Decomposition and modelling of the BC87 dataset

The BC87 data exhibit distortions due to three-dimensional structures at almost all scale sizes. The distortion- and level-corrected data are modelled using both 2D forward trial-and-error fitting and Occam2 smooth inversion. The crustal section of the resulting models correlates well with some geological features. However, the long period phase difference between the E- and B-polarization lasting for more than a decade is difficult to intepret without recourse to introduction of a layer with differing electrical conductivity in the two orthogonal horizontal directions, ie an anisotropic layer. -from Authors