ANIDIS - L'ingegneria Sismica in Italia, ANIDIS XIX & ASSISi XVII - 2022

Dimensione del carattere:  Piccola  Media  Grande

Best Matching Scenario Earthquake: an alternative paradigm to disaggregation of PHSA

Angela Chiecchio, Roberto Paolucci, Manuela Vanini

Ultima modifica: 2022-09-01


Disaggregation of Probabilistic Seismic Hazard Assessment (PSHA) is commonly employed to estimate the most likely magnitude and distance values (MR) contributing to the hazard at the site of study. Nevertheless, however defined, probabilistic disaggregation techniques are affected by several ambiguities. Among the others, they require the selection of a specific branch of the logic tree used to perform the PSHA, and of a specific structural period, which may be of limited use in some engineering applications, such as for structures with strong participation of higher modes and highly affected by non-linear response, as well as site response analyses and most of the geotechnical engineering applications. In order to overcome some of these drawbacks, this paper introduces a new possibility aiming at estimating a Best Matching Scenario Earthquake (BMSE) defined as the earthquake, specified in terms of (MR), the median spectral ordinates of which best approach a target uniform hazard spectrum (UHS) for the range of structural periods of interest. A more general form of the BMSE can be introduced, i.e., in terms of (M–  e) instead of (M–  e=0), but the paper shows that excellent results can be obtained in most cases along the Italian territory, by limiting the search to e=0. In this article, after highlighting the assumptions behind the method, a few examples of the application of the BMSE with reference to the current seismic hazard model of Italy are shown. Our results show the potential effectiveness of the best matching method that gives in most cases scenarios which are consistent with historical observations. Besides normative implications, such as the selection of input motions for non-linear time history analyses, the BMSE may provide a rationale support for using seismic ground shaking scenarios in a probabilistic framework.  

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