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Preprints
https://doi.org/10.5194/egusphere-2025-1398
https://doi.org/10.5194/egusphere-2025-1398
11 Apr 2025
 | 11 Apr 2025
Status: this preprint is open for discussion and under review for Solid Earth (SE).

Quantitative parametrization of fracture networks in Digital Outcrop Models: an optimized workflow

Stefano Casiraghi, Gabriele Benedetti, Daniela Bertacchi, Silvia Mittempergher, Federico Agliardi, Bruno Monopoli, Fabio La Valle, Mattia Martinelli, Francesco Bigoni, Cristian Albertini, and Andrea Bistacchi

Abstract. Mesoscale fractures, with lengths between meters and tens of meters, cannot be effectively characterized in the subsurface, due to limitations of borehole and geophysical datasets. On the other hand, large quantitative structural datasets can be collected on outcrops by combining direct observations and remote sensing (digital outcrop models – DOMs). These data can be used to constrain models of subsurface fracture networks with the outcrop analogue approach.

In this contribution we present a complete and rigorous workflow that leverages digital outcrop models with at least two perpendicular faces, in combination with various kinds of DOMs, to collect large multi-parameter datasets optimized to include all relevant statistical distributions.

Orientation data are collected with a semi-automatic procedure applied to point cloud DOM of the vertical side of the outcrop, resulting in 2D polygonal facets. Fracture sets are defined with a clustering procedure and different orientation distributions are fitted and if possible, tested with proper goodness-of-fit tests.

Fracture traces are digitized on textured surface or orthophoto DOMs. Topological parameters are calculated on the digitized fracture network on horizontal and vertical orthomosaics, also considering relationships with bedding. Trace length and height distributions are characterized with a robust innovative approach, accounting for the censoring bias with survival/reliability analysis. P21 (ratio between total fracture length and sampling area) is measured from traces digitized on the large horizontal outcrop, also allowing for the Representative Elementary Area (REA) to be assessed. Even if the height/length ratio cannot be measured on an outcrop by any means, we apply a realistic assumption and a regression test that avoids making completely theoretical assumptions not supported by data. We discuss the applicability of our workflow on a large top-quality fractured limestone outcrop in the Murge Plateau near Altamura (Puglia, Italy).

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
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Short summary
Traditional methods for investigating the subsurface cannot properly investigate fractures...
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