Coast effects on magnetic and magnetotelluric transfer functions and theircorrection: application to MT soundings carried out in SW Iberia

The coast effect on magnetic and magnetotelluric data acquired near the SW coast in the Iberian Peninsula was investigated using three-dimensional mod elling. The ocean was modelled as a layer with constant conductivity (0.3 o hm m) and thickness of 3.5 km. The continental resistivity model was constr ucted taking into account its electrical structure obtained from previous m agnetotelluric studies. The model shows that the ocean-coast effects are im portant for periods greater than 100-300 s tin this case), affecting both t he induction vectors and the impedance tensors. A method for the correction of the coast effects on the impedance tenser is presented. Synthetic data generated from a model including coast effects were corrected using the met hod and compared successfully with data not showing those effects. As an ex ample the correction has been applied to some magnetotelluric soundings car ried out in SW Iberia. (C) 2001 Elsevier Science B.V. All rights reserved.