Development of novel velocity–resistivity relationships for granitic terrains based on complex collocated geotomographic modeling and supervised statistical analysis

The significance of velocity-resistivity relationships has been utilized in various geologic terrains and under different conditions. The approach is yet to be exploited in tropical granitic terrains, with no definitive empirical relationships being developed. The empirical relationships are critical for rapidly delineating subsurface petrophysical, geomechanical, hydrogeological, and soil-rock features. As a result, a novel approach has been used in this study to develop velocity-resistivity relationships for tropical granitic environments, combining complex collocated velocity (Vp) and resistivity (ρ) models with simple linear regression analysis. The granitic terrain of Penang Island, Malaysia, was chosen as the study area. The geotomographic results delineated three layers, which include the residual soils (topsoil and completely weathered granite), highly to relatively weathered granitic unit (including fractures), and integral/fresh granitic bedrock. Due to the complexity, ruggedness, and varying weathering and fracturing conditions of the subsurface lithologic units in tropical regions, the supervised regression modeling successfully developed a unified and other three specific velocity–resistivity empirical relations for the lithologic units. The derived velocity-resistivity empirical relations have high practical prediction accuracies to predict Vp data. The predicted Vp data and models from the velocity-resistivity relations had good lithological and structural correlations with their observed models. The overall performance of the results indicated that the velocity-resistivity empirical relations could delineate the subsurface geologic variabilities distinctively because they are resistivity-dependent. Hence, the developed comprehensive methodological and SLR workflows and the velocity-resistivity empirical relations were posited for use in granitic terrains with similar geology to the study area, especially in areas with shallow overburden.

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Opracowanie rekordu ze środków MNiSW, umowa nr POPUL/SP/0154/2024/02 w ramach programu "Społeczna odpowiedzialność nauki II" - moduł: Popularyzacja nauki (2025).