressions for the electromagnetic field responses from a thin resistive layer in transversely isotropic media, and furthermore discuss how the analytic expressions can be used in interpretation of marine CSEM field data.