Joint inversion of VES and TEM data; succes and faillure

The simultaneous use of Vertical Electric Sounding (VES) and Transient Electromagnetic (TEM) can reduce the ambiguity in the 1-D interpretation of the data of the individual methods. This can best be realised by a joint inversion of both data sets. (Jupp and Vozoff, 1975; Raiche et al., 1985). In Netherlands VES, using a Schlumberger electrode configuration, is commonly used for shallow hydrogeological applications. The succession of sand and clay layers and the depth of the water level is the target of such measurements. Since the development of fast switching instruments for Transient Electromagnetic Sounding, it becomes feasible to use TEM as well for this purpose. A sensitivity analysis for different common subsurface conditions in Netherlands showed that the joint inversion of YES and TEM data would indeed reduce the ambiguity.