Statistical comparison of Schlumberger arrays using randomized complete block design

Abstract

In this study, statistical comparison of the resistivity data acquired using vertical electrical sounding (VES) technique with three arrays (conventional Schlumberger array, Hummel array and half-Hummel array) was performed. The objective is to assess the efficacy of the Hummel and half-Hummel arrays of VES as alternative arrays to the conventional Schlumberger array at areas with limited space for acquisition during groundwater exploration activities. A total of fifteen (15) VES data were acquired for the three arrays at five locations within Phase II of Federal University Oye-Ekiti, southwestern, Nigeria. The electrode spacing (AB/2) varies from 1 to 65 m during the acquisition. The raw VES data were subjected to statistical analysis to compare the three arrays. Randomized complete block design (RCBD) was used to establish if one array could be a perfect or near perfect substitution for other arrays. The responses obtained for all the arrays analysed are statistically the same at some locations which means measurements could either be taken using any of the three arrays. However, responses for the three arrays are different at a location which shows the three arrays are independent in this location. Pairwise comparison analysis at this location shows the difference in the three arrays. We therefore generated acceptance and rejection map of the study area which could be used as a guide prior to any geophysical data acquisition.