SEM: Shallow Earth Materials (TAG)

William A. Griffith, Alexis K. Ault, Thomas K. Rockwell, Brady R. Cox, Eileen L. Evans, Yihe Huang, Kathryn Materna, Alba M. Rodriguez Padilla, & Hiroki Sone

Submitted August 30, 2026, SCEC Contribution #15091, 2026 SCEC Annual Meeting Poster #TBD

Shallow Earth Materials (SEM), encompassing the upper ~3 km of rock, sediment, and soil, strongly influence earthquake rupture propagation, interseismic creep, near-fault deformation, seismic site response, and the geologic record of past earthquakes. Despite their importance, these materials remain among the least constrained components of the earthquake system, occupying a disciplinary gap between earthquake geology, geodesy, geophysics, geomechanics, geotechnical engineering, and ground-motion modeling. The newly funded SCEC SEM Technical Activity Group (TAG) was developed in response to a November 2025 community workshop on earthquake rupture and creep in shallow earth materials that brought together 37 participants, including more than 20 early-career researchers, for field observations along the southern San Andreas Fault and a day of interdisciplinary presentations and discussion.

Workshop participants identified several key challenges: limited understanding of how shallow material properties control the transition between seismic slip and creep; uncertainty in the role of the geotechnical layer in modulating surface deformation and ground motions; incompatible datasets, terminology, and metadata standards across disciplines; and a need for sustained observational infrastructure and coordinated field studies. A central outcome was broad consensus that closer integration among earthquake scientists and engineers is needed to connect observations of shallow fault-zone materials with Community Earth Models (CEMs), dynamic rupture simulations, and hazard assessment.

The SEM TAG builds on this momentum by establishing a collaborative framework focused on cross-disciplinary training, community building, and improved characterization of shallow fault-zone materials. Year 1 activities include a virtual planning workshop to define priority scientific questions, identify key field sites and CEM data gaps. The cornerstone activity will be the inaugural SEM School, a week-long research incubator that combines tutorials and training on multidisciplinary data collection and processing techniques leading to a collaborative research project. Through these activities, the SEM TAG aims to develop a trained interdisciplinary workforce, improve representation of shallow materials in community models, and strengthen connections between fundamental earthquake science and engineering applications. Please be on the lookout for applications for the inaugural SEM school!

Key Words
shallow earth materials, earthquake rupture, creep, off fault deformation, geotechnical layer, site response characterization

Citation
Griffith, W. A., Ault, A. K., Rockwell, T. K., Cox, B. R., Evans, E. L., Huang, Y., Materna, K., Rodriguez Padilla, A. M., & Sone, H. (2026, 08). SEM: Shallow Earth Materials (TAG). Poster Presentation at 2026 SCEC Annual Meeting.

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)