Marine effects on vertical electrical soundings along shorelines

Abstract

Onshore applications of direct current resistivity (DCR) along shorelines suffer a short-circuit-like phenomenon due toelectrical current flowing through a more conductive body of water rather than ground. Our study of the numerical simulation of DCRdata with a three-dimensional forward model demonstrated that the apparent resistivity was reduced as a function of the sea depth andthe distance of measurement site to the shoreline. Furthermore, it was concluded that the marine effects on DCR data (i.e. reductionin apparent resistivity) become nonnegligible as the ratio of half-electrode expansion (AB/2) to the distance to the shoreline is largerthan one. The reduction in apparent resistivity reaches its highest levels as the ratio approaches ten. Our survey conducted along thecoastal line of Northwest Turkey clearly showed that if the marine effects are left untreated, one- or two-dimensional inversion yieldsincorrect resistivities for underlying units and therefore undermines the credibility of survey results. In the paper suggestions are madeto handle such situations.