A Walsh sequency filtration method for integrating the resistivity log and sounding data

Abstract

The integration of resistivity logs and soundings data, essential for resolving the problems of ambiguity and nonuniqueness ubiquitous in the interpretation of electrical resistivity soundings, is generally difficult because the former contain far more details than can be retrieved from the latter. As logarithmic scaling linearizes the behavior of apparent resistivity values and resistivity transform functions, and as the Walsh functions realistically mimic the resistivity logs, the strategy proposed here is to use the resistivity‐stratigraphy schematized from Walsh‐filtration of logarithmically scaled logs‐profile as input model for sounding interpretation. The efficiency of this strategy is demonstrated here with a practical example from groundwater exploration. The synthetic sounding curve based on 29 layers manually schematized from the observed linearly scaled logs‐profile could be modeled by 8 layers, whereas that computed from 14 layers schematized from sequency‐filteration of the logarithmically scaled logs‐profile closely matched the observed sounding curve from a nearby location.