California Statewide Geologic Framework and Community Thermal Models (GFM/CTM) Workshop Report

Michael E. Oskin, Andrew V. Zuza, Terry Lee, Laurent G. Montesi, Oliver S. Boyd, & Yuehua Zeng

Published November 14, 2025, SCEC Contribution #15053

Developing Community Earth Models (CEMs) constitutes a major Statewide California Earthquake Center (SCEC) activity. With the expansion of SCEC Statewide, there is an urgent need to extend the geographical scope of these models as well. Among the CEM components, the Geological Framework Model (GFM, Oskin et al., 2017) and Community Thermal Model (CTM, Thatcher et al., 2020) are foundational products on which other models like the Community Rheology Model (CRM, Hearn et al., 2020) are built and constitute a crucial framework for the interpretation of velocity, geodetic, and stress models and measurements. With this in mind, we convened a joint Geological Framework (GFM) and Community Thermal Model (CTM) workshop at UC Davis, CA, to identify critical datasets and organize the community of volunteers working to update and extend these models to the entirety of California. The choice of UC Davis as a venue was motivated by its central location in Northern California, with easy access from major institutions with geologists actively studying Northern California geology, such as those in San Francisco, CA, Sacramento, CA, and Reno, NV. The SCEC5 geological framework is a model of the distribution of major lithotectonic provinces in Southern California, largely inherited from pre-San Andreas convergent-margin processes (Crouch & Suppe, 1993). The framework for Northern California is broadly similar to that of Southern California, but with a greater contribution of accretionary tectonics to constructing the crust of the west-facing continental margin (Day et al., 1985; Ernst, 2017). Workshop discussion of the GFM centered on (1) extending existing lithotectonic provinces and defining additional lithotectonic provinces for Northern California, (2) incorporating major three-dimensional features such as dipping boundaries, deep sedimentary basins, and sub-province scale variations in crustal structure, and (3) developing upper mantle models that are consistent with tomographic and thermal constraints. Contributions were solicited from allied efforts at the USGS (San Francisco Bay Area 3-D model— Hirakawa & Aagaard, 2022, and National Crustal Model— Boyd, 2019a) and CGS (3-D geological modeling effort).

Over 50 years of thermal modeling developments accompanied by continuing accumulation of observations and improved computational power allow higher resolution and better-constrained temperature estimation of the continental crust. Further, several thermal models have been developed in the United States, ranging from national to regional models, and comprise the entirety of the Pacific-North American plate transform boundary in California (Boyd, 2019b; Lee et al., 2024; Shinevar et al., 2018; Thatcher et al., 2020). For this workshop, community members were invited to discuss and assess available observations and constraints, diverse modeling techniques, existing CTMs, and their relevance for evaluating seismicity and related applications. The current state of the CTM was discussed, as well as ways that the existing suite of CTMs can be accessed. Community participation in and discussion of CTM development seeded new ideas and suggestions for future CTM updates and generated feedback on the role of the CTM in relation to the broader Community Earth Models (CEM) framework. The workshop was organized by eight PIs, including two early-career PhD students.

Citation
Oskin, M. E., Zuza, A. V., Lee, T., Montesi, L. G., Boyd, O. S., & Zeng, Y. (2025). California Statewide Geologic Framework and Community Thermal Models (GFM/CTM) Workshop Report. , : Statewide California Earthquake Center. https://www.scec.org/events/2025-scec-gfm-ctm-workshop/