Accounting for Earthquake Sequences in Probabilistic Seismic Hazard Assessment
Description:
Probabilistic seismic hazard analysis (PSHA) generally assumes a time-invariant Poisson process on mainshocks, not accounting for aftershocks. The removal of these events is largely subjective, as it depends on the chosen declustering procedure, and it may also result in an underestimation of the seismic hazard. In fact, recent earthquake sequences proved that aftershocks can significantly contribute to ground shaking.
The present study proposes a new methodology to include earthquake sequences in PSHA. With respect to the procedures used so far, we achieve a good level of consistency and accuracy for different return periods, as well as the generation of synthetic catalogs that exhibit the same features of a real earthquake catalog. We account for aftershocks using the Epidemic-Type Aftershocks Sequence (ETAS) models in order to have a complete and homogenous distribution of events. In particular, we employ the SimplETAS algorithm to create a large number of synthetic catalogs, each spanning 50 years. We associate a plausible seismogenic structure for the epicentral area to each earthquake in the synthetic catalog, and then we calculate the fault-to-site distance. This is critical for assigning a possible ground-shaking value to that earthquake. Eventually, we calculate the probability of exceeding a given threshold of ground shaking intensity as the fraction of catalogs where the intensity is exceeded at least once, without relying on the Poisson distribution.
In this first application, we obtain seismic hazard curves for the next 50 years for four Italian cities spanning from north to south and with different seismicity levels: L’Aquila, Firenze, Reggio Calabria, and Milano. Finally, we compare them and discuss the differences with the official hazard curves from the national model for Italy.
Session: Advancing Time-dependent PSHA and Seismic Risk Assessment: Accounting for Short- to Medium-term Clustering - I
Type: Oral
Date: 4/15/2025
Presentation Time: 11:15 AM (local time)
Presenting Author: Annamaria
Student Presenter: Yes
Invited Presentation:
Poster Number:
Authors
Annamaria Pane Presenting Author Corresponding Author a.pane@ssmeridionale.it Scuola Superiore Meridionale |
Francesco Visini francesco.visini@ingv.it National Institute of Geophysics and Volcanology |
Warner Marzocchi warner.marzocchi@unina.it University of Naples Federico II |
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Accounting for Earthquake Sequences in Probabilistic Seismic Hazard Assessment
Session
Advancing Time-dependent PSHA and Seismic Risk Assessment: Accounting for Short- to Medium-term Clustering