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  • Articles  (13)
  • 04. Solid Earth::04.06. Seismology::04.06.02. Earthquake interactions and probability  (8)
  • 04. Solid Earth::04.06. Seismology::04.06.11. Seismic risk  (5)
  • EPSL
  • 1
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    Impact on loss/risk assessments of inter-model variability in vulnerability analysis (2013)
    Springer Science+Business Media B.V.
    Details
    Publication Date: 2020-11-18
    Description: Fragility curves (FCs) constitute an emerging tool for the seismic risk assessment of all elements at risk. They express the probability of a structure being damaged beyond a specific damage state for a given seismic input motion parameter, incorporating the most important sources of uncertainties, that is, seismic demand, capacity and definition of damage states. Nevertheless, the implementation of FCs in loss/risk assessments introduces other important sources of uncertainty, related to the usually limited knowledge about the elements at risk (e.g., inventory, typology). In this paper, within a Bayesian framework, it is developed a general methodology to combine into a single model (Bayesian combined model, BCM) the information provided by multiple FC models, weighting them according to their credibility/ applicability, and independent past data. This combination enables to efficiently capture inter-model variability (IMV) and to propagate it into risk/loss assessments, allowing the treatment of a large spectrum of vulnerability-related uncertainties, usually neglected. As case study, FCs for shallow tunnels in alluvial deposits, when subjected to transversal seismic loading, are developed with two conventional procedures, based on a quasi-static numerical approach. Noteworthy, loss/risk assessments resulting from such conventional methods show significant unexpected differences. Conventional fragilities are then combined in a Bayesian framework, in which also probability values are treated as random variables, characterized by their probability density functions. The results show that BCM efficiently projects the whole variability of input models into risk/loss estimations. This demonstrates that BCM is a suitable framework to treat IMV in vulnerability assessments, in a straightforward and explicit manner.
    Description: Published
    Description: 723-746
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: open
    Keywords: Fragility curves ; Bayesian approach ; Epistemic uncertainty ; Inter-model variability ; Seismic risk ; 04. Solid Earth::04.06. Seismology::04.06.11. Seismic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
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    Systemic seismic risk assessment of road networks in urban areas (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2021-03-18
    Description: This article presents an integrated approach for the probabilistic systemic risk analysis of a road network considering spatial seismic hazard with correlation of ground motion intensities, vulnerability of the network components, and the effect of interactions within the network, as well as, between roadway components and built environment to the network functionality. The system performance is evaluated at the system level through a global connectivity performance indicator, which depends on both physical damages to its components and induced functionality losses due to interactions with other systems. An object-oriented modeling paradigm is used, where the complex problem of several interacting systems is decomposed in a number of interacting objects, accounting for intra- and interdependencies between and within systems. Each system is specified with its components, solving algorithms, performance indicators and interactions with other systems. The proposed approach is implemented for the analysis of the road network in the city of Thessaloniki (Greece) to demonstrate its applicability. In particular, the risk for the road network in the area is calculated, specifically focusing on the short-term impact of seismic events (just after the earthquake). The potential of road blockages due to collapses of adjacent buildings and overpass bridges is analyzed, trying to individuate possible criticalities related to specific components/subsystems. The application can be extended based on the proposed approach, to account for other interactions such as failure of pipelines beneath the road segments, collapse of adjacent electric poles, or malfunction of lighting and signaling systems due to damage in the electric power network.
    Description: Published
    Description: 524–540
    Description: 3T. Pericolosità sismica e contributo alla definizione del rischio
    Description: JCR Journal
    Description: restricted
    Keywords: Systemic vulnerability ; 04. Solid Earth::04.06. Seismology::04.06.11. Seismic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
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    Accounting for Epistemic Uncertainty in PSHA: Logic Tree and Ensemble Modeling (2015)
    Seismological Society of America
    Details
    Publication Date: 2021-05-12
    Description: Any trustworthy probabilistic seismic hazard analysis (PSHA) has to account for the intrinsic variability of the system (aleatory variability) and the limited knowledge of the system itself (epistemic uncertainty). The most popular framework for this purpose is the logic tree. Notwithstanding its vast popularity, the logic tree outcomes are still interpreted in two different and irreconcilable ways. In one case, practitioners claim that the mean hazard of the logic tree is the hazard and the distribution of all outcomes does not have any probabilistic meaning. On the other hand, other practitioners describe the seismic hazard using the distribution of all logic tree outcomes. In this paper, we explore in detail the reasons of this controversy about the interpretation of logic tree, showing that the distribution of all outcomes is more appropriate to provide a joined full description of aleatory variability and epistemic uncertainty. Then, we provide a more general framework - that we name ensemble modeling - in which the logic tree outcomes can be embedded. In this framework, the logic tree is not a classical probability tree, but it is just a technical tool that samples epistemic uncertainty. Ensemble modeling consists of inferring the parent distribution of the epistemic uncertainty from which this sample is drawn. Ensemble modeling offers some remarkable additional features. First, it allows a rigorous and meaningful validation of any PSHA; this is essential if we want to keep PSHA into a scientific domain. Second, it provides a proper and clear description of the aleatory variability and epistemic uncertainty that can help stakeholders to appreciate the whole range of uncertainties in PSHA. Third, it may help to reduce the computational time when the logic tree becomes computationally intractable because of the too many branches.
    Description: Published
    Description: 2151-2159
    Description: 1SR. TERREMOTI - Servizi e ricerca per la Società
    Description: JCR Journal
    Description: reserved
    Keywords: seismic hazard ; logic tree ; 04. Solid Earth::04.06. Seismology::04.06.11. Seismic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 4
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    Stochastical and Mathematical Modeling of Long-term Interaction among Earthquakes and between Earthquakes and Volcanic Eruptions (2010)
    Details
    Publication Date: 2017-04-04
    Description: At first, we investigate on the physical mechanisms responsible for for long-term interactions. It has been argued that postseismic relaxation field might be responsible of such long-term interactions; then, our first task is understand whether or not the postseismic stress field can produce not negligible perturbations (respect to the tectonic field) and lead to long-term variations on a seismogenetic system. The second task of this work is to systematically investigate on the effects of long-term interactions in the seismic data. In particular, we focus our attention on the perturbation induced by the greatest earthquakes of the last century, all occurred in the period 1952-1965. At global scale, we study the distribution of strong earthquakes (M ≥ 7.0), and specifically we try to understand whether spatial and temporal distribution of M ≥ 7.0 earthquakes occurred after 1965 is correlated with the perturbation due to the 5 giant earthquakes Kamchatka 1952, Aleutins 1957, Chile 1960, Alaska 1964, and Aleutins 1965. At local scale, we aim to understand the effects of long-term interactions on moderate seismicity. In particular, we study the effects of the two strongest event of the past century (Chile 1960 and Alaska 1964) in Southern California, where is available a catalog (complete with focal parameters estimation) for moderate seismicity (M ≥ 4.7) since 1933. Finally, we study the effects of long-term stress perturbations on volcanic systems. The interaction between strong tectonic earthquakes and volcanic eruptions has been found through various statistical analysis of catalogs [e.g., Linde and Sacks, 1998; Marzocchi, 2002; Marzocchi et al., 2002]. Anyway, some authors remain skeptical because of the retrospective approach used in those works. Therefore, here we aim to set an objective tool to accomplish a forward test to quantitatively analyze such a long-term interaction among earthquakes and volcanoes.
    Description: Dottorato di Ricerca in Geofisica, XVII Ciclo, Università di Bologna
    Description: Published
    Description: 3.1. Fisica dei terremoti
    Description: open
    Keywords: interaction ; postseismic ; 04. Solid Earth::04.06. Seismology::04.06.02. Earthquake interactions and probability
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: thesis
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  • 5
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    Variations of southern California seismicity: Empirical evidence and possible physical causes (2005)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: We investigate southern California seismicity in order to characterize its temporal evolution during the last decades. We analyze the time series composed of the number of events per year and the focal mechanisms of earthquakes since 1933. The results show a statistically significant nonstationarity, with a change that occurred in the 1960s in both time series. The seismicity before the change point is mostly characterized by a strike-slip focal mechanism of San Andreas type; after the 1960s the seismicity appears to show more scattered focal mechanisms and a lower seismicity rate. We provide a possible physical explanation of the significant nonstationarity by modeling the postseismic stress perturbation field induced by the two strongest earthquakes of the last century, the Chile (1960) and Alaska (1964) earthquakes, which both occurred in the 1960s. To first order, the postseismic stress rate seems to be in agreement with the observed changes in seismicity, supporting a causality hypothesis. The model also foretells the future behavior of the trend of southern California seismicity; this forward prediction provides an important opportunity to validate the causal hypothesis of a remote (and long-term) coupling between earthquakes.
    Description: Published
    Description: reserved
    Keywords: lon-term interaction ; post-seismic field ; nonstationarities ; southern california ; 04. Solid Earth::04.06. Seismology::04.06.02. Earthquake interactions and probability
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Format: 339642 bytes
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  • 6
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    On the Occurrence of Large Earthquakes: New Insights From a Model based on Interacting Faults Embedded in a Realistic Tectonic Setting (2008)
    Details
    Publication Date: 2012-02-03
    Description: Earthquake occurrence stems from a complex interaction of processes that are still partially unknown. This lack of knowledge is revealed by the different statistical distributions that have been so far proposed, and by the different beliefs about the role of some key components as the tectonic setting, fault recurrence, seismic clusters, and fault interaction. Here, we explore these issues through a numerical model based on a realistic interacting fault system. We use an active fault system in Central Italy responsible for moderate to large earthquakes, where geometric and kinematic parameters of each structure can be confidently assessed. Then, we generate synthetic catalogs by modeling different seismogenic processes and allowing co- and post-seismic fault interaction. The comparison of synthetic and real seismic catalogs highlights many interesting features: (i) synthetic seismic catalogs reproduce the short-term clustering and the long-term modulation observed in the historical catalog of the last centuries; (ii) a recurrent model of earthquake occurrence on faults is more effective than a Poisson model to explain such short-term and long-term time features; (iii) a realistic fault pattern is a key component to generate stochasticity in the seismic catalog, preventing a systematic time ”synchronization” of strongly coupled faults; (iv) such a stochasticity may put strong limits to the forecasting capability of models based on fault interaction, even though the latter is a key component of the process. Finally, the model allows explicit predictions on future paleoseismological observations to be made.
    Description: In press
    Description: 3.1. Fisica dei terremoti
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: open
    Keywords: Earthquake interactions ; probability ; 04. Solid Earth::04.06. Seismology::04.06.02. Earthquake interactions and probability
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 7
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    Forecasting the effects of the Andaman Islands - Sumatra megathrust earthquakes (Dec. 2004 and Mar. 2005) on volcanoes in the surrounding area (2006)
    Details
    Publication Date: 2017-04-04
    Description: The Andaman Islands - Sumatra earthquake (Mw = 9.3, Dec. 2004) and the subsequent Sumatra earthquake (Mw = 8.7, Mar. 2005) represent one of most energetic sequence of earthquakes ever recorded. Since both events occurred in a strongly active volcanic region, their exceptionally strong stress perturbation gives the opportunity to understand the effects of stress perturbations on volcanic systems. Here, we set the rules for a forward test of the causal relationship between stress perturbation and subsequent volcanic eruptions, by means of the comparison of the spatio-temporal distribution of the eruptions which follow the earthquakes with the co- and the post-seismic stress field due to the earthquakes. In practice, we forecast that the volcanic activity of the next 30 years will be significantly promoted by the stress perturbation; thus, we define the rules for an objective test of such an hypothesis. Given the extremely high values of stress perturbation due to this sequence of earthquakes, the results of our test will definitively provide a reliable evaluation of the possible statistical impact of earthquake-eruption interaction on long-term volcanic hazard assessments.
    Description: Unpublished
    Description: open
    Keywords: Earthquake-volcano interaction, stastical model, stress field, ; stress field ; Statistical model ; 04. Solid Earth::04.06. Seismology::04.06.02. Earthquake interactions and probability ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 05. General::05.01. Computational geophysics::05.01.04. Statistical analysis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: manuscript
    Format: 724315 bytes
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  • 8
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    On the Occurrence of Large Earthquakes: New Insights from a Model based on Interacting Faults Embedded in a Realistic Tectonic Setting (2009)
    Details
    Publication Date: 2017-04-04
    Description: Earthquake occurrence stems from a complex interaction of processes that are still partially unknown. This lack of knowledge is revealed by the different statistical distributions that have been so far proposed and by the different beliefs about the role of some key components as the tectonic setting, fault recurrence, seismic clusters, and fault interaction. Here, we explore these issues through a numerical model based on a realistic interacting fault system. We use an active fault system in central Italy responsible for moderate to large earthquakes, where geometric and kinematic parameters of each structure can be confidently assessed. Then, we generate synthetic catalogs by modeling different seismogenic processes and allowing coseismic and postseismic fault interaction. The comparison of synthetic and real seismic catalogs highlights many interesting features: (1) synthetic seismic catalogs reproduce the short-term clustering and the long-term modulation observed in the historical catalog of the last centuries; (2) a recurrent model of earthquake occurrence on faults is more effective than a Poisson model to explain such short-term and long-term time features; (3) a realistic fault pattern is a key component to generate stochasticity in the seismic catalog, preventing a systematic time ‘‘synchronization’’ of strongly coupled faults; (4) such a stochasticity may put strong limits to the forecasting capability of models based on fault interaction, even though the latter is a key component of the process. Finally, the model allows explicit predictions on future paleoseismological observations to be made.
    Description: Published
    Description: B01307
    Description: 3.1. Fisica dei terremoti
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: reserved
    Keywords: Earthquake interactions ; Probability ; Central Italy ; Fault ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous ; 04. Solid Earth::04.06. Seismology::04.06.02. Earthquake interactions and probability
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 9
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    Long-term influence of giant earthquakes: backward empirical evidence and forward test (2008)
    Seismological Society of America
    Details
    Publication Date: 2017-04-04
    Description: We investigate the capability of the strongest earthquakes to modify sig- nificantly the seismicity in a wide spatiotemporal window. In particular, we show that the strongest earthquakes of last century were probably able to influence the seismicity at large spatiotemporal distances, extending their reach over thousands of kilometers and decades later. We report statistically significant differences in worldwide seismi- city before and after the occurrence of the strongest earthquakes of the last century, whose perturbation is modeled by means of coseismic and postseismic stress varia- tions. This long-term coupling has produced time variations in worldwide seismic activity that appear related to the physical coupling between the focal mechanism of source earthquakes and the tectonic setting of each zone. These results could provide new important insights on seismic hazard assessment because they raise doubts on the validity of two paradigms; that is, the steadiness of the mainshock rate and the iso- lation of a seismic region from the surrounding areas. Finally, in addition to this back- ward analysis, we also provide a formal forward test by forecasting the effects on global seismicity of the recent Sumatra–Andaman earthquakes; this is maybe a unique chance to test the long-term hypothesis with an independent dataset that avoids, by definition, any kind of (often unconscious) optimization of the results that is an un- avoidable possibility in backward analyses.
    Description: Published
    Description: 1102–1112
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: open
    Keywords: Long-term earthquake interaction ; Forward Test ; 04. Solid Earth::04.06. Seismology::04.06.02. Earthquake interactions and probability
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 10
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    Probabilistic hazard for seismically induced tsunamis: accuracy and feasibility of inundation maps (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: Probabilistic tsunami hazard analysis (PTHA) relies on computationally demanding numerical simulations of tsunami generation, propagation, and non-linear inundation on high-resolution topo-bathymetric models. Here we focus on tsunamis generated by co-seismic sea floor dis- placement, that is, on Seismic PTHA (SPTHA). A very large number of tsunami simulations are typically needed to incorporate in SPTHA the full expected variability of seismic sources (the aleatory uncertainty). We propose an approach for reducing their number. To this end, we (i) introduce a simplified event tree to achieve an effective and consistent exploration of the seismic source parameter space; (ii) use the computationally inexpensive linear approximation for tsunami propagation to construct a preliminary SPTHA that calculates the probability of maximum offshore tsunami wave height (H Max) at a given target site; (iii) apply a two-stage filtering procedure to these ‘linear’ SPTHA results, for selecting a reduced set of sources and (iv) calculate ‘non-linear’ probabilistic inundation maps at the target site, using only the selected sources. We find that the selection of the important sources needed for approximating probabilistic inundation maps can be obtained based on the offshore HMax values only. The filtering procedure is semi-automatic and can be easily repeated for any target sites. We describe and test the performances of our approach with a case study in the Mediterranean that considers potential subduction earthquakes on a section of the Hellenic Arc, three target sites on the coast of eastern Sicily and one site on the coast of southern Crete. The comparison between the filtered SPTHA results and those obtained for the full set of sources indicates that our approach allows for a 75–80 per cent reduction of the number of the numerical simulations needed, while preserving the accuracy of probabilistic inundation maps to a reasonable degree.
    Description: Published
    Description: 574-588
    Description: 3T. Pericolosità sismica e contributo alla definizione del rischio
    Description: JCR Journal
    Description: restricted
    Keywords: Tsunami ; Hazard ; Probabilistic ; Subduction ; Mediterranean ; SPTHA ; 04. Solid Earth::04.06. Seismology::04.06.02. Earthquake interactions and probability ; 04. Solid Earth::04.07. Tectonophysics::04.07.04. Plate boundaries, motion, and tectonics ; 04. Solid Earth::04.07. Tectonophysics::04.07.06. Subduction related processes
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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