Uncertainty analysis for seismic hazard in Northern and Central Italy
Main Article Content
Abstract
In this study we examine uncertainty and parametric sensitivity of Peak Ground Acceleration (PGA) and 1-Hz
Spectral Acceleration (1-Hz SA) in probabilistic seismic hazard maps (10% probability of exceedance in 50
years) of Northern and Central Italy. The uncertainty in hazard is estimated using a Monte Carlo approach to
randomly sample a logic tree that has three input-variables branch points representing alternative values for bvalue,
maximum magnitude (Mmax) and attenuation relationships. Uncertainty is expressed in terms of 95% confidence
band and Coefficient Of Variation (COV). The overall variability of ground motions and their sensitivity
to each parameter of the logic tree are investigated. The largest values of the overall 95% confidence band
are around 0.15 g for PGA in the Friuli and Northern Apennines regions and around 0.35 g for 1-Hz SA in the
Central Apennines. The sensitivity analysis shows that the largest contributor to seismic hazard variability is uncertainty
in the choice of ground-motion attenuation relationships, especially in the Friuli Region (?0.10 g) for
PGA and in the Friuli and Central Apennines regions (?0.15 g) for 1-Hz SA. This is followed by the variability
of the b-value: its main contribution is evident in the Friuli and Central Apennines regions for both 1-Hz SA
(?0.15 g) and PGA (?0.10 g). We observe that the contribution of Mmax to seismic hazard variability is negligible,
at least for 10% exceedance in 50-years hazard. The overall COV map for PGA shows that the uncertainty
in the hazard is larger in the Friuli and Northern Apennine regions, around 20-30%, than the Central Apennines
and Northwestern Italy, around 10-20%. The overall uncertainty is larger for the 1-Hz SA map and reaches 50-
60% in the Central Apennines and Western Alps.
Spectral Acceleration (1-Hz SA) in probabilistic seismic hazard maps (10% probability of exceedance in 50
years) of Northern and Central Italy. The uncertainty in hazard is estimated using a Monte Carlo approach to
randomly sample a logic tree that has three input-variables branch points representing alternative values for bvalue,
maximum magnitude (Mmax) and attenuation relationships. Uncertainty is expressed in terms of 95% confidence
band and Coefficient Of Variation (COV). The overall variability of ground motions and their sensitivity
to each parameter of the logic tree are investigated. The largest values of the overall 95% confidence band
are around 0.15 g for PGA in the Friuli and Northern Apennines regions and around 0.35 g for 1-Hz SA in the
Central Apennines. The sensitivity analysis shows that the largest contributor to seismic hazard variability is uncertainty
in the choice of ground-motion attenuation relationships, especially in the Friuli Region (?0.10 g) for
PGA and in the Friuli and Central Apennines regions (?0.15 g) for 1-Hz SA. This is followed by the variability
of the b-value: its main contribution is evident in the Friuli and Central Apennines regions for both 1-Hz SA
(?0.15 g) and PGA (?0.10 g). We observe that the contribution of Mmax to seismic hazard variability is negligible,
at least for 10% exceedance in 50-years hazard. The overall COV map for PGA shows that the uncertainty
in the hazard is larger in the Friuli and Northern Apennine regions, around 20-30%, than the Central Apennines
and Northwestern Italy, around 10-20%. The overall uncertainty is larger for the 1-Hz SA map and reaches 50-
60% in the Central Apennines and Western Alps.
Article Details
How to Cite
1.
Lombardi AM, Akinci A, Malagnini L, Mueller CS. Uncertainty analysis for seismic hazard in Northern and Central Italy. Ann. Geophys. [Internet]. 2005Dec.25 [cited 2023Dec.2];48(6). Available from: https://www.annalsofgeophysics.eu/index.php/annals/article/view/3239
Issue
Section
OLD
Open-Access License
No Permission Required
Istituto Nazionale di Geofisica e Vulcanologia applies the Creative Commons Attribution License (CCAL) to all works we publish.
Under the CCAL, authors retain ownership of the copyright for their article, but authors allow anyone to download, reuse, reprint, modify, distribute, so long as the original authors and source are cited. No permission is required from the authors or the publishers.
In most cases, appropriate attribution can be provided by simply citing the original article.
If the item you plan to reuse is not part of a published article (e.g., a featured issue image), then please indicate the originator of the work, and the volume, issue, and date of the journal in which the item appeared. For any reuse or redistribution of a work, you must also make clear the license terms under which the work was published.
This broad license was developed to facilitate open access to, and free use of, original works of all types. Applying this standard license to your own work will ensure your right to make your work freely and openly available. For queries about the license, please contact ann.geophys@ingv.it.