Low-Cost, Modular 3D Geological Modeling with Python and GemPy: A Regional-Scale Case Study in the Mexico Basin

Abstract Three-dimensional (3D) geological models are essential for understanding complex subsurface systems and supporting groundwater simulation and resource management. However, regional-scale models are often constrained by computational costs, fragmented data, and inaccessible workflows. This study presents a low-cost, modular, and reproducible methodology for constructing regional 3D geological models using open-source tools, including Python scripts with the GemPy and GemGIS libraries. The workflow automates the conversion of GIS-based geological cross-sections into inputs for modeling, reducing manual workload. It was applied to the Mexico Basin, a tectonic-volcanic basin with complex stratigraphy and limited subsurface data. The basin was divided into ten sub-models, each incorporating hydrostratigraphic units and fault geometries. Despite using modest computing resources, the models captured key geological structures and maintained continuity across boundaries. All data and scripts are openly available via Zenodo, promoting transparency and reuse. This approach provides a transferable framework for 3D geological modeling in complex and data-scarce settings.