W dniu 4.11.2025 miało miejsce spotkanie Zakładu Sejsmologii, którego głównym punktem były seminaria poprowadzone przez Jose Augusto Fonsec.
Tytuł seminariów: „Probabilistic Seismic Hazard Analysis for Northeast Brazil”. Poniżej krótkie streszczenie zaprezentowanej pracy naukowej, przygotowane przez samego autora:
„Stable continental regions present particular challenges for seismic hazard assessment due to their low seismicity, sparse instrumental records, and poorly defined active faults. Yet, the potential impact of moderate earthquakes on vulnerable structures in these regions underscores the importance of robust hazard estimation. This study focused on Northeast Brazil, the most seismically active sector of the South American stable interior, where past earthquakes have caused structural damage and social impacts. A regional Probabilistic Seismic Hazard Analysis (PSHA) was carried out based on an updated earthquake catalog and newly delineated seismic source zones. The analysis incorporated a probabilistic treatment of source, path, and site effects, with particular attention given to the statistical characterization of the magnitude distribution. In one of the seismic zones, the classical Gutenberg–Richter relationship was rejected, and a nonparametric adaptive kernel estimator was applied instead, resulting in a more accurate representation of local seismicity. The results indicate that although most of Northeast Brazil exhibits low expected ground motion levels (PGA < 0.01 g for 10% probability of exceedance in 50 years), certain areas show significantly higher hazard values, reaching PGA levels between 0.12 g and 0.26 g. Uniform hazard spectra for critical sites revealed peak spectral accelerations up to 0.41 g, remaining relatively high over a broad range of structural periods. These findings suggest that, while most of the region complies with current Brazilian seismic design standards, localized areas may require revised design considerations.”
