In-Depth Analyses of HEM, LOTEM, and Semi-AEM Resolution Capabilities

Different electromagnetic (EM) techniques have distinct resolutions for the exploration of natural resources. Integrating independent information from different EM datasets in a joint inversion results in a more precise and reliable resistivity model. To conduct an efficient joint inversion, it is crucial to understand the resolution characteristics of each EM technique and configuration. To enhance the interpretation using 1-D joint inversion of multiple EM datasets in a former mining area in eastern Thuringia (Germany), we developed a novel workflow for systematic resolution studies. Rather than focusing on limited resistivity models, our approach provides a broader perspective on the resolution characteristics of specific EM methods. The workflow is applied to helicopter-borne EM (HEM), semi-airborne EM (Semi-AEM), and long-offset transient EM datasets. Resolution studies reveal not only the advantages and limitations of each method but also demonstrate scenarios where joint inversion benefits. These insights are useful to optimally design multimethod applications. A synthetic 1-D joint inversion example successfully reconstructs the true model, while each individual method fails. This example demonstrates the added value of our presented resolution study workflow with respect to experimental design and acquiring optimal data in terms of resolution capabilities. We provide a toolkit for resolution analysis that serves as a roadmap for multimethod studies. Subsequently, we demonstrate that the accurate determination of shallow layers improves the resolution for deep targets. This is significant for designing deep exploration prospects. In the last step, our novel triple-method joint inversion scheme is validated through the application of field data.