STRAIGHTFORWARD INVERSION OF VERTICAL ELECTRICAL SOUNDING DATA

A straightforward inversion scheme (SIS) has been developed to interpr et vertical electrical sounding data. This scheme does not require qua si-linearization of the inverse resistivity problem and thereby dispen ses with the iterative process and the necessity of guessing the numbe r of layers and their resistivities and thicknesses. The entire soluti on domain is divided into uniform thickness layers, whose scale must b e judiciously selected for the desired resolution. The apparent resist ivity formula can now be posed as an underdetermined matrix equation w hose minimum norm solution is downward continued to obtain the reflect ion coefficients which, in turn, yield the vertical resistivity distri bution. A recurrence relation has been developed especially for this p urpose. In general, when data are expected to be noisy, a regressed mi nimum norm solution is used. Exhaustive tests of the algorithm have es tablished its numerical efficiency. Results of six typical synthetic m odels, representing diverse geological conditions, as well as results of two field examples are included to demonstrate this claim.