Public Thesis Defense of Mahsa ONVANI - IMMC
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Earthquake ground motion in Belgium: Contribution to a high-quality database, Analysis of anelastic attenuation, and evaluation of ground motion models
Tuesday May 5th, 2026 - 3:30pm - Meridian room, Royal Observatory of Belgium Avenue Circulaire 3, 1180 Brussels
This thesis investigates earthquake ground motion in Belgium, with the objective of improving seismic hazard assessment in a low-to-moderate seismicity region. The work is based on three main contributions: the development of a high-quality ground-motion database (BELSHAKE), the analysis of high-frequency attenuation using the kappa (κ) parameter, and the evaluation of ground-motion models (GMMs).
The BELSHAKE database provides a systematically processed and quality-controlled dataset of weak to moderate earthquake recordings, enabling consistent analysis of ground-motion characteristics. Using this dataset, high-frequency attenuation is quantified through κ, leading to the estimation of site-specific (κ₀) and regional attenuation parameter (κ_r), and revealing spatial variability linked to Belgian crustal structure.
Finally, a wide range of GMMs is evaluated against the BELSHAKE data using multiple statistical measures. The results highlight the importance of regional calibration, as many models developed in high-seismicity regions tend to overestimate ground motions for small events. A subset of models is identified that best represents observed ground motion in Belgium.
Together, these contributions provide a consistent framework and essential input for improving seismic hazard assessment and reducing uncertainty in Belgium.
Jury members
Dr. Kris Vanneste (Royal Observatory of Belgium) (Supervisor)
Prof. João Saraiva Esteves Pacheco de Almeida (UCLouvain) (Supervisor)
Prof. Paul Fisette (UCLouvain) (Chairperson)
Prof. Hadrien Rattez (UCLouvain) (Secretary)
Dr. Thierry Camelbeeck (Royal Observatory of Belgium)
Dr. Paola Traversa Electricite de France (EDF)
Dr. Helen Crowley Global Earthquake Model (GEM)
Prof. Hervé Degée (Hasselt university)