Stepwise and uncertainty-aware 3D structural modelling of the Devonian subsurface in the Eastern Eifel region (Germany)

Three-dimensional structural geological models are widely used to describe subsurface geometry, but their quality strongly depends on how geological complexity and data uncertainty are handled during model construction. In this study, we present a stepwise workflow for building an uncertainty-aware 3D structural model of the Devonian subsurface in the Eastern Eifel region (Germany) using universal co-kriging implemented in the open-source modelling software GemPy.

The modelling approach follows a gradual and controlled strategy. The model construction starts with a simplified stratigraphic framework based on surface geological data. Major Devonian units are added sequentially, followed by the introduction of a main fault structure. Although the modelling steps are applied sequentially, the model is always fully constructed from the input data and can therefore be completely reproduced on this basis. This enables transparent model building and supports future integration into forward uncertainty quantification and sensitivity analysis workflows. This stepwise procedure allows continuous validation of the model and helps to isolate the effect of individual modelling choices, such as unit simplification, fault geometry, and orientation constraints.

Fault modelling is based on a limited number of geometrically constrained fault points and orientations. This setup reproduces a meaningful displacement across the fault while keeping layer surfaces smooth and geologically plausible on both sides. The focus is not on producing a final deterministic model, but on creating a reproducible baseline model that can be extended towards uncertainty quantification.

The resulting 3D structural framework provides a robust basis for future integration of additional geological or geophysical data and for uncertainty analysis using stochastic or ensemble-based approaches. This work demonstrates how stepwise 3D structural modelling with GemPy supports geological consistency while preparing the model for uncertainty-aware subsurface analysis in structurally complex regions.