Schlumberger resistivity and electromagnetic sounding data have been obtained over prehistoric Lake Bonneville sediments near Delta, Utah. Inverse interpretation of these data illustrates that vertical electric sounding with the Schlumberger array is superior, for this environment, to electromagnetic sounding with either a vertical magnetic dipole or a horizontal magnetic dipole. Combined parametric and geometric electromagnetic sounding using 84 data points is inferior to Schlumberger sounding using 21 data points. However, superiority in these contexts pertains to parameter resolution. The earth models obtained with all three soundings are virtually identical within the limits of resolution.
The importance of percent parameter standard deviations, parameter correlations, and least–squares residuals are all illustrated for a field example in this manuscript. Reparameterization in terms of the Dar Zarrouk parameters S and T reduces the parameter correlations as expected. A generalization of reparameterization beyond the Dar Zarrouk parameters is suggested.