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Chioccarelli, Eugenio
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- PublicationRestrictedThe Central Italy Seismic Sequence between August and December 2016: Analysis of Strong‐Motion Observations(2017)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;Since August 2016, central Italy has been struck by one of the most important seismic sequences ever recorded in the country. In this study, a strong-motion data set, consisting of nearly 10,000 waveforms, has been analyzed to gather insights about the main features of ground motion, in terms of regional vari- ability, shaking intensity, and near-source effects. In particular, the shake maps from the three main events in the sequence have been calculated to evaluate the distribution of shaking at a regional scale, and a residual analysis has been performed, aimed at interpreting the strong-motion parameters as func- tions of source distance, azimuth, and local site conditions. Par- ticular attention has been dedicated to near-source effects (i.e., hanging wall/footwall, forward-directivity, or fling-step ef- fects). Finally, ground-motion intensities in the near-source area have been discussed with respect to the values used for structural design. In general, the areas of maximum shaking appear to reflect, primarily, rupture complexity on the finite faults. Large ground-motion variability is observed along the Apennine direction (northwest–southeast) that can be attributed to source-directivity effects, especially evident in the case of small-magnitude aftershocks. Amplifications are observed in correspondence to intramountain basins, fluvial valleys, and the loose deposits along the Adriatic coast. Near-source ground motions exhibit hanging-wall effects, forward-directivity pulses, and permanent displacement.785 72 - PublicationOpen AccessItalian Map of Design Earthquakes from Multimodal Disaggregation Distributions: Preliminary Results.(2010-08-30)
; ; ; ;Chioccarelli, E.; Dipartimento di Ingegneria Strutturale, Università degli Studi di Napoli, Federico ;Iervolino, I.; Dipartimento di Ingegneria Strutturale, Università degli Studi di Napoli, Federico ;Convertito, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;; Probabilistic seismic hazard analysis allows to calculate the mean annual rate of exceedance of ground motion intensity measures given the seismic sources the site of interest is subjected to. This piece of information may be used to define the design seismic action on structures. Moreover, through disaggregation of seismic hazard, it is possible to identify the earthquake giving the largest contribution to the hazard related to a specific IM value. Such an information may also be of useful to engineers in better defining the seismic treat for the structure of interest (e.g., in record selection for nonlinear seismic structural analysis). On the other hand, disaggregation results change with the spectral ordinate and return period, and more than a single event may dominate the hazard, especially if multiple sources affect the hazard at the site. In this work disaggregation for structural periods equal to 0 sec and 1.0 sec is presented for Italy, with reference to the hazard with a 475 year return period. It will be discussed how for the most of Italian sites more than a design earthquake exist, because of the modelling of seismic sources.135 205 - PublicationRestrictedEngineering design earthquakes from multimodal hazard disaggregation(2011)
; ; ; ;Iervolino, I. ;Chioccarelli, E. ;Convertito, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ; ;To define reference structural actions, engineers practicing earthquake resistant design are required by codes to account for ground motion likely to threaten the site of interest and also for pertinent seismic source features. In most of the cases, while the former issue is addressed assigning a mandatory design response spectrum, the latter is left unsolved. However, in the case that the design spectrum is derived from probabilistic seismic hazard analysis, disaggregation may be helpful, allowing to identify the earthquakes having the largest contribution to the hazard for the spectral ordinates of interest. Such information may also be useful to engineers in better defining the design scenario for the structure, e.g., in record selection for nonlinear seismic structural analysis. On the other hand, disaggregation results change with the spectral ordinate and return period, and more than a single event may dominate the hazard, especially if multiple sources affect the hazard at the site. This work discusses identification of engineering design earthquakes referring, as an example, to the Italian case. The considered hazard refers to the exceedance of peak ground acceleration and 1s spectral acceleration with four return periods between 50 and 2475 year. It is discussed how, for most of the Italian sites, more than a design earthquake exists, because of the modeling of seismic sources. Furthermore, it is explained how and why these change with the limit state and the dynamic properties of the structure. Finally, it is illustrated how these concepts may be easily included in engineering practice complementing design hazard maps and effectively enhancing definition of design seismic actions with relatively small effort.151 23 - PublicationOpen AccessSequence-based hazard analysis for Italy considering a grid seismic source model(2021)
; ; ; ; ; ; ; Earthquakes are usually clustered in both time and space and, within each cluster, the event ofhighest magnitude is conventionally identified as the mainshock, while the foreshocks and theaftershocks are the events that occur before and after it, respectively. Mainshocks are theearthquakes considered in the classical formulation of the probabilistic seismic hazard analysis(PSHA), where the contribution of foreshocks and aftershocks is usually neglected. In fact, ithas been shown that it is possible to rigorously, within the hypotheses of the model, account forthe effect of mainshock-aftershocks sequences by means of the sequence-based PSHA (i.e.,SPSHA). SPSHA extends the usability of the homogeneous Poisson process, adopted formainshocks within PSHA, to also describe the occurrence of clusters maintaining the same inputdata of PSHA; i.e., the seismic rates derived by a declustered catalog. The aftershocks’occurrences are accounted for by means of conditional non-homogeneous Poisson processesbased on the modified Omori law. The seismic source model for Italy has been recentlyinvestigated, and the objective of the study herein presented is to include and evaluate the effectof aftershocks, by means of SPSHA, based on a new grid model. In the paper, the results of PSHAand SPSHA are compared, considering the spectral and return periods that are of typical interestfor earthquake engineering. Finally, a comparison with the SPSHA map based on a well-established source model for Italy is also provided.233 107 - PublicationRestrictedOperational (short-term) earthquake loss forecasting in Italy(2015)
; ; ; ; ; ; ; ;Iervolino, I.; Università di Napoli Federico II ;Chioccarelli, E.; Università di Napoli Federico II ;Giorgio, M.; Seconda Università degli Studi di Napoli ;Marzocchi, W.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Zuccaro, G.; Università di Napoli Federico II ;Dolce, M.; Dipartimento della Protezione Civile ;Manfredi, G.; Università di Napoli Federico II; ;; ; ; ; The seismological community is currently developing operational earthquake forecasting (OEF) systems that aim to estimate, based on continuous ground motion recording by seismic networks, the rates of events exceeding a certain magnitude threshold in an area of interest and in a short-period of time (days to weeks); i.e., the seismicity. OEF may be possibly used for short-term seismic risk management in regions affected by seismic swarms only if its results may be the input to compute, in a probabilistically sound manner, consequence-based risk metrics. The present paper reports the investigation about feasibility of short-term risk assessment, or operational earthquake loss forecasting (OELF), in Italy. The approach is that of performance-based earthquake engineering, where the loss rates are computed by means of hazard, vulnerability, and exposure. The risk is expressed in terms of individual and regional measures, which are based on short-term macroseismic intensity, or ground motion intensity, hazard. The vulnerability of the built environment relies on damage probability matrices empirically calibrated for Italian structural classes, and exposure data in terms of buildings per vulnerability class and occupants per building typology. All vulnerability and exposure data are at the municipality scale. The procedure set-up, which is virtually independent on the seismological model used, is implemented in an experimental OELF system, which continuously process OEF information to produce weekly nationwide risk maps. This is illustrated by a retrospective application to the 2012 Pollino (southern Italy) seismic sequence, which provides insights on the capabilities of the system and on the impact, on short-term risk assessment, of the methodology currently used for OEF in Italy.451 34