Reconciling the Geological Framework (GFM) with the Community Fault Model (CFM)
Laurent G. Montesi, Andreas Plesch, & John H. ShawSubmitted September 7, 2025, SCEC Contribution #14833, 2025 SCEC Annual Meeting Poster #TBD
The Geological Framework (GFM) describes California as a collection of lithotectonic blocks, each with an ascribed geological column through the crust. This model intends to provide sufficient lithological information to assign material properties, such as rheological parameters, throughout the lithosphere, with the ultimate objective of informing large-scale models of fault loading and lithosphere evolution. To achieve that objective, additional material properties must also be ascribed to the interfaces between blocks. While several of these boundaries are linked to aeromagnetic anomalies and other geological contacts, some correspond to known faults. Thus, there is an opportunity to link the GFM block boundaries to the Community Fault Model (CFM) as a step towards an integrated model of the region.
We present here preliminary results, focusing on the development of Python modules allowing this model to be built semi-automatically. The purpose of these modules is to enable quick model rebuilding when the CFM is updated, or when information is available from an alternative fault database. We want the utilities to be open-source and require no specific commercial license. This project required defining basic operations, including translating tsurfs to a Python CFM class, extracting the edges of these surfaces for subsequent mesh building, building a new surface between these meshes to fill gaps between mapped faults, as the GFM blocks must be watertight, cutting CFM surfaces at the intersection between blocks, handling non-fault surfaces in the same framework, and extending surfaces at depth under a series of assumptions. Moreover, we are developing a logic tree describing the GFM blocks, the surfaces bounding them, and the operations necessary to construct their boundaries. These facilities will help generate alternative versions of the GFM based on geological choices and extend that model to the entirety of California.
In parallel, we updated the existing GFM 1.0 volumetric mesh to conform to CFM 7.0 where bounding faults were improved from CFM 5.3, by building a GOCAD structural model typically used in reservoir characterisation. This process includes selecting fault and non-fault boundaries, merging and extending faults, defining fault-to-fault relationships, and adding "horizons" (topography, seismogenic depth, Moho, LAB). The resulting, well defined structural model is used to resample region bounding surfaces for regularized 2D and 3D meshing.
Citation
Montesi, L. G., Plesch, A., & Shaw, J. H. (2025, 09). Reconciling the Geological Framework (GFM) with the Community Fault Model (CFM). Poster Presentation at 2025 SCEC Annual Meeting.
Related Projects & Working Groups
Community Earth Models (CEM)
