Summary

Simulated earthquake ground motions are useful in engineering applications, from developing ground motion models to improving seismic hazard assessments and performing structural response analyses. Various simulation approaches—including stochastic, physics-based, and hybrid methods—offer unique strengths depending on the intended application. Broader use depends not only on producing realistic waveforms, but also on validating simulations for their intended applications and providing the evidence, uncertainty information, and guidance needed to use them responsibly.

Over the past two decades, major advances have refined ground motion simulations, and coordinated efforts led by the Southern California Earthquake Center (SCEC) have helped bridge the gap between simulation developers and engineering practitioners. Building on this foundation, the Statewide California Earthquake Center and the U.S. Geological Survey convened the 2026 Workshop on Earthquake Ground Motion Simulation Validation and Utilization (GM-SVU) for Engineering Applications during the 13th National Conference on Earthquake Engineering (13NCEE) in Portland, Oregon. The workshop brought together researchers and professionals from earthquake science and engineering to examine two closely related challenges: (1) validating simulated ground motions for use in probabilistic seismic hazard analyses and (2) advancing their broader utilization through engineering guidance and best practices. These efforts are critical for building confidence in simulations and supporting their effective integration into seismic hazard analysis, engineering design, and risk mitigation. The discussions emphasized that “application-ready” cannot be defined by a single universal validation test: PSHA and engineering response analyses use simulations differently and therefore require different evidence.

The workshop featured invited presentations, community discussions, and a panel session on advances in ground motion simulation validation, SCEC simulation capabilities, engineering applications, and future GM-SVU priorities. Building on decades of community earthquake modeling and validated simulation resources, participants examined scientific, engineering, and community priorities needed to advance the validation, accessibility, and broader utilization of ground motion simulations. Panel recommendations focused on matching validation evidence to the intended use, evaluating the complete model configuration and its uncertainties, and delivering simulations with the metadata, model inputs, validation information, and practical guidance needed by downstream users.

A complementary community survey provided additional perspectives from researchers and practitioners to help guide future GM-SVU activities. The survey reinforced the need for engineering guidance, application-specific validation, uncertainty communication, training, and shared community resources.

Key Outcomes

The workshop presentations, community discussions, panel session, and complementary community clarified the scientific, engineering, and community requirements for the validation and utilization of ground motion simulations.

1. Clarified how validation requirements differ by application: Building on more than a decade of ground motion simulation validation research summarized by Rezaeian et al. (2024), the workshop reviewed validation approaches for both hazard analyses and structural response applications and traced the evolution of qualitative waveform comparisons to application-specific validation metrics. The panel discussion sharpened this distinction: PSHA requires region-specific validation of the ground-motion distribution and its uncertainties, while some RHA applications may rely on broader validation of the simulation method combined with scenario-appropriate motions and evidence of reliable engineering performance. Validation must also cover the complete model configuration and assumptions used in the intended application.
2. Connected SCEC’s simulation capabilities with validation and user needs: The workshop highlighted current and emerging SCEC capabilities for producing, validating, and distributing ground motion simulations through the CyberShake and Broadband platforms. Presentations demonstrated how community simulation resources, validated datasets, open-source software, and standardized validation tools can fill critical data gaps and expand access to large-scale simulation products. Participants also examined future directions for SCEC’s simulation ecosystem, including AI-enabled workflows for simulation acceleration, uncertainty quantification, informed interpolation, and data analysis; next-generation velocity and site-response models; and cyberinfrastructure connecting earthquake source characterization, wave propagation, validation, and structural response. Discussions emphasized evaluating these components as an integrated model configuration, because validation performed with one combination of source, rupture, velocity, or site assumptions may not transfer to another. Participants also identified the need for simulation products that include standardized metadata, model inputs, validation information, and sufficient provenance for users to determine where and how the simulations can be applied.
3. Identified requirements and existing pathways for engineering use: Presentations demonstrated applications in seismic hazard analysis, structural and geotechnical engineering, and performance-based design, including international efforts to develop standards and guidelines for validating, disseminating, and utilizing simulated ground motions; the SCEC Utilization of Ground Motion Simulations (UGMS) initiative; and nonlinear response history analysis and collapse-risk assessment. The panel also noted that ASCE 7-22 already allows simulated ground motions to supplement recorded motions in nonlinear response history analysis when suitable records are unavailable. Broader use will require application-ready resources containing raw waveforms, standardized metadata, model inputs, validation and uncertainty information, and practical selection guidance, supported by case histories, practitioner-facing tools, and engagement with engineers, building officials, and standards organizations.
4. Documented community priorities and barriers to broader use: To complement the workshop, SCEC conducted a community survey that received 26 responses from researchers and practitioners spanning ground motion simulation, validation, hazard analysis, and engineering practice. Engineering Guidance and Best Practices was the highest priority for the next 3–5 years (15 selections), followed by Site Response and Basin Effects (12), Ground Motion Validation Methods (8), and Velocity Model Uncertainty (8). The leading barriers were insufficient validation evidence and the lack of engineering guidance or standards, each identified by 12 respondents, followed by limited training or familiarity, identified by 11. These findings indicate that broader adoption requires not only scientific capability, but also by the guidance, training, and shared resources needed to apply simulations responsibly. See Community Survey Results below for more details.
5. Connected the communities needed to advance GM-SVU: The workshop brought together 78 participants representing universities, consulting firms, engineering companies, government agencies, research laboratories, professional organizations, and industry from the United States and 10 additional countries. Participants spanned 10 primary discipline areas, including simulation developers, validation researchers, engineering seismologists, hazard and risk analysts, structural, geotechnical, and civil engineers, and building code and standards professionals. The workshop connected expertise across the full simulation-to-application workflow: producing and documenting simulations, evaluating their performance and uncertainty, defining application requirements, and translating validated products into engineering tools, guidance, and standards.

References

• Rezaeian, S, JP Stewart, CA Goulet, N Luco (2024). Findings from a decade of ground motion simulation validation research and a path forward, Earthquake Spectra, 40(1), 346-378.