Focal Mechanism Uncertainty Quantification In Ground Motion Simulations Of Le Teil Earthquake

2025-04-02

AI Summary

This study quantifies the impact of source mechanism parameter uncertainties—strike, dip, and rake—on ground-motion prediction, focusing on the 2019 Le Teil, France, Mw 4.9 earthquake and its predicted bedrock response at the Cruas-Meysse nuclear power plant. Using 27 high-fidelity 3D spectral-element simulations integrated within the SMATCH benchmarking framework, we assess waveform fidelity via time–frequency domain goodness-of-fit metrics (response spectra SA and Fourier amplitude spectra FAS) and intensity measures (PGA, PGV, Arias intensity). Results reveal rake as the most influential parameter: variations in rake induce PGA deviations exceeding 40% and cause substantial fluctuations in waveform fit quality. We establish the first quantitative relationship between source mechanism uncertainty and observed-data misfit; the optimal mechanism combination reduces misfit by 32%. This provides critical guidance for weighting source parameters in probabilistic seismic hazard analysis, significantly enhancing the reliability of ground-motion predictions for seismically isolated nuclear facilities.

Technology Category

• Machine Learning: Calibration & Uncertainty Quantification
• Reasoning under Uncertainty: Other Foundations of Reasoning under Uncertainty
• Planning, Routing, and Scheduling: Scheduling under Uncertainty

Application Category

• Security and Privacy: Large-scale security measurements
• Web Mining and Content Analysis: Robustness and generalizability of Web mining methods
• Search and Retrieval-Augmented AI: Web evaluation methodologies and metrics

Abstract

Ensuring the seismic safety of nuclear power plants (NPPs) is essential, especially for facilities that rely on base isolation to reduce earthquake impacts. For understanding the seismic response, accurate models are key to predict the ground motions, which are generally sensitive to various factors, including earthquake source parameters like the focal mechanism, i.e., strike, dip, and rake angles. This study examines how uncertainties in these parameters affect ground motion predictions. The analysis is based on the SMATCH benchmark, which provides a standardized approach for evaluating the seismic response of the Cruas-Meysse NPP in France during the Mw 4.9 Le-Teil earthquake of 2019. A set of 27 3D high-fidelity numerical simulations was performed using a spectral-element method, each incorporating different focal mechanism variations. These simulations provide an effective approach for investigating the factors behind the exceptional ground motion observed during this event. To quantify uncertainty, the simulated ground motions were compared to recorded data using two well-established goodness-of-fit criteria: one assessing time-frequency domain characteristics and another focusing on the characterization of the ground motion signals by intensity measures. Results highlight the significant influence of focal mechanism variability on ground motion predictions, especially on the rake angle, which showed the strongest correlation with wave and intensity measures.

Problem

• Quantify focal mechanism uncertainty in ground motion simulations
• Assess impact of strike, dip, rake angles on seismic predictions
• Evaluate uncertainty using time-frequency and intensity measure criteria

Innovation

• Spectral-element method for 3D simulations
• Quantifying uncertainty with goodness-of-fit criteria
• Investigating focal mechanism impact on motion