Induction arrows from offshore floating magnetometers using land reference data

Induction arrows are a traditional output of magnetovariational experiments, and represent transfer functions used quantitatively in the inversion of geomagnetic depth sounding data to give Earth electrical conductivity structure. In this paper, a technique is tested in which 'total-field' variations are combined with horizontal-field data recorded simultaneously at remote stations in order to derive induction arrows. The method is first demonstrated using total-field data recorded on land by an aeromagnetic base station, and then applied to data obtained from magnetometers floated offshore on the sea surface. The floating magnetometers were deployed in two configurations: one tethered to the seafloor; the second free-floating.