Cabled Marine Magnetotellurics: Denser Data at Lower Cost and Higher Information Content

Egbert, Gary (Oregon State University) | Meqbel, Naser (GFZ Potsdam) | Strack, Kurt (KMS Technologies)



With the increasing success of marine electromagnetics, the trend is to go to similar acquisition density as with seismic data. Cabled marine controlled source electromagnetic (CSEM) systems under development will make acquisition of dense CSEM datasets for seafloor exploration practical. Natural source EM data, which may also be collected by such systems for essentially no additional cost, have the potential to refine and confine the interpretation of the CSEM data in complex and variable geologic environments. However, to reduce costs and maintain operational efficiency in a cabled system only some components of the EM fields may be collected, so that the configuration of sampled data may be non-standard for classical magnetotellurics. Specifically, spacings will be closer but not all components are measured at every site. Here we use 3D synthetic data inversion experiments to explore impacts on target recovery of (1) sampling density, and (2) exclusion of specific transfer function components. We show that including magnetic field TFs almost completely compensates for exclusion of impedance components associated with cross-profile electric fields, which would be more challenging to collect with a cabled system.