ALBERT

Description: N/A

Description: Published

Description: 75-83

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: 4.2. TTC - Modelli per la stima della pericolosità sismica a scala nazionale

Description: N/A or not JCR

Description: reserved

Description: This study investigates the engineering applicability of two conceptually different finite-fault simulation techniques. We focus our attention on two important aspects: first to quantify the capability of the methods to reproduce the observed ground-motion parameters (peaks and integral quantities); second to quantify the dependence of the strong-motion parameters on the variability in the large-scale kinematic definition of the source (i.e. position of nucleation point, value of the rupture velocity and distribution of the final slip on the fault). We applied an approximated simulation technique, the Deterministic-Stochastic Method DSM, and a broadband technique, the Hybrid-Integral-Composite method HIC, to model the 1984 Mw 5.7 Gubbio, central Italy, earthquake, at 5 accelerometric stations. We first optimize the position of nucleation point and the value of rupture velocity for three different final slip distributions on the fault by minimizing an error function in terms of acceleration response spectra in the frequency band from 1 to 9 Hz. We found that the best model is given by a rupture propagating at about 2.65 km/s from a hypocenter located approximately at the center of the fault. In the second part of the paper we calculate more than 2400 scenarios varying the kinematic source parameters. At the five sites we compute the residuals distributions for the various strong-motion parameters and show that their standard deviations depend on the source-parameterization adopted by the two techniques. Furthermore, we show that, Arias Intensity and significant duration are characterized by the largest and smallest standard deviation, respectively. Housner Intensity results better modeled and less affected by uncertainties in the source kinematic parameters than Arias Intensity. The fact that the uncertainties in the kinematic model affects the variability of different ground-motion parameters in different ways has to be taken into account when performing hazard assessment and earthquake engineering studies for future events.

Description: In press

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: JCR Journal

Description: open

Description: In the months following the April 6th, 2009, L’Aquila earthquake, several Italian and foreign research institutions installed dozens of seismic stations to monitor more than 100 localities with the aim of studying the local site effects in the epicentral area (upper and middle Aterno valley). The stations (accelerometers and velocimeters) have been deployed inside or very close to the inhabited areas. Among the investigated sites there are Onna, where almost the totality of the buildings collapsed, and the historic centre of L’Aquila, both towns suffering many casualties. The preliminary results for the examined sites show an extreme variability of ground motion and significant amplification for the most damaged localities.

Description: In press

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: N/A or not JCR

Description: open

Description: Il terremoto del 6 aprile 2009 è sicuramente uno degli eventi per il quale si è avuto il maggior numero di registrazioni; questo ha fatto sì che sono diventate possibili molte analisi, anche molto particolareggiate, e tra queste il confronto tra gli spettri di risposta registrati e quelli previsti dalle recenti Norme Tecniche per le Costruzioni (rilasciate nel 2008 e in vigore in via definitiva dal 1° luglio 2009, NTC08). Questo tipo di confronto è stato sicuramente suggerito dal fatto che in alcune stazioni in area epicentrale si siano superati i valori di PGA previsti dalla mappa di riferimento della pericolosità sismica (MPS04, Gruppo di Lavoro MPS, 2004) per il periodo di ritorno di 475 anni. Viene quindi affrontato dapprima il problema se le registrazioni di un unico terremoto possono essere utilizzate per validare il modello di riferimento e se le eventuali differenze possano pertanto considerarsi significative. Viene poi analizzato il ruolo di alcuni elementi di input della valutazione della pericolosità sismica, in particolar modo le relazioni di attenuazione utilizzate, generalmente considerate poco affidabili per brevi distanze dalla faglia. Viene infine valutata la procedura adottata nella predisposizione di NTC08, che sembra aver privilegiato un migliore adattamento agli spettri a pericolosità uniforme rilasciati da INGV (http://esse1.mi.ingv.it) rispetto a considerazioni di cautela contenute sia negli stessi dati di pericolosità sismica che nella prassi corrente in molti paesi. La serie di confronti tra registrazioni accelerometriche e spettri di progetto previsti dalle NTC08 che è stata condotta suggerisce diverse chiavi di lettura che verranno presentate e discusse.

Description: Published

Description: Trieste

Description: 4.2. TTC - Modelli per la stima della pericolosità sismica a scala nazionale

Description: open

Description: In the recent years, two Italian research projects have been devoted to the simulation of ground shaking scenarios in different areas. A large part of the activities has been performed in the Umbria region and was in particular related to the 1997 Colfiorito earthquake. In general the statistical-deterministic approach was adopted for evaluating the scenarios for strong motion parameters (peak values, spectral ordinates, signal integral quantities, and so on) associated with the occurrence of a characteristic earthquake on a given fault. This approach is based on the realistic occurrence of a single earthquake related to the fracture of an a priori well identified active fault. According to the characteristic earthquake model, an earthquake rupture can repeatedly occurs along the same fault (or fault system) with an almost constant geometry, mechanism and seismic moment, these parameters being mainly related to the direction and intensity of the large scale tectonic stress regime. These ideas are supported by numerous paleoseismic studies of active faults in different tectonic environments [e.g., Pantosti and Valensise, 1990]. On the other hand, each faulting process may not repeat the same style of nucleation, propagation and arrest during successive rupture episodes occurring along a given fault zone, depending these characteristics on the pre-fracturing conditions of rock strength and/or yielding stress along the fault zone. It is therefore assumed that the large scale source characteristics (i.e., fault size and position, focal mechanism and seismic moment) are a priori known as the result of previous geological, geophysical and historical seismicity investigations. The variability of the rupture process is expected to produce variable strong ground motions at the earth surface, depending on the distribution of the kinematic parameters (final slip distribution, rupture velocity, slip duration …) along the faulting surface. In order to account for the possible variation of the source process from one rupture event to another, a large number of synthetic seismograms should be computed for different (and possible) rupture histories occurring along the characteristic fault selected, so to provide a representative set of strong motion records to be used for hazard estimation. By this strategy, the massive computation of synthetics for different possible rupture models does not provide a single earthquake scenario (as for the standard deterministic approach) but a set of possible scenarios whose variability substantially reflects the heterogeneity of the source process. The advantage of this approach is that the variability of the selected strong ground motion parameter at a given site can be described by the statistical quantities inferred from the large number of simulations available. The earthquake scenario can then be represented, for example, by a couple of maps, one describing the spatial distribution of the mean value of the considered ground motion parameter and the other representing the associated variability for example in terms of standard deviation.

Description: Published

Description: Roma, Università degli Studi Roma TRE

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: open

Description: This study investigates the engineering applicability of two conceptually different finite-fault simulation techniques. We focus our attention on two important aspects: first to quantify the capability of the methods to reproduce the observed ground-motion parameters (peaks and integral quantities); second to quantify the dependence of the strong-motion parameters on the variability in the large-scale kinematic definition of the source (i.e., position of the nucleation point, value of the rupture velocity, and distribution of the final slip on the fault). We applied an approximated simulation technique, the deterministic-stochastic method and a broadband technique, the hybrid-integral-composite method, to model the 1984 Mw 5.7 Gubbio, central Italy, earthquake, at five accelerometric stations. We first optimize the position of the nucleation point and the value of the rupture velocity for three different final slip distributions on the fault by minimizing an error function in terms of acceleration response spectra in the frequency band from 1 to 9 Hz. We found that the best model is given by a rupture propagating at about 2:65 km=sec from a hypocenter located approximately at the center of the fault. In the second part of the article we calculate more than 2400 scenarios varying the kinematic source parameters. At the five sites we compute the residuals distributions for the various strongmotion parameters and show that their standard deviations depend on the source parameterization adopted by the two techniques. Furthermore, we show that Arias Intensity (AI) and significant duration are characterized by the largest and smallest standard deviation, respectively. Housner Intensity is better modeled and less affected by uncertainties in the source kinematic parameters than AI. The fact that the uncertainties in the kinematic model affects the variability of different ground-motion parameters in different ways has to be taken into account when performing hazard assessment and earthquake engineering studies for future events.

Description: Published

Description: 647-663

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: JCR Journal

Description: reserved

Description: The overall aim of Sub-Project 10 (Earthquake disaster scenario predictions and loss modelling for urban areas) has been to create a tool, based on state-of-the-art loss modelling software, to provide strong, quantified statements about the benefits of a range of possible mitigation actions, in order to support decision-making by urban authorities for seismic risk mitigation strategies. A further larger aim has been to contribute to a seismic risk mitigation policy for future implementation at European level. Among the European cities for which loss estimation studies have been carried out are Istanbul, Lisbon and Thessaloniki, and tools, using GIS mapping, have been developed by research teams in each of these cities; these were made available for further development to examine mitigation strategies within SP10. Related research studies – on ground motion estimation, on the assessment of human casualties, and on the evaluation of uncertainty have been carried out by other research teams across Europe which includes INGV, UCAM and USUR respectively. In all three of the cities, a common general approach to loss modelling has been adopted which includes representing the earthquake hazard as a set of alternative ground motion scenarios (typically those with an expected recurrence periods of 50 and 500 years), and applying the ground motion over a target area of known population and building stock. Losses have then been estimated for this target area in terms of levels of building damage and human casualties expected both in the existing state of the target area, and after certain selected potential mitigation actions have been carried out. This has been done in each case using building stock classifications and vulnerability data specific to the particular city concerned. In each case the scope of the proposed mitigation action has been described, and its expected benefit in terms of reduced losses and human casualties has been determined with some preliminary assessment of uncertainty.

Description: LessLoss - Risk Mitigation for Earthquakes and Landslides, SP10 "Earthquake Scenarios, Loss Modelling and Mitigation for Urban Areas" (coord. R.Spence). EC Project -Sixth Framework Programme. Priority 1.1.6.3 - Global Change and Ecosystems, Project No.:GOCE-CT-2003-505488

Description: Published

Description: 4.2. TTC - Scenari e mappe di pericolosità sismica

Description: open

Description: The main goal of this report is the computation of the bedrock seismic motion at 5 municipalities located in the Molise area (Bonefro, S.Giuliano, Colletorto, S.Croce di Magliano, Ripabottoni, hereafter referred to as sites BNF, SGI, CLT, SCM and RPB, respectively). This area represents one of the validation case studies, planned in the framework of Project S3 which aim is the production of ground shaking scenarios for moderate magnitude earthquakes. Indeed, the recently occurred Molise earthquake represents a proper opportunity to compare synthetic simulations with real data. Acceleration time series were recorded during the October 31, 2002 and November 1, 2002 main shocks by analog and digital instruments managed by the Italian Civil Protection Department [DPC-SSN, 2004] while acceleration and velocity records were collected during the first month of seismic activity by DPC, INGV, INOGS, Dip.Te.Ris.(Genoa) (see §2.1 and Deliverable D6). Both strong and weak motion data were employed to infer regional ground motion prediction equations and spectral attenuation models (§2.3 and §2.4) while acceleration time series recorded during the first main shock by nearby stations were used to constrain the seismogenic sources of the October 31 and November 1, 2002 twin earthquakes (§4.1). Bedrock shaking scenarios at different level of complexity were produced by ground motion prediction equations (scenarios of level 0, §4.2), high frequency (f〉1Hz) simulations (scenarios of level I, §4.3) and broad band (0-12 Hz) simulations (scenarios of level II, §4.4). Comparison of results obtained with different simulations methods confirms the complexity of the Molise area as regard to both seismogenic and attenuation properties of the crust. Especially for this area the ground motion prediction is constrained by the demand of simulations reproducing different features of the seismic wavefield. In particular, the input motion for site effect modelling, performed at sites located in the epicentral area, was computed with a broad band technique able to reproduce the complete wave field in the frequency band 0-10 Hz in terms of acceleration time series (scenarios of level II scenarios).

Description: Progetto INGV-DPC S3 “Scenari di scuotimento in aree di interesse prioritario e/o strategico”

Description: Published

Description: 4.2. TTC - Scenari e mappe di pericolosità sismica

Description: open

Description: L’INGV (http://www.mi.ingv.it/) svolge in Lombardia ricerche nel campo della mitigazione del rischio sismico, mediante studi mirati al miglioramento delle conoscenze sulla storia sismica, sul modello strutturale legato al regime tettonico in atto e alla definizione del moto del suolo atteso. Accanto alle indagini necessarie alla caratterizzazione sismogenetica e dei possibili effetti dello scuotimento sismico, si pone l’attività di monitoraggio sismico, che la Sezione di Milano-Pavia espleta mediante la rete accelerometrica (RAIS, http://rais.mi.ingv.it/) che consta di 20 postazioni distribuite in prevalenza sul territorio regionale. In un recente lavoro di sintesi - di studi pluriennali su fonti storiche e di revisioni critiche di materiali pubblicati - si è tentato di colmare l’evidente carenza conoscitiva sulle caratteristiche della sismicità storica dell’area lombarda. Tale carenza è particolarmente evidente se si rapportano le informazioni oggi disponibili sui terremoti del passato in quest’area con quelle relative al settore veneto-friulano. La regione analizzata, compresa tra il bacino del fiume Adda e il Lago di Garda, è stata caratterizzata da alcuni terremoti con Mw〉5.5 (es., 1117, Veronese; 1222, Brescia; 1901, Salò) e vari eventi con Mw compresa fra 4.8 e 5.5 (es., 1065, Brescia; 1396, Monza; 1642, Bergamo). Per molti degli eventi sismici fino al 1700 le informazioni sono desumibili soltanto da scarse fonti storiche. La determinazione epicentrale e l’attribuzione della magnitudo per tali eventi sono da considerarsi, pertanto, con una certa cautela al fine di definire le caratteristiche sismiche del territorio. I terremoti del 1117 e del 1222, in tale contesto, rappresentano un’eccezione rispetto ai dati generalmente disponibili. E tuttavia vari problemi tuttora aperti rendono assai difficile l’utilizzo della distribuzione del danno attribuibile a questi eventi nella prospettiva di un’affidabile parametrizzazione. Le indagini geologico-strutturali e di geologia del Quaternario, finalizzate a definire un quadro strutturale compatibile con il regime tettonico in atto, sono necessarie per giustificare la storia sismica e, in sostanza, per definire il comportamento sismogenetico della regione. Le geometrie dei sistemi di faglia attivi alpini sono ora sufficientemente noti. Le conoscenze permettono di formulare ipotesi sismotettoniche relative all’origine dei terremoti dell’area gardesana e del Bresciano. In via di definizione sono invece le geometrie dei fronti appenninici, cui sono attribuibili i terremoti al di sopra della soglia nel settore padano. Le ricerche attuali sono altresì indirizzate ad una migliore caratterizzazione del complesso settore compreso tra la parte meridionale del Lago di Garda (area di Sirmione), Verona e Mantova, all’interno del quale potrebbe collocarsi l’area epicentrale del terremoto del 1117 (o una delle aree epicentrali, qualora si considerasse questo evento come rappresentato da una sequenza sismica). Uno dei settori regionali con maggiore frequenza di eventi sismici è l’area gardesana occidentale, per questo motivo la rete di monitoraggio presenta una notevole densità di postazioni nel Bresciano e se ne è pianificato l’addensamento nel Veronese. Nel corso del 2007, la rete ha consentito la registrazione di 516 forme d’onda relative a 28 eventi locali e regionali (di cui una decina localizzati nell’area citata) con magnitudo da 1.3 a 4.2, di cui sono stati calcolati i parametri di interesse ingegneristico. L’analisi delle registrazioni ha permesso di ricavare informazioni utili per il calcolo di scenari di scuotimento. Un esempio di taali applicazioni è rappresentato dallo scenario realizzato utilizzando come terremoto di riferimento l'evento del 24 Novembre 2004 (M 5.2).

Description: Published

Description: Milano

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: open

Description: In this paper, we adopt three ground-motion simulation techniques (EXSIM, Motazedian and Atkinson, 2005, DSM, Pacor et al., 2005 and HIC, Gallovič and Brokešová, 2007), with the aim of investigating the different performances in near-fault strong-motion modeling and prediction from past and future events. The test case is the 1980, M 6.9, Irpinia earthquake, the strongest event recorded in Italy. First, we simulate the recorded strong-motion data and validate the model parameters by computing spectral acceleration and peak amplitudes residual distributions. The validated model is then used to investigate the influence of site effects and to compute synthetic ground motions around the fault. Afterward, we simulate the expected ground motions from scenario events on the Irpinia fault, varying the hypocenters, the rupture velocities and the slip distributions. We compare the median ground motions and related standard deviations from all scenario events with empirical ground motion prediction equations (GMPEs). The synthetic median values are included in the median ± one standard deviation of the considered GMPEs. Synthetic peak ground accelerations show median values smaller and with a faster decay with distance than the empirical ones. The synthetics total standard deviation is of the same order or smaller than the empirical one and it shows considerable differences from one simulation technique to another. We decomposed the total standard deviation into its between-scenario and within-scenario components. The larger contribution to the total sigma comes from the latter while the former is found to be smaller and in good agreement with empirical inter-event variability.

Description: In press

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: JCR Journal

Description: restricted