Inversion of the data The RAMESSES Experiment III: Electric field decomposition

Modelling the data

The Reykjanes Ridge data extend from source-receiver offsets of 0 km to 15 km, covering a variety of geometries. Data at ranges of less than 1 km were not analysed because they have only a limited sensitivity to crustal structure, and are affected to a greater extent by errors in source and receiver position. Although 2-dimensional inversion is in principle feasible (Unsworth & Oldenburg, 1995), existing implementations are not able to handle realistic experimental geometries and seafloor topography. Our approach is therefore to invert subsets of the data in 1-dimension using the Occam algorithm implemented for seafloor CSEM data by Flosadottir & Constable (1996), and use the results as a guide to iterative 2-dimensional forward modelling using the finite element modelling code of Unsworth (1991) (described also in Unsworth etal, 1993), modified for the purpose of this study to include realistic seafloor topography.


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