Hybrid parametric/smooth inversion of electrical resistivity tomography data

TL;DR

This paper introduces a hybrid inversion method for electrical resistivity tomography that combines parametric and smooth strategies, improving boundary resolution and reducing artifacts by leveraging prior information in well-constrained regions.

Contribution

The study develops a novel hybrid inversion algorithm that integrates parametric and smooth models, enhancing subsurface feature resolution over standard methods.

Findings

Hybrid inversion outperforms standard smooth inversion in boundary resolution.

Fewer artifacts are present in hybrid inversion results.

The method is robust across various regularization, initial models, and noise levels.

Abstract

The standard smooth electrical resistivity tomography inversion produces an estimate of subsurface conductivity that has blurred boundaries, damped magnitudes, and often contains inversion artifacts. In many problems the expected conductivity structure is well constrained in some parts of the subsurface, but incorporating prior information in the inversion is not a trivial task. In this study we developed an electrical resistivity tomography inversion algorithm that combines parametric and smooth inversion strategies. In regions where the subsurface is well constrained, the model was parameterized with only a few variables, while the rest of the subsurface was parameterized with voxels. We tested this hybrid inversion strategy on two synthetic models that contained a well constrained highly resistive or conductive near-surface horizontal layer and a target beneath. In each testing scenario, the hybrid inversion improved resolution of feature boundaries and magnitudes and had fewer inversion artifacts than the standard smooth inversion. A sensitivity analysis showed that the hybrid inversion successfully recovered subsurface features when a range of regularization parameters, initial models, and data noise levels were tested. The hybrid inversion strategy can potentially be expanded to a range of applications including marine surveys, permafrost/frozen ground studies, urban geophysics, or anywhere that prior information allows part of the model to be constrained with simple geometric shapes.