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  • 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion  (59)
  • Seismological Society of America  (30)
  • Springer  (29)
  • Blackwell Publishing Ltd
  • Essen : Verl. Glückauf
  • Krefeld : Geologischer Dienst Nordhein-Westfalen
  • 2010-2014  (27)
  • 2005-2009  (32)
  • 1965-1969
  • 1960-1964
Collection
Years
  • 2010-2014  (27)
  • 2005-2009  (32)
  • 1965-1969
  • 1960-1964
  • 2015-2019  (5)
Year
  • 1
    Publication Date: 2019-12-13
    Description: The city of L’Aquila is built on a deep intramontane basin filled by silty clay of lacustrine origin with average S-wave velocity of about 725 m=s, topped by a calcareous breccias unit with a higher speed of about 900 m=s. New geologic and geophysical investigations following the 6 April 2009 Mw 6.3 L’Aquila, Italy, earthquake have allowed us to develop a new velocity model for the basin deposits that, coupled with the inversion of velocity, includes lateral velocity variations in the top breccia layer and a newly found red silts unit, the Limi Rossi del Colle dell’Aquila (LRCA). The city area where the LRCA unit outcrops is correlated with clusters of reinforced concrete buildings that collapsed in the nor- mal faulting earthquake. We simulate the 2D seismic response of this new velocity model along two orthogonal cross sections and compare the synthetic spectral ratios to the experimental ones evaluated using aftershock recordings. As a result, taking into account the full scatter about the mean of the observed spectral ratios, we are able to predict not only the main features of the primary observed low-frequency resonance peak, but also the level of amplification at high frequency at most of the sites investigated.
    Description: Published
    Description: 1374–1388
    Description: 3T. Pericolosità sismica e contributo alla definizione del rischio
    Description: JCR Journal
    Description: restricted
    Keywords: L'Aquila, spectral ratios, observation and modeling, high frequency, ground motion amplification ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
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    Seismological Society of America
    Publication Date: 2017-04-04
    Description: Intensity scales define the criteria used to determine different levels of shaking in relation to environmental effects. Objective evaluations of low intensity degrees based on transient effects may be difficult. In particular, estimations for the number of people feeling an earthquake are critical, and are qualitatively described by words such as “few”, “many”, and “most” for determining various intensity levels. In general, such qualitative amounts are converted into specific percentages for each macroseismic scale. Additionally, estimations of macroseismic intensity are influenced by variables that are mentioned in macroseismic scale degree descriptions. For example, the Mercalli-Cancani-Sieberg (MCS; Sieberg, 1930) and the Modified Mercalli Intensity (MMI) scales (Wood and Neumann, 1931) describe the intensity II as “Felt only by a few people, extremely susceptible, in perfectly quiet situations, almost always on the upper floors of buildings”. Another example is the European Macroseismic Scale (EMS) (Grunthal, 1998) that describes the intensity V as “felt indoors by most, outdoors by few. Many sleeping people awake”. In this work, we focus on two variables referred to as people’s physical “situation” (what were you doing?), here categorized as “sleeping”, “at rest”, or “in motion”; and the observer’s “location”, here categorized as “higher floors”, “lower floors”, and “outdoors”. Both variables have a partial influence on intensity assessments because they condition vibration perception. However, it is important to study, using an experimental method, the weights of these variables in the quantification of felt effects. Musson (2005a) also recognized the influence of such conditions on the number of people feeling an earthquake, stating that the proportion of people in different conditions “are generally difficult to quantify in any case”. Today, we have a large amount of data available through the macroseismic web site “haisentitoilterremoto” associated with specific observer conditions. Using this data, a study of these effects is possible. For this analysis, we placed attention on transitory effects that, in the past, could not be easily studied due to the intrinsic difficulty in collecting this type of data. The aim of this work was to specifically analyze and quantify how the observer’s “situation” and “location” influence earthquake perception suggesting a new scale description that can be easily used for low intensity estimation.
    Description: Published
    Description: 306-313
    Description: 3T. Pericolosità sismica e contributo alla definizione del rischio
    Description: 4IT. Banche dati
    Description: JCR Journal
    Description: open
    Keywords: macroseismic scale ; earthquake perception ; macroseismic questionnaire ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 3
    Publication Date: 2017-04-04
    Description: A temporary seismic network composed of 11 stations was installed in the city of Potenza (Southern Italy) to record local and regional seismicity within the context of a national project funded by the Italian Department of Civil Protection (DPC). Some stations were moved after a certain time in order to increase the number of measurement points, leading to a total of 14 sites within the city by the end of the experiment. Recordings from 26 local earthquakes (Ml 2.2−3.8 ) were analyzed to compute the site responses at the 14 sites by applying both reference and non-reference site techniques. Furthermore, the Spectral Intensity (SI) for each local earthquake, as well as their ratios with respect to the values obtained at a reference site, were also calculated. In addition, a field survey of 233 single station noise measurements within the city was carried out to increase the information available at localities different from the 14 monitoring sites. By using the results of the correlation analysis between the horizontal-to-vertical spectral ratios computed from noise recordings (NHV) at the 14 selected sites and those derived by the single station noise measurements within the town as a proxy, the spectral intensity correction factors for site amplification obtained from earthquake analysis were extended to the entire city area. This procedure allowed us to provide a microzonation map of the urban area that can be directly used when calculating risk scenarios for civil defence purposes. The amplification factors estimated following this approach show values increasing along the main valley toward east where the detrital and alluvial complexes reach their maximum thickness.
    Description: Published
    Description: 493-516
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: restricted
    Keywords: site effect ; seismic noise ; spectral intensity ; correlation ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 4
    Publication Date: 2017-04-04
    Description: On 20 May 2012, at 02:03:52 GMT, an earthquake with Mw 6.1 (RCMT, http://www.bo.ingv.it/RCMT) occurred in northern Italy striking a densely populated area. The mainshock was followed a few hours later by two severe aftershocks having the same local magnitude (Ml 5.1, 1 and 2 in Figure 1a), and by hundreds of smaller aftershocks. Nine days later, on 29 May, at 07:00:03 GMT, a second event with moment magnitude Mw 6.0 (RCMT, http://www.bo.ingv.it/RCMT) occurred to the west, on an adjacent fault segment. This event was also followed by hundreds of aftershocks, three of them having local magnitude 5.3, 5.2 and 5.1 (3, 4 and 5, respectively, in Figure 1a) (locations from Istituto Nazionale di Geofisica e Vulcanologia, hereinafter INGV, http://iside.rm.ingv.it/; Malagnini et al., 2012; Scognamiglio et al., 2012). Despite the moderate number of casualties if compared to other major events in the Italian history, the economic loss was extremely high, resulting in about EUR 5 billion (AON Benfield, 2012, http://www.aon.com/), as the majority of Italian industrial activities and infrastructures concentrate in this area, the eastern Po plain, which is the largest sedimentary basin in Italy. The mainshocks are associated to two thrust faults with an approximate E-W trend dipping to the South (Figure 1b). The majority of the faults in this region are located in the upper crust, at depths lower than 10 km. The two main shocks are among the strongest earthquakes generated by thrust faults ever recorded in Italy in the instrumental era. The Emilia sequence has been extensively recorded by several strong-motion networks, operating in the Italian territory and neighbouring countries. Some of the networks acquire continuous data streams at their national data centres, which are nodes of EIDA (European Integrated Data Archive, hhtp://eida.rm.ingv.it), a federation of several archives, so that the waveforms can be obtained immediately after the occurrence of an event. Other networks, such as the Italian accelerometric network (RAN), managed by the Italian Department of the Civil Protection (hereinafter DPC), distribute the acceleration waveforms through their web site (http://protezionecivile.gov.it). The data set explored in this study is relative to the six events of the sequence having Ml 〉 5 (Table 1) and consists in 365 accelerograms recorded within a distance of 200 km from the epicentres, that were provided by the permanent and temporary seismic networks of INGV, the Swiss Seismological Service (SED, http://www.seismo.ethz.ch/index) and the DPC.
    Description: Published
    Description: 629-644
    Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale
    Description: JCR Journal
    Description: open
    Keywords: Strong motion ; May-June 2012 Emilia Romagna earthquake sequence ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis ; 04. Solid Earth::04.06. Seismology::04.06.11. Seismic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 5
    Publication Date: 2017-04-04
    Description: The 6 April 2009 Mw 6.3 earthquake (Imax 9–10, Mercalli–Cancani– Sieberg [MCS]) struck the Abruzzi region of central Italy, producing severe damage in the city of L’Aquila. There was heavy damage in the city, especially in the central city area where unusual features of the damage pattern were immediately evident. The aim of this study is to correlate the distribution and the severity of the damage with the geological setting of the area, taking into account the characteristics of the building stock through time. Strong-motion recordings and ambient noise measurements taken soon after the mainshock and during the entire aftershock sequence showed variability in groundmotion amplification throughout the city. Factor of amplification (Fa) results are very high in the southern sector of the city, where the Limi Rossi del Colle dell’Aquila (LRCA) red silts outcrop, and quickly decrease northward, where LRCA is absent. This result correlates with the damage distribution to reinforced concrete (RC) buildings. In the southern sector the rate of collapse of RC buildings was 10%, versus 2% in the rest of the city. General conclusions highlight that the building stock of the city suffered different levels of damage that can be partially explained by the combination of building vulnerability and surface geology.
    Description: Published
    Description: 1543-1553
    Description: 4.2. TTC - Modelli per la stima della pericolosità sismica a scala nazionale
    Description: JCR Journal
    Description: restricted
    Keywords: l'aquila earthquake ; damage distribution ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion ; 04. Solid Earth::04.06. Seismology::04.06.05. Historical seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 6
    Publication Date: 2022-06-09
    Description: In the frame of the Italian research project INGV-DPC S2 (http://nuovoprogettoesse2.stru.polimi.it/), funded by the Dipartimento della Protezione Civile (DPC; National Civil Protection Department) within the agreement 2007-2009, a tool for probabilistic seismic hazard assessment (PSHA) was developed. The main goal of the project was to provide a flexible computational tool for PSHA; the requirements considered essential for the success of the project included: •ability to handle both stationary and non-stationary earthquake time-occurrence models; •ability to use ground-motion prediction models that are not parametric equations but probabilistic "footprints" of the intensities generated by earthquakes of known magnitude and focal characteristics. Usually, these footprints are results of ground motion simulations. Some commonly used programs (e.g., FRISK, by McGuire, 1978; SEISRISK III, by Bender and Perkins, 1987) and more recent and state-of-the-art tools (e.g. OpenSHA, by Field et al., 2003, http://www.opensha.org; OpenQuake, http://openquake.org) for PSHA were analyzed. It was decided to focus on CRISIS2007, which was already a mature and well known application (e.g., Kalyan Kumar and Dodagoudar, 2011; Teraphan et al., 2011; D’Amico et al., 2012; see also http://ecapra.org/CRISIS-2007), but also suitable for additional development and evolution since its source code is freely available on request. The computational tool resulted in an extensive redesign and renovation of the previous CRISIS2007 version. CRISIS is a computer program for PSHA, originally developed in the late 1980's using Fortran as programming language (Ordaz, 1991). In this format, still without a graphical user interface (GUI), it was distributed as part of SEISAN tools (Ottemöller et al., 2011). Ten years later, a GUI was constructed, generating what was called CRISIS99 (Ordaz, 1999). In this version, all the graphic features were written in Visual Basic, but the computation engine remained a Fortran dynamic link library. The reason for the use of mixed-language programming was that computations in Visual Basic were extremely slow. Around 2007 the program was upgraded, in view of the advantages offered by the object-oriented technologies. An object-oriented programming language was required and the natural choice was Visual Basic.Net. In the new version (called CRISIS2007), both the GUI and the computation engine were written in the same language. Finally, in the frame of the mentioned S2 project, starting from 2008, the program was split into two logical layers: core (CRISIS Core Library) and presentation (CRISIS2008). In addition, a new presentation layer was developed for accessing the same functionalities via Web (CRISISWeb). It is worth noting that CRISIS has been mainly written by people that are, at the same time, PSHA practitioners. Therefore, the development loop has been relatively short, and most of the modifications and improvements have been made to satisfy the needs of the developers themselves.
    Description: Italian Presidenza del Consiglio dei Ministri, Dipartimento della Protezione Civile (DPC).
    Description: Published
    Description: 495-504
    Description: 4.2. TTC - Modelli per la stima della pericolosità sismica a scala nazionale
    Description: JCR Journal
    Description: restricted
    Keywords: Seismic Hazard ; Seismology ; Probabilistic Seismic Hazard Assesment ; PSHA ; 04. Solid Earth::04.06. Seismology::04.06.02. Earthquake interactions and probability ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion ; 04. Solid Earth::04.06. Seismology::04.06.11. Seismic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 7
    Publication Date: 2020-10-26
    Description: One of the main objectives of the ITACA (ITalian ACcelerometric Archive) strong motion database, promoted by the Italian Department of Civil Protection, was to improve the characterization of the recording sites from a geological and geophysical point of view and to provide their seismic classification according to the seismic norms pertinent to Italy, namely the Eurocode 8 and the National Technical Norms for Constructions. A standard format to summarize the available information for the recording stations was first produced, in terms of a technical report dynamically linked to the database, i.e., some of the relevant information is automatically updated when the corresponding fields of the database are modified. Then, an important activity of collection, qualification and synthesis of available data was carried out, especially for stations that recorded the strongest earthquakes in Italy in the last 40 years, and for which a relevant number of studies have been published. In spite of this activity, among the more than 700 strong motion stations present in the ITACA database, only a limited number of them could be characterized by quantitative information on subsurface soil properties. For this reason, a dual seismic site classification criterion was implemented, either based on the standard Vs,30 scheme, or, in the absence of such information, based on an expert opinion supported by shallow geology maps, mostly at 1:100,000 scale, and when available on the H/V ratios calculated on recordings. Owing to the relevance in the Italian geographic and morphological context, a special care was also given to the topographic classification of stations, based on suitable criteria developed within a GIS environment.
    Description: Published
    Description: 1779-1796
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: open
    Keywords: ITACA database ; Strong motion station ; General characterization ; Site classification ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring ; 05. General::05.02. Data dissemination::05.02.02. Seismological data ; 05. General::05.09. Miscellaneous::05.09.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 8
    Publication Date: 2017-04-04
    Description: Abstract We critically analyze the results on seismic intensity attenuation in Italy derived by Albarello and D’Amico (2004) and Gasperini (2001).We demonstrate that, due to the inadequacy of certain underlying assumptions, the empirical relationships determined in those studies did not best reproduce the decay of intensity as the distance from the source increases. We reconsidered some of the relevant concepts and assumptions used in these intensity-attenuation studies (macroseismic epicenter, epicentral intensity, data completeness) to suggest some useful recipes for obtaining unbiased estimates. In particular, we suggest that (1) data for distances from the source at which an intensity below the limit of diffuse perceptibility (≤IV) is expected should be excluded from attenuation computations because such data are clearly incomplete, (2) attenuation equations that include a term proportional to the epicentral intensity I0 with a coefficient different from 1.0 must not be used because they imply a variable offset between I0 and the intensity expected at the epicenter, and (3) epicentral intensities must be recomputed consistently with the attenuation equation because those reported by the Italian catalog do not generally correspond with the intensity predicted at the epicenter by the attenuation relationships so far proposed. Following these suggestions produces a significant reduction in the standard deviation of the model that might lead to a corresponding reduction of the estimates of seismic hazard.
    Description: Published
    Description: 682-691
    Description: JCR Journal
    Description: reserved
    Keywords: Macroseismic intensity, Ground motion equation ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 9
    Publication Date: 2017-04-04
    Description: Previous works based mainly on strong-motion recordings of large Japanese earthquakes showed that site amplification and soil fundamental frequency could vary over long and short time scales. These phenomena were attributed to non-linear soil behaviour: the starting fundamental frequency and amplification were both instantaneously decreasing and then recovering for a time varying from few seconds to several months. The recent April 6, 2009 earthquake (M W 6.3), occurred in the L’Aquila district (central Italy), gave us the possibility to test hypotheses on time variation of amplification function and soil fundamental frequency, thanks to the recordings provided by a pre-existing strong-motion array and by a large number of temporary stations. We investigated the intra- and inter-event soil frequency variations through different spectral analyses, including time-frequency spectral ratios and S-Transform (Stockwell et al. in IEEE Trans Signal Process 44:998–1001, 1996). Finally, analyses on noise recordings were performed, in order to study the soil behaviour in linear conditions. The results provided puzzling evidences. Concerning the long time scale, little variation was observed at the permanent stations of the Aterno Valley array. As for the short time-scale variation, the evidence was often contrasting, with some station showing a time-varying behavior, while others did not change their frequency with respect to the one evaluated from noise measurements. Even when a time-varying fundamental frequency was observed, it was difficult to attribute it to a classical, softening non-linear behaviour. Even for the strongest recorded shocks, with peak ground acceleration reaching 0.7 g, variations in frequency and amplitude seems not relevant from building design standpoint. The only exception seems to be the site named AQV, where the analyses evidence a fundamental frequency of the soil shifting from 3 Hz to about 1.5 Hz during the mainshock.
    Description: Published
    Description: 869-892
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: open
    Keywords: Strong motion ; Subsoil non-linearity ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
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  • 10
    Publication Date: 2017-04-04
    Description: We exploit S-wave spectral amplitudes from 112 aftershocks (3.0 ≤ ML ≤ 5.3) of the L’Aquila 2009 seismic sequence recorded at 23 temporary stations in the epicentral area to estimate the source parameters of these events, the seismic attenuation characteristics and the site amplification effects at the recording sites. The spectral attenuation curves exhibit a very fast decay in the first few kilometers that could be attributed to the large attenuation of waves traveling trough the highly heterogeneous and fractured crust in the fault zone of the L’Aquila mainshock. The S-waves total attenuation in the first 30 km can be parameterized by a quality factor QS(f) = 23f^0.58 obtained by fixing the geometrical spreading to 1/R. The source spectra can be satisfactorily modeled using the omega-square model that provides stress drops between 0.3 and 60 MPa with a mean value of 3.3±2.8 MPa. The site responses show a large variability over the study area and significant amplification peaks are visible in the frequency range from 1 to more than 10 Hz. Finally, the vertical component of the motion is amplified at a number of sites where, as a consequence, the horizontal-to-vertical spectral ratios (HVSR) method fails in detecting the amplitude levels and in few cases the resonance frequencies.
    Description: Published
    Description: 717-739
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: reserved
    Keywords: Generalized Inversion Technique ; 2009 L'Aquila earthquake ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
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  • 11
    Publication Date: 2017-04-04
    Description: The selection of specific elastic response spectra according to soil categories is the easiest way to account for site effects in engineering projects and general-purpose hazard maps. Most of the international seismic codes make use of the average shear wave velocity of the upper 30 m (Vs,30) to discriminate soil categories, although some doubts arose about the capability of Vs,30 to predict actual soil amplification. In this work we propose two soil classifications in which the soil fundamental frequency (f0) becomes either an alternative or a complement to Vs,30. The performance of the derived categorizations is achieved through the estimation of the standard deviation associated to ground motion prediction equations of acceleration response spectra, considering recordings extracted from the Italian strong motion data base. The results indicate that there is a significant reduction of the standard deviation when the classification is based on the couple of variables Vs,30–f0, although a classification based of the single f0 also leads to satisfactory results, comparable with those obtained assuming a classification scheme based on Vs,30.
    Description: Published
    Description: 1877-1898
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: reserved
    Keywords: site effects ; soil classification ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
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  • 12
    Publication Date: 2020-02-24
    Description: The S1 pecial Issue of the Bulletin of Earthquake Engineering devoted to the new 2 Italian strong motion database ITACA (ITalian ACelerometric Archive) is introduced in this 3 foreword. An overview of the papers published in this issue is presented, providing an idea of 4 the number of problems encountered in the compilation of a database as rich of information 5 as ITACA, of the solutions adopted and of the possible research and practical applications. 6 Most of the contents, though specifically addressed to ITACA and to its accelerograms, can 7 be usefully thought of as an exemplification of approaches and methods that can be used for, 8 and extended to, similar databases in other countries
    Description: Published
    Description: 1717-1721
    Description: 5.2. TTC - Banche dati di sismologia strumentale
    Description: JCR Journal
    Description: reserved
    Keywords: Strong motion database ; ITACA ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
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  • 13
    Publication Date: 2017-04-04
    Description: We have studied two velocity-depth models with the aim of outlining the behavior of a velocity reversal in the top layer, which is associated with the stiff Brecce de L’Aquila unit (BrA). In this setting, the SMTH model is topped by a layer with about 2:1 impedance contrast with the underlying layer while the NORV model has no velocity reversal. We have simulated the propagation of SH and P-SV wavefields in the range 0–10 Hz for incidence 0◦ –90◦ . Earthquake spectral ratios of the horizontal and vertical components at six sites in L’Aquila downtown are compared to corresponding syn- thetics spectral ratios. The vertical component of P-SV synthetics enables us to investigate a remarkable amplification effect seen in the vertical component of the recorded strong motion. Sites AQ04 and AQ05 are best matched by synthetics from the NORV model while FAQ5 and AQ06 have a better match with synthetics spectral ratios from the SMTH model. All simulations show this behavior systematically, with horizontal and near-horizontal incident waves predicting the overall pattern of matches more clearly than vertical and near-vertical incidence. The model inferences are in agreement with new geological data reporting lateral passages in the top layer from the stiff BrA to softer sediments. Matches are good in terms of frequency of the first amplification peak and of spectral amplitude: the horizontal compo-nents have spectral ratio peaks predominantly at 0.5 Hz in the simulations and at 0.7 Hz in the data, both with amplitudes of 4, while the vertical component spectral ratios reach values of 6 at frequencies of about 1 Hz in both data and simulations. The vertical component spectral ratios are very well matched using Rayleigh waves with incidence at 90◦ . The NORV model without the velocity reversal predicts spectral ratio peaks for the horizontal components at frequencies up to 6 Hz. The reversal of velocity acts as a low-pass frequency filter on the horizontal components reducing the amplification effect of the sediment filled valley.
    Description: Published
    Description: 761-781
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: reserved
    Keywords: site effect, 2D synthetic seismograms, spectral ratios, reversal of velocity, L'Aquila ; 01. Atmosphere::01.02. Ionosphere::01.02.05. Wave propagation ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 14
    Publication Date: 2017-04-04
    Description: Abstract Several different attenuation models have recently been proposed for the Italian region to characterize the decay of macroseismic intensity with the distance from the source. The significant scatter between these relationships and some significant drawbacks that seem to characterize previous approaches (described in a companion article by Pasolini et al., 2008) suggest that the problem needs to be reconsidered. As a first step toward more detailed analyses in the future, this study aimed at developing an isotropic attenuation relationship for the Italian area. Because this attenuation relationship has to be used primarily in probabilistic seismic hazard assessment, major attention was given to evaluating the attenuation relationship in its complete probabilistic form. Another important aspect of this study was the preliminary evaluation of the intrinsic (i.e., independent of the specific attenuation relationship to be used) scattering of data, which represents the lowest threshold for the residual variance that cannot be explained by the attenuation relationship. Furthermore, the peculiar formal features of intensity data and relevant uncertainties were considered carefully. To reduce possible biases, the completeness of the available database was checked and a suitable data selection procedure was applied. Since epicentral intensity cannot be defined unambiguously from the experimental point of view, the attenuation relationship was scaled with a new variable that is more representative of the earthquake dimension. Several criteria were considered when evaluating competing attenuation formulas (explained variance, Bayesian information criteria, Akaike information criteria, etc.). Statistical uncertainty about empirical parameters was evaluated by using standard approaches and bootstrap simulations. The performance of the selected relationship with respect to a control sample was analyzed by using a distribution-free approach. The resulting equation for the expected intensity I at a site located at epicentral distance R is I IE 0:0086 0:0005 D h 1:037 0:027 ln D ln h ; where D R2 p h2, h 3:91 0:27 km, and IE is the average expected intensity at the epicenter for a given earthquake that can be computed from the intensity data (when available) or by using empirical relationships with the moment magnitude Mw or the epicentral intensity I0 reported by the Italian seismic catalog IE 5:862 0:301 2:460 0:055 Mw; IE 0:893 0:254 1:118 0:033 I0: Comparison of the model standard deviation (S.D.) (0.69 intensity degrees) with the intrinsic one (0.62) indicates that this attenuation equation is not far from being optimal.
    Description: Published
    Description: 692-708
    Description: JCR Journal
    Description: reserved
    Keywords: Macroseismic intensity, Ground motion prediction equation ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
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  • 15
    Publication Date: 2017-04-04
    Description: On 6 April 2009, an earthquake of Mw 6:13 (Herrmann et al., 2011) occurred in central Italy, close to the town of L’Aquila. Although the earthquake is considered to be a moderate-size event, it caused extensive damage to the surrounding area. The earthquake is identified with significant directivity effects: highamplitude, short-duration motions are observed at the stations that are oriented along the rupture direction, whereas low-amplitude, long-duration motions are observed at the stations oriented in the direction opposite to the rupture. The complex nature of the earthquake combined with its damage potential brings the need for studies that assess the seismological characteristics of the 2009 L’Aquila mainshock. In this study, we present the strong-ground-motion simulation of this particular earthquake using a stochastic finite-fault model with a dynamic corner frequency approach. For modeling the resulting ground motions, we choose two finite-fault source models that take into account the source complexity of the L’Aquila mainshock. In order to test the sensitivity of ground-motion parameters to the seismic wave attenuation parameters, we use two different attenuation models obtained in the study region using weak-motion and strong-motion databases. Comparisons are made between the attenuation of synthetics and ground-motion prediction equations (GMPEs). Synthetic ground motions are further compared with the observed ones in terms of Fourier amplitude and response spectra at 21 strong-ground-motion stations that recorded the mainshock within an epicentral distance of 100 km. The spatial distribution of shaking intensity obtained from the “Did You Feel It?” project and site survey results are compared with the spatial distributions of simulated peak ground-motion intensity parameters. Our results show that despite the limitations of the method in simulating the directivity effects, the stochastic finite-fault model seems an effective and fast tool to simulate the high-frequency portion of ground motion.
    Description: Published
    Description: 1429-1445
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: restricted
    Keywords: 2009 L'Aquila sequence ; strong ground motion simulations ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 16
    Publication Date: 2022-05-24
    Description: The 2009 Mw 6.3 L’Aquila event caused extensive damage in the city of L’Aquila and in some small towns in its vicinity. The most severe damage was recognized SE of L’Aquila town along the Aterno river valley. Although building vulnerability and near-source effects are strongly responsible for the high level of destruction, site effects have been invoked to explain the damage heterogeneities and the similarities between the 2009 macroseismic field with the intensities of historical earthquakes. The small village of Onna is settled on quaternary alluvium and suffered during the L’Aquila event an extremely heavy damage in the masonry structures with intensity IX–X on the Mercalli-Cancani-Sieberg (MCS) scale. The village of Monticchio, far less than 1.3 km from Onna, is mostly situated on Meso- zoic limestone and suffered a smaller level of damaging (VI MCS). In the present paper, we analyze the aftershock recordings at seismic stations deployed in a small area of the middle-Aterno valley including Onna and Monticchio. The aim is to investigate local ampli-fication effects caused by the near-surface geology. Because the seismological stations are close together, vulnerability and near-source effects are assumed to be constant. The wave- form analysis shows that the ground motion at Onna is systematically characterized by large high-frequency content. The frequency resonance is varying from 2 to 3 Hz and it is related to alluvial sediments with a thickness of about 40 m that overlay a stiffer Pleistocene substrate. The ground motion recordings of Onna are well reproduced by the predictive equation for the Italian territory.
    Description: Published
    Description: 783-807
    Description: 2T. Sorgente Sismica
    Description: JCR Journal
    Description: reserved
    Keywords: L’Aquila 2009 earthquake · Site effects · Onna · Seismic microzoning · Ground motion prediction equations ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 17
    Publication Date: 2023-06-05
    Description: A detailed analysis of the earthquake effects on the urban area of Rome has been conducted for the L’Aquila sequence, which occurred in April 2009, by using an on-line macroseismic questionnaire. Intensity residuals calculated using the mainshock and four aftershocks are analyzed in the light of a very accurate and original geological reconstruction of the subsoil of Rome based on a large amount of wells. The aim of this work is to highlight ground motion amplification areas and to find a correlation with the geological settings at a sub-regional scale, putting in evidence the extreme complexity of the phenomenon and the difficulty of making a simplified model. Correlations between amplification areas and both near-surface and deep geology were found. Moreover, the detailed scale of investigation has permitted us to find a correlation between seismic amplification in recent alluvial settings and subsiding zones, and between heard seismic sound and Tiber alluvial sediments.
    Description: Published
    Description: 425-443
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: open
    Keywords: Earthquakes ; Intensity residuals ; Urban geosciences ; Macroseismic effects ; Amplification areas ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion ; 04. Solid Earth::04.06. Seismology::04.06.11. Seismic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 18
    Publication Date: 2012-02-03
    Description: The Italian strong-motion database was created during a joint project between Istituto Nazionale di Geofisica e Vulcanologia (INGV, Italian Institute for Geophysics and Vulcanology) and Dipartimento della Protezione Civile (DPC, Italian Civil Protection). The aim of the project was the collection, homogenization and distribution of strong motion data acquired in Italy in the period 1972–2004 by different institutions, namely Ente Nazionale per l’Energia Elettrica (ENEL, Italian electricity company), Ente per le Nuove tecnologie, l’Energia e l’Ambiente (ENEA, Italian energy and environment organization) and DPC. Recently the strong-motion data relative to the 23th December 2009, Parma (Mw = 5.4 and Mw = 4.9) and to the April 2009 L’Aquila sequences (13 earthquakes with 4.1 ≤ Mw ≤ 6.3) were included in the Italian Accelerometric Archive (ITACA) database (beta release). The database contains 7,038 waveforms from analog and digital instruments, generated by 1.019 earthquakes with magnitude up to 6.9 and can be accessed on-line at the web site http://itaca. mi.ingv.it. The strong motion data are provided in the unprocessed and processed versions. This article describes the steps followed to process the acceleration time series recorded by analogue and digital instruments. The procedures implemented involve: baseline removal, instrumental correction, band pass filtering with acausal filters, integration of the corrected acceleration in order to obtain velocity and displacement waveforms, computation of accel- eration response spectra and strong motion parameters. This procedure is applied to each accelerogram and it is realised to preserve the low frequency content of the records.
    Description: Published
    Description: 1175-1187
    Description: 5.2. TTC - Banche dati di sismologia strumentale
    Description: JCR Journal
    Description: open
    Keywords: Strong motion ; processing ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 19
    Publication Date: 2017-04-04
    Description: The Italian Accelerometic Archive (ITACA) was created in 2007 during a joint project between the Italian Institute for Geophysics and Vulcanology (Istituto Nazionale di Geofisica e Vulcanologia, INGV) and the Italian Civil Protection (Dipartimento della Protezione Civile, DPC). The project, started in 2006, had the aim of filling the data gap of existing strong motion databases and facilitating strong motion data users in obtaining good quality waveforms, through the collection, homogenization and distribution of strong motion data acquired during the period 1972–2004 in Italy by different institutions (Ente Nazionale per l’Energia Elettrica, ENEL, Italian electricity company; Ente per le Nuove tecnologie, l’Energia e l’Ambiente, ENEA, Italian energy and environment organizationDPC). The compiled database contains 2,182 three-component waveforms generated by 1,008 earthquakes with a maximum moment magnitude of 6.9 (1980 Irpinia earthquake) and can be accessed on-line at the portal denominated ITACAat the site http://itaca.mi.ingv.it,where a wide range of search tools enables the user to interactively retrieve events, recording stations and waveforms with particular characteristics, whose parameters can be specified, as needed, through user friendly interfaces. A range of display options allows users to view data in different contexts, extract and download time series and spectral data. This article describes the state of the art up to 2006 and the activities which led to the completion of the project.
    Description: Published
    Description: 1159-1174
    Description: 5.2. TTC - Banche dati di sismologia strumentale
    Description: JCR Journal
    Description: open
    Keywords: strong motion ; database ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 20
    Publication Date: 2017-04-04
    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
    Keywords: Irpinia 1980 earthquake ; ground-motion simulation ; ground-motion variability ; scenario events ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 21
    Publication Date: 2017-04-04
    Description: Italy is a country characterized by high seismic hazard so strong-motion monitoring represents a relevant issue. Several strong-motion networks have been installed in the Italian territory during the last decades, with the aim of recording the ground motion generated by moderate to strong events or to monitor single regions. The collection of the strong-motion recordings of the Italian earthquakes was recently fulfilled and data are distributed through the ITACA database (http://itaca.mi.ingv.it). The new data set was used to develop a set of ground motion prediction equations (hereinafter GMPEs) for the Italian territory (Bindi et al., 2009), in order to update the well known GMPEs developed by Sabetta and Pugliese. The recent Mw 6.3 earthquake that occurred in central Italy on April 2009 and the upgrades of the ITACA database gave us the possibility to validate the predictive capability of the newly developed GMPEs and to explore the regional variability inside the Italian territory.
    Description: Published
    Description: 53-70
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: reserved
    Keywords: strong motion data ; Prediction equation ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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  • 22
    Publication Date: 2017-04-04
    Description: A temporary network of 33 seismic stations was deployed in the area struck by the 6th April 2009, Mw 6.3, L’Aquila earthquake (central Italy), with the aim to investigate the site amplification within the Aterno river Valley. The seismograms of 18 earthquakes recorded by 14 of the 33 stations were used to evaluate the average horizontal to vertical spectral ratio (HVSR) for each site and the standard horizontal spectral ratio (SSR) between a site and a reference station. The obtained results have been compared to the geological and geophysical information in order to explain the resonance frequencies and the amplification levels with respect to surface geology of the valley. The result indicate that there is no uniform pattern of amplification, due to the complex geologic setting, as the thickness and degree of cementation of the deposits is highly variable. As consequence, a large number of the local site response is observed, therefore it is very difficult to elaborate a unique model that can explain such a variability of the amplification.
    Description: Published
    Description: 697-715
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: partially_open
    Keywords: l'Aquila earthquake ; microzoning ; ground shaking ; site effects ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 23
    Publication Date: 2022-05-24
    Description: The April 6, 2009 L’Aquila earthquake was responsible for an “anomalous”, relatively high degree of damage (i.e. Is 7 MCS scale) at Castelvecchio Subequo (CS). Indeed, the village is located at source-to-site distance of about 40 km, and it is surrounded by other inhabited centres to which considerably lower intensities, i.e. Is 5-6, have been attributed. Moreover, the damage was irregularly distributed within CS, being mainly concentrated in the uppermost portion of the old village. Geophysical investigations (ambient seismic noise and weak ground motions analyses) revealed that site effects occurred at CS. Amplifications of the ground motion, mainly striking NE-SW, have been detected at the uppermost portion of the carbonate ridge on which the village is built. Geological/structural and geomechanical field surveys defined that the CS ridge is affected by sets of fractures, joints and shear planes – mainly roughly NW-SE and N-S trending – that are related to the deformation zone of the Subequana valley fault system and to transfer faults linking northward the mentioned tectonic feature with the Middle Aterno Valley fault system. In particular, our investigations highlight that seismic amplifications occur where joints set NW-SE trending are open. On the other hand, no amplification is seen in portions of the ridge where the bedrock is densely fractured but no open joints occur. The fracture opening seems related to the toppling tendency of the bedrock slabs, owing to the local geomorphic setting. These investigations suggest that the detected amplification of the ground motion is probably related to the polarization of the seismic waves along the Castelvecchio Subequo ridge, with the consequent oscillation of the rock slabs perpendicularly to the fractures azimuth.
    Description: Published
    Description: 841-868
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: open
    Keywords: Site effects ; Rock site ; Ambient seismic noise ; Structural characteristics ; Geomechanical analyses ; Jointing ; Castelvecchio Subequo ; 2009 L'Aquila earthquake ; central Italy ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 24
    Publication Date: 2017-04-04
    Description: Seismograms from 55 intermediate-depth Vrancea earthquakes (M 4:0– 7:1) recorded at 43 stations of an accelerometric network in Romania are used to derive source spectra and site amplification functions from S waves in the frequency range 0.5–20 Hz with the generalized inversion technique (GIT) (Castro et al., 1990). Attenuation is taken into account using the nonparametric attenuation functions derived by Oth et al. (2008) from the same dataset, and the attenuation-corrected data are then split into source and site contributions. The source spectra follow the ω 2 model (Brune, 1970, 1971) with high corner frequencies and a related Brune stress drop of the order of 100 MPa. The site amplification functions are separately determined for both horizontal and vertical components. Contrary to widespread expectation, the vertical component shows significant amplification effects at high frequencies. The H=Z ratios determined from the GIT results compare well with H=V ratios computed directly from the S-wave window of the accelerograms (Lermo and Chávez-García, 1993). The basic assumption for the determination of site effects from H=V ratios is that the vertical component is not or only little affected by site effects. For Vrancea earthquakes, this assumption is incorrect; consequently, site effects should not be estimated from H=V ratios. The reason for this peculiar fact is the geometry of intermediate-depth seismicity that leads to almost vertical ray paths beneath the stations.
    Description: Published
    Description: 235-254
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: open
    Keywords: source spectra ; Vrancea region ; site effects ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 25
    Publication Date: 2017-04-04
    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
    Keywords: ground-motion simulation ; Gubbio 1984 ; ground-motion variability ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
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  • 26
    Publication Date: 2017-04-04
    Description: Moderate-magnitude shallow earthquakes in the Atlantic Ocean, hundreds of kilometres southwest of Lisbon, can generate efficient suboceanic Rayleigh waves (SRW) that are well recorded in Portugal. Here we compare moderate-size earthquakes recorded by seismic stations in Portugal with the Tyrrhenian Sea earthquakes recorded in peninsular Italy where SRW were recently observed. In spite of a different behaviour of high frequencies due to the different tectonic setting of the two areas, similar results are found in the intermediate-period range, suggesting that this effect, if extrapolated to a magnitude larger than 8, could be devastating at regional distance in terms of ground motion amplitude and duration. Through 1D models, we explore the hypothesis that the high level of destruction and the long duration of shaking felt during the Great 1755 Lisbon earthquake were caused by SRW. In this preliminary study, we check the role of critical model parameters. We find that duration and amplitude are largest when the average thickness of the water layer is 2 km and shear-wave velocity of the ocean floor is close to the speed of sound in the water. Both conditions are realistic for a source in the Atlantic Ocean, few hundreds of kilometres southwest of Lisbon. Moreover, the propagation of SRW at regional distances accounts for durations of more than ten minutes as the effect of a single large earthquake.
    Description: Published
    Description: 283-295
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: open
    Keywords: ground motion ; surface waves ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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  • 27
    Publication Date: 2017-04-04
    Description: Experimental data and numerical modelling were used to study the effect of local geology on the seismic response of the Catania area. The town extends on a marly clays bedrock and terraced deposits made up by coastal sands and alluvial conglomerates. This sedimentary substratum is deeply entrenched by paleo-valleys filled by lava flows and pyroclastics. Available borehole data and elastic parameters were used to reconstruct a geotechnical model in order to perfome 1D numerical modeling. Seismic urban scenarios were simulated considering destructive (Mw = 7.0), strong (Mw = 6.2) and moderate (Mw = 5.7) earthquakes to assess the shaking level of the different outcropping formations. For each scenario seven real accelerograms were selected from the European Strong Motion Database to assess the expected seismic input at the bedrock. PGA and spectral acceleration at different periods were obtained in the urban area through the equivalent linear numerical code EERA, and contour maps of different levels of shaking were drawn. Standard and horizontal-to-vertical spectral ratios were achieved making use of a dataset of 172 seismic events recorded at ten sites located on the main outcropping lithotypes. Spectral ratios inferred from earthquake data were compared with theoretical transfer functions. Both experimental and numerical results confirm the role of the geological and morphologic setting of Catania. Amplification of seismic motion mainly occurs in three different stratigraphic conditions: (a) sedimentary deposits mainly diffused in the south of the study area; (b) spots of soft sediments surrounded by lava flows; (c) intensely fractured and scoriaceous basaltic lavas.
    Description: In press
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: restricted
    Keywords: Scenario earthquake ; 1D modelling ; PGA values ; Earthquake records ; spectral ratios ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis
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  • 28
    Publication Date: 2021-06-21
    Description: Probabilistic seismic hazard analysis is currently the soundest basis for the rational evaluation of ground-motion hazard for site-specific engineering design and assessment purposes. An increasing number of building codes worldwide acknowledge the uniform hazard spectra as the reference to determine design actions on structures and to select input ground motions for seismic structural analysis. This is the case, for example, in Italy where the new seismic code also requires the seismic input for nonlinear dynamic analysis to be selected on the basis of dominating events, for example, identified via disaggregation of seismic hazard. In the present study, the design earthquakes expressed in terms of representative magnitude (M), distance (R), and ε were investigated for a wide region in the southern Apennines, Italy. To this aim, the hazards corresponding to peak ground acceleration and spectral acceleration at 1 sec with a return period of 475 yr were disaggregated. For each of the disaggregation variables the shape of the joint and marginal probability density functions were studied. The first two modes expressed by M, R, and ε were extracted and mapped for the study area. The results shown provide additional information, in terms of source and ground-motion parameters, to be used along with the standard hazard maps to better select the design earthquakes. The analyses also allow us to assess how various frequency ranges of the design spectrum are differently contributed by seismic sources in the study area.
    Description: Published
    Description: 2979–2991
    Description: 4.2. TTC - Modelli per la stima della pericolosità sismica a scala nazionale
    Description: JCR Journal
    Description: reserved
    Keywords: seismic hazard ; disaggregation ; Southern Apenniens ; design earthquake ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion ; 04. Solid Earth::04.06. Seismology::04.06.11. Seismic risk
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  • 29
    Publication Date: 2020-11-16
    Description: Geological, geophysical and geotechnical investigations, for the characterization of the strong-motion recording sitesmanaged by the ItalianCivil Protection, have been carried out in the framework of the project “Italian strong-motion database in the period 1972–2004”. The project aimed at creating an updated database of strong-motion data acquired in Italy by different institutions in the time span 1972–2004, and at improving the quality of disseminated data. This article illustrates the state of the recording site characterization before the beginning of the project, explains the criteria adopted to select the sites where geophysical/ geotechnical investigation have been performed and describes the results of the promoted field surveys.
    Description: Published
    Description: 1189–1207
    Description: 4IT. Banche dati
    Description: JCR Journal
    Description: open
    Keywords: site ; characterization ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
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  • 30
    Publication Date: 2017-04-04
    Description: The Italian strong-motion database was created during a joint project between Istituto Nazionale di Geofisica e Vulcanologia (INGV, Italian Institute for Geophysics and Vulcanology) and Dipartimento della Protezione Civile (DPC, Italian Civil Protection). The aim of the project was the collection, homogenization and distribution of strong motion data acquired in Italy in the period 1972-2004 by different institutions, namely Ente Nazionale per l’Energia Elettrica (ENEL, Italian electricity company), Ente per le Nuove tecnologie, l’Energia e l’Ambiente (ENEA, Italian energy and environment organization) and DPC. Recently the strong-motion data relative to the 23th December 2009, Parma (Mw=5.4 and Mw=4.9) and to the 2009 L’Aquila sequence (13 earthquakes with 4.1Mw6.3) were included in the ITACA database (beta release). The database contains 7038 waveforms from analog and digital instruments, generated by 1019 earthquakes with magnitude up to 6.9 and can be accessed on-line at the web site http://itaca.mi.ingv.it. The strong motion data are provided in the unprocessed and processed versions. This article describes the steps followed to process the acceleration time series recorded by analogue and digital instruments. The procedures implemented involve: baseline removal, instrumental correction, band pass filtering with acausal filters, integration of the corrected acceleration in order to obtain velocity and displacement waveforms, computation of acceleration response spectra and strong motion parameters. This procedure is applied to each accelerogram, is realised to preserve the low frequency content of the records.
    Description: In press
    Description: 5.2. TTC - Banche dati di sismologia strumentale
    Description: JCR Journal
    Description: open
    Keywords: strong-motion ; processing ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 31
    Publication Date: 2017-04-04
    Description: A revised Italian strong motion archive has become available since July 2007, including all the records of the strongest events occurred from 1972 to 2004. It contains the uncorrected and corrected accelerograms and the metadata relevant to seismic events, recording stations and instruments added after a careful revision. The availability of this archive allowed us to perform a first step towards an update of the reference ground motion prediction equations for Italy, which were evaluated by Sabetta and Pugliese in (Bull Seismol Soc Am 77:1491–1513, 1987), for peak ground acceleration and velocity, and subsequently extended to the 5% damped pseudovelocity response spectra in 1996. A subset with the 27 major earthquakes occurred in Italy from 1972 to 2002, in the magnitude range 4.6–6.9, was extracted and 235 good quality waveforms were selected, recorded at distances up to 183 km. The goodness of fit of the Sabetta and Pugliese (Bull Seismol Soc Am 86:337–352, 1996) model was explored using two independent statistical approaches (Spudich et al. Bull Seismol Soc Am 89:1156–1170, 1999 and Scherbaum et al. Bull Seismol Soc Am 94:2164– 2185, 2004). The results obtained show that the Sabetta and Pugliese (Bull Seismol Soc Am 77:1491–1513, 1987) does not adequately fit the new strong-motion data set, for its small standard deviation and its non-zero bias. In particular, the most noteworthy result is that the Sabetta and Pugliese (Bull Seismol Soc Am 77:1491–1513, 1987) over-predicts peak ground acceleration and velocity at rock sites. New coefficients for the prediction of horizontal peak ground acceleration, peak ground velocity and acceleration response spectra, adopting the same functional form in Sabetta and Pugliese (Bull Seismol Soc Am 77:1491–1513, 1987), were then evaluated in order to fit the new data set. This paper illustrates the steps made to update the existing ground motion prediction equations for Italy, discusses their limitations and provides the basis for future developments.
    Description: Published
    Description: 591–608
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: reserved
    Keywords: ground motion prediction ; equation ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 32
    Publication Date: 2017-04-04
    Description: The Italian Accelerometic Archive (ITACA) was created in 2007 during a joint project between the Italian Institute for Geophysics and Vulcanology (Istituto Nazionale di Geofisica e Vulcanologia, INGV) and the Italian Civil Protection (Dipartimento della Protezione Civile, DPC). The project, started in 2006, had the aim of filling the data gap of existing strong motion databases and facilitating strong motion data users in obtaining good quality waveforms, through the collection, homogenization and distribution of strong motion data acquired during the period 1972-2004 in Italy by different institutions (Ente Nazionale per l’Energia Elettrica, ENEL, Italian electricity company; Ente per le Nuove tecnologie, l’Energia e l’Ambiente, ENEA, Italian energy and environment organization DPC). The compiled database contains 2182 three-component waveforms generated by 1008 earthquakes with a maximum moment magnitude of 6.9 (1980 Irpinia earthquake) and can be accessed on-line at the portal denominated ITACA at the site http://itaca.mi.ingv.it, where a wide range of search tools enables the user to interactively retrieve events, recording stations and waveforms with particular characteristics, whose parameters can be specified, as needed, through user friendly interfaces. A range of display options allows users to view data in different contexts, extract and download time series and spectral data. This article describes the state of the art up to 2006 and the activities which led to the completion of the project.
    Description: In press
    Description: 5.2. TTC - Banche dati di sismologia strumentale
    Description: JCR Journal
    Description: open
    Keywords: strong-motion ; database ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 33
    Publication Date: 2017-04-04
    Description: A set of Ground Motion Prediction Equations (GMPEs) for the Italian territory is proposed, exploiting a new strong-motion data set become available since July 2007 through the Italian Accelerometric Archive (ITACA). The data set is composed by 561 three-component waveforms from 107 earthquakes with moment magnitude in the range 4.0–6.9, occurred in Italy from 1972 to 2007 and recorded by 206 stations at distances up to 100 km. The functional form used to derive GMPEs in Italy (Sabetta and Pugliese in Bull Seismol Soc Am 86(2):337–352, 1996) has been modified introducing a quadratic term for magnitude and a magnitude-dependent geometrical spreading. The coefficients for the prediction of horizontal and vertical peak ground acceleration, peak ground velocity and 5% damped acceleration response spectra are evaluated. This paper illustrates the new data set, the regression analysis and the comparisons with recently derived GMPEs in Europe and in the Next Generation Attenuation of Ground Motions (NGA) Project.
    Description: In press
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: open
    Keywords: ground motion ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 34
    Publication Date: 2017-04-04
    Description: In this study we investigate the site amplification effects observed in the Gubbio plain, central Italy. The recordings of 140 local earthquakes (1:2 ≤ Ml ≤ 4:7) observed by two linear arrays installed along the longitudinal and perpendicular basin axis are analyzed both in the time and frequency domains to determine the spatial variation of the local site effects in the basin. The time series recorded in the Gubbio plain are characterized by locally generated surface waves, which cause a significant increase in both ground-motion duration and amplitude with respect to a nearby reference station on a rock site. In the middle of the basin where the sedimentary cover is thickest (ca 600 m), the peak ground velocity is amplified on average by a factor of 5 with respect to the reference station installed on rock, and the duration is increased by a factor of about 2. The analyses in the frequency domain show that the spectral energy of the basin-generated waves is mainly distributed over the range 0.4–2 Hz and affects both horizontal and vertical components. The site responses estimated by applying two reference site methods show that the overall shape of the amplification functions is similar for the sites located inside the basin with a difference in the amplification levels, which can reach values as high as 30 in the middle of the valley. Amplifications up to a factor of 10 affect the vertical component of ground motion over a broad frequency range for nearly all basin sites with the maximum amplifications occurring at around 1 Hz. Finally, although the horizontal-to-vertical spectral ratios were found to provide a reliable estimation of the fundamental resonance frequency of the site, they fail to estimate the shape of the site transfer function
    Description: Published
    Description: 741–760
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: reserved
    Keywords: site amplification ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 35
    Publication Date: 2017-04-04
    Description: The interevent and interstation ground-motion variability of the updated Italian strong-motion database (Italian Accelerometric Archive [ITACA]) has been explored through the development of new empirical ground-motion prediction equations (GMPEs) for Italy. The regressions have been performed on 241 three-component waveforms from 27 earthquakes with moment magnitudes ranging from 4.8 to 6.9, recorded by 146 stations at distances up to 200 km. The site classification follows the schemes previously proposed for Italy, in which two soil classes are defined, considering both shear-wave velocity and deposit thickness. The regression analysis uses the values of the explanatory variables (magnitude, fault distance, site class, and style of faulting) recently revised in the framework of a project funded by the Italian Department of Civil Protection. The equations have been derived for peak ground acceleration, peak ground velocity, and 5% damped spectral accelerations at 18 periods from 0.03 to 2 sec. The residual variance has been decomposed into interevent, interstation, and record-to-record components by applying a random effect regression scheme. The interevent and interstation error distributions have been analyzed as function of periods to detect sites and events for which predicted values significantly deviate from observations. For periods up to 0.35 sec, the interstation is the dominant component of variance, indicating that an improvement in the site classification could lead to a refinement of the GMPEs. For longer periods, the three components of variance provide similar contributions, indicating that a reduction of the uncertainty can be achieved by reducing the epistemic uncertainty affecting the physical model. The interevent error highlights the peculiarity of few earthquakes, suggesting that the evaluation of regional GMPEs can be important when specific scenario studies should be carried out. The interstation variability allows us to detect stations with peculiar site response and to assess the goodness of the considered site classification scheme. Introduction In Italy, strong-motion recordings have been available since the early 1970s. Because different institutions managed the Italian strong-motion network (Rete accelerometrica italiana [RAN]), both waveforms and metadata needed to qualify the recordings are hardly available to end-users, except for few cases, such as the 1997–1998 Umbria-Marche sequence and the 2002 Molise earthquakes (see the Data and Resources section). The Italian Dipartimento di Protezione Civile (Italian Department for Civil Protection [DPC]) after an agreement with the Istituto Nazionale di Geofisica e Vulcanologia (Italian Institute for Geophysics and Volcanology [INGV]) funded in 2004 the project called “Database dei dati accelerometrici italiani relativi al periodo 1972–2004” (Italian strong-motion database relevant to the period 1972–2004, hereinafter referred to as project S6,
    Description: Published
    Description: 2471–2488
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: open
    Keywords: Variability ; ITACA ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
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  • 36
    Publication Date: 2017-04-04
    Description: On 6 April 2009, 01:32:40 UTC, an Mw 6.3 earthquake occurred in the Abruzzo region (central Italy), close to L’Aquila, a town of 68,500 inhabitants. About 300 people died because of the collapse of many residential and public build¬ings, and damage was widespread in L’Aquila and its neighbor¬ing municipalities. The earthquake occurred at 9.5 km depth along a NW-SW normal fault with SW dip, located below the city of L’Aquila (Istituto Nazionale di Geofisica e Vulcanologia [INGV] 2009a). The maximum observed intensity is IX–X in the MCS scale and the most relevant damages are distributed in the NW-SE direc¬tion, with evident predominance toward the southeast (Istituto Nazionale di Geofisica e Vulcanologia 2009b). This event rep¬resents the third largest earthquake recorded by strong-motion instruments in Italy, after the 1980 Mw 6.9 Irpinia and the 1976 Mw 6.4 Friuli earthquakes (Luzi et al. 2008). The mainshock was followed by seven aftershocks of moment magnitude larger than or equal to 5, the two stron¬gest of which occurred on April 7 (Mw = 5.6) and April 9 (Mw = 5.4). The mainshock and its aftershocks have been recorded by several digital stations of the Italian strong-motion network (Rete Accelerometrica Nazionale, R AN), operated by the Italian Department of Civil Protection (DPC); by the Italian seismometric network (Rete Sismometrica Nazionale, operated by INGV-Centro Nazionale Terremoti (CNT); http://cnt. rm.ingv.it); and by a temporary strong-motion array installed by the INGV Sezione di Milano-Pavia (MI-PV; http://www. mi.ingv.it). A total of 56 three-component strong-motion record¬ings were obtained within 280 km for the mainshock, with 23 being within 100 km of the epicenter. Horizontal peak ground motions in the near-fault region range from 327 to 646 cm/sec2, the latter representing one of the highest values recorded in Italy. This strong-motion data set, consisting of 954 waveforms from Mw 〉 4.0 events, is unique in Italy because it is entirely digital and includes observations from near-fault dis¬tances to some hundred kilometers away. The data set has been integrated in the new Italian strong-motion database ITACA (ITalian ACcelerometric Archive), available at http://itaca. mi.ingv.it. This paper provides an overview of the strong-motion recordings of the mainshock and the two strongest aftershocks with preliminary analyses of different strong-motion param¬eters as a function of distance, azimuth, and site conditions.
    Description: Published
    Description: 951-966
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: open
    Keywords: L'Aquila ; strong-motion ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
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  • 37
    Publication Date: 2017-04-04
    Description: The Italian strong-motion database contains 2182 three component waveforms generated by 1004 earthquakes with a maximum magnitude of 6.9 (1980 Irpinia earthquake) covering the period range from 1972 to 2004. The database is devoted to serving the seismological and engineering communities. The database can be accessed on-line at the site http://itaca.mi.ingv.it, where a wide range of search tools enables the user to interactively search events, recording stations and retrieve waveforms with particular characteristics, whose parameters can be specified, as needed, through a graphical user interface. A range of display options allows users to view data in different contexts, extract and download time series and spectral data. The database was created during a joint project between Istituto Nazionale di Geofisica e Vulcanologia (INGV, Italian institute for geophysics and vulcanology) and Dipartimento della Protezione Civile (DPC, Italian civil protection). The aim of the project was the collection, homogenization and distribution of data acquired over the time period 1972-2004 in Italy by different Italian institutions, namely Ente Nazionale per l’Energia Elettrica (ENEL, Italian electricity company), Ente per le Nuove tecnologie, l’Energia e l’Ambiente (ENEA, Italian energy and environment organization) and DPC. The project had multiple purposes, such as permanent strong motion monitoring and temporary monitoring during seismic sequences or before permanent installation. This database brings up to date the ENEA strong motion data collection which ended in 1993 and the European database where the most recent Italian data pertain to the Umbria-Marche sequence of 1997-1998 (Ambraseys at al., 2002). In addition effort was spent reviewing strong motion metadata and data processing to increase data quality and reliability. This article describes the steps that led to the completion of the project and provides an overview of the search capabilities available at the database interface website.
    Description: Published
    Description: 716-722
    Description: 5.2. TTC - Banche dati di sismologia strumentale
    Description: JCR Journal
    Description: open
    Keywords: strong-ground motion ; database ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
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  • 38
    Publication Date: 2017-04-04
    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
    Keywords: ground-motion simulation ; Gubbio 1984 ; ground-motion variability ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 39
    Publication Date: 2017-04-04
    Description: Abstract We simulated strong-motion records from the Umbria–Marche, central Italy, earthquake (Mw 6) of September 1997 using a frequency-dependent S-wave radiation function. We compared the observed acceleration spectra, from strongmotion instruments located in the near field and at regional distances, with those simulated using the stochastic modeling technique of Beresnev and Atkinson (1997, 1998), and modified to account for a frequency-dependent radiation pattern correction. By using the frequency-dependent radiation function previously obtained by Castro et al. (2006), we reduced the overall fitting error of the acceleration spectra by about 9%. In general, we observed that the frequency-dependent radiation pattern correction has a small effect on the spectral amplitudes compared with site effects, which is an important factor controlling the strong-motion records generated by the 1997 Umbria–Marche earthquake. In addition, we modeled the observed ground-motion records using the dynamic corner frequency model of Motazedian and Atkinson (2005) to reproduce the directivity effects, reducing the average error of the spectral amplitudes by 24%. We concluded that although the frequencydependent radiation pattern correction affects the frequency content of the spectral amplitudes simulated, site and directivity effects are more relevant.
    Description: Published
    Description: 662–670
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: reserved
    Keywords: strong motion ; simulation ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
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  • 40
    Publication Date: 2017-04-04
    Description: On October 2002, a seismic swarm occurred on Mt. Etna. One of the strongest events caused severe damage, up to a European Macroseismic Scale intensity of VIII that contrasts with its local magnitude of 4.4. The occurrence of significant damage at such a small magnitude is repeatedly observed in the area and is traditionally attributed to shallow source. Recorded strong-motion accelerograms and broadband seismograms demonstrate that there is one more cause for the severe damage, that is, an anomalously strong low-frequency (0:1 〈 f 〈 1 Hz) radiation deviating from the conventional Brune (1970) spectral scaling. Therefore, these earthquakes cause large ground displacements and long (≈20 sec) durations of shaking. The integration of digital accelerograms yields a maximum peak ground displacement as large as 1.8 cm at a distance of 18 km. Based on the sharp local attenuation of ground motion in the study area, we infer that peak ground displacements near the epicenters did exceed 10 cm. The occurrence of large displacements caused selective damage to medium-rise (≥3 stories) reinforced concrete buildings and elements like church façades. The frequency cutoff below 1.25 Hz in the Wood–Anderson response attenuates the peak-to-peak amplitudes used to assess local magnitudes. Therefore, ML values are not representative of the real strength of volcanic earthquakes. Because a prompt magnitude (and damage potential) assessment is crucial for civil protection actions, a procedure is proposed which, in near-real time, can be successful in identifying potentially damaging earthquakes of Mt. Etna through the computation of pseudovelocity response spectra. The procedure provides a magnitude value that is derived on a statistical basis from the Housner (1952) spectral intensity computed in the low-frequency band. This parameter is a suitable near-real-time indicator of large earthquake-induced building shaking and could also be applied for a preliminary estimate of the epicentral macroseismic intensity.
    Description: Published
    Description: 2724–2738
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: reserved
    Keywords: ground motion estimation ; Long Period volcanic events ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
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  • 41
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    Seismological Society of America
    Publication Date: 2017-04-04
    Description: Since 2005, the Italian Civil Protection (Dipartimento della Protezione Cilvile, DPC) has funded several projects driven toward fast assessment of ground motion shaking in Italy - the final goal being that of organizing the emergency and direct the search and rescue (SAR) teams. To this end, the Istituto Nazionale di Geofisica e Vulcanologia (INGV) has started to determine shakemaps using the USGS-ShakeMap package within 30 minutes from event occurrence and adopting a manually revised location. In this paper we present the INGV implementation of USGS-ShakeMap for earthquakes occurring in Italy and immediately neighboring areas. Emphasis is put on data acquisition, the adopted ground motion predictive relations and the site corrections for the local amplifications of the ground motion. Finally, two examples of shakemaps are shown - the first determined for a recent medium size earthquake, the other for the large Irpinia, 1980, M6.9 event. For both events, the maps are compared to the available macroseismic data.
    Description: Dipartimento Protezione Civile - Italy
    Description: Published
    Description: 689-698
    Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale
    Description: JCR Journal
    Description: open
    Keywords: ground motion estimates ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
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  • 42
    Publication Date: 2017-04-04
    Description: Seismograms from 55 intermediate-depth Vrancea earthquakes (M=4.0- 7.1) recorded at 43 stations of an accelerometric network in Romania are used to derive source spectra and site amplification functions from S-waves in the frequency range 0.5-20 Hz with the generalized inversion technique (GIT) (Castro et al., 1990). Attenuation is taken into account using the nonparametric attenuation functions derived by Oth et al. (2008) from the same dataset, and the attenuation-corrected data are then split into source and site contributions. The source spectra follow the ω-2-model (Brune, 1970, 1971) with high corner frequencies and a related Brune stress drop of the order of 100 MPa. The site amplification functions are determined for both horizontal and vertical components separately. Contrary to wide-spread expectation the vertical component shows significant amplification effects at high frequencies. The H/Z ratios determined from the GIT results compare well with H/V ratios computed directly from the S-wave window of the accelerograms (Lermo and Chávez-García, 1993). The basic assumption for the determination of site effects from H/V ratios is that the vertical component is not or only little affected by site effects. For Vrancea earthquakes, this assumption is incorrect and consequently site effects should not be estimated from H/V ratios. The reason for this peculiar fact is the geometry of intermediate-depth seismicity that leads to almost vertical raypaths beneath the stations.
    Description: In press
    Description: 4.2. TTC - Scenari e mappe di pericolosità sismica
    Description: JCR Journal
    Description: open
    Keywords: Site effect, Source spectra ; Vrancea, Romania ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 43
    Publication Date: 2017-04-04
    Description: The S-wave attenuation characteristics beneath the Vrancea region in Romania are analyzed from the spectra (frequency range 0.5–20 Hz) of more than 850 recordings at 43 accelerometric stations of 55 intermediate-depth earthquakes (M 4:0–7:1) that occurred in the Vrancea seismogenic zone. The method commonly chosen for this type of investigation in the case of crustal earthquakes is the generalized inversion technique (GIT) (e.g., Andrews, 1986; Castro et al., 1990). Yet the Vrancea dataset is entirely different from common crustal datasets. Because of the strong clustering of the hypocenters within a very small focal volume, there are only few crossing ray paths from sources to receivers. As a consequence, inhomogeneities in the attenuation properties are not averaged out, which leads to unphysical results if the standard GIT approach is adopted. The problem is discussed qualitatively by performing tests with synthetic data and solved quantitatively by adapting the GIT technique in view of these peculiarities.With the optimally adapted inversion scheme, it is possible to unravel differences in the attenuation characteristics between two (or more) sets of stations. The results show that the attenuation of seismic waves is roughly comparable in the low frequency range (〈4–5 Hz) but stronger by up to an order of magnitude at higher frequencies within the Carpathian mountain arc as compared with the foreland area. Modeling this strongly frequency-dependent lateral variation of seismic attenuation by a significantly lower Q beneath Vrancea (1) provides a very good fit of observed strong-motion characteristics, (2) sheds new light on the distribution of intensities of the previous strong earthquakes, (3) will have strong implications for future hazard assessment, and (4) is fully compatible with structural models from deep seismic sounding, tomography, and teleseismic attenuation.
    Description: Published
    Description: 2482–2497
    Description: 4.2. TTC - Scenari e mappe di pericolosità sismica
    Description: JCR Journal
    Description: partially_open
    Keywords: S-wave attenuation ground motion spectra ; Vrancea, Romania ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
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  • 44
    Publication Date: 2021-06-21
    Description: Earthquake early warning systems (EEWS), based on real-time prediction of ground motion or structural response measures, may play a role in re- ducing vulnerability and/or exposure of buildings and lifelines. Indeed, seismologists have recently developed efficient methods for real-time es- timation of an event’s magnitude and location based on limited informa- tion of the P-waves. Therefore, when an event occurs, estimates of magni- tude and source-to-site distance are available, and the prediction of the structural demand at the site may be performed by Probabilistic Seismic Hazard Analysis (PSHA) and then by Probabilistic Seismic Demand Analysis (PSDA) depending upon EEWS measures. Such an approach contains a higher level of information with respect to traditional seismic risk analysis and may be used for real-time risk management. However, this kind of prediction is performed in very uncertain conditions which may affect the effectiveness of the system and therefore have to be taken into due account. In the present study the performance of the EWWS under development in the Campania region (southern Italy) is assessed by simu- lation. The earthquake localization is formulated in a Voronoi cells ap- proach, while a Bayesian method is used for magnitude estimation. Simu- lation has an empirical basis but requires no recorded signals. Our results, in terms of hazard analysis and false/missed alarm probabilities, lead us to conclude that the PSHA depending upon the EEWS significantly improves seismic risk prediction at the site and is close to what could be produced if magnitude and distance were deterministically known.
    Description: Published
    Description: 211-232
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: reserved
    Keywords: Earthquake Early ; Campania Region ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion ; 04. Solid Earth::04.06. Seismology::04.06.11. Seismic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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  • 45
    Publication Date: 2020-12-14
    Description: We analyze the dispersion characteristics of ambient noise vibrations. For this purpose, two-dimensional (2D) seismic array data were acquired in four different sites in the Colfiorito plain, an alluvial intramountain basin that exhibits strong site effects. Assuming seismic noise being mainly composed of surface waves, we derive one-dimensional (1D) shallow shear-velocity profiles through the inversion of dispersion curves measured by frequency–wavenumber (f-k) methods. The inverted shear-wave velocity profiles are consistent with a priori information for those sites that can be approximated by 1D simple models. In these cases, the use of passive records of seismic vibrations can be a valuable tool for determining the shallow velocity profile if a detailed depiction of velocity structure is not required. The theoretical dispersion curves for Rayleigh and Love waves were compared with the measured dispersion curves for vertical and horizontal components, respectively. This allows us to discuss qualitatively the composition of ambient vibrations (outlining a large proportion of Love waves in the noise wave field) and the effects of higher modes. We also use the single-station method for investigating the origin of the horizontal-to-vertical (H/V) peak in the plain of Colfiorito in terms of ellipticity of the fundamental Rayleigh mode.
    Description: Published
    Description: 1915-1933
    Description: reserved
    Keywords: surface waves, microtremor, f-k 2D analysis ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 46
    Publication Date: 2017-04-04
    Description: We evaluate the goodness of fit of attenuation relations commonly used for the Italian national territory (Sabetta and Pugliese, 1996) by using the maximum likelihood approaches of Spudich et al. (1999) and Scherbaum et al. (2004). According to the classification scheme proposed by Scherbaum et al. (2004), the Sabetta and Pugliese (1996) relationships show consistent discrepancies between the predicted and the observed peak ground acceleration (PGA) at rock sites in the Umbria- Marche region, central Italy; however, at soft sites the agreement between observations and prediction is satisfactory. The bias of the residuals, computed with the Sabetta and Pugliese (1996) models for PGA, peak ground velocity, (PGV) and pseudovelocity response spectrum (PSV) (for Ml 4–6 and epicentral distances up to 100 km) is negative. This means that on the average, the predictions overestimate the observations, but the overestimation decreases with increasing magnitude. Then, we present regional predictive relations (UMA05) for maximum horizontal PGA, PGV, and 5%-damped PSV, derived from the strong-motion data recorded in the Umbria-Marche area and classified as to four site categories. The UMA05 attenuation relationships for rock sites are log10 (PGA) 2.487 0.534Ml 1.280 log10 (R2 3.942)0.5 0.268 log10 (PGV) 1.803 0.687Ml 1.150 log10 (R2 2.742)0.5 0.300 and log10 (PGA) 2.500 0.544Ml 1.284 log10 Rh 0.292 log10 (PGV) 1.752 0.685Ml 1.167 log10 Rh 0.297, where PGA is measured in fraction of g and PGV in centimeters per second, Ml is the local magnitude in the range 4–6, R is the epicentral distance in the range 1–100 km, and Rh is the hypocentral distance in kilometers. We used the random effect model (Brillinger and Priesler, 1985; Abrahamson and Youngs, 1992; Joyner and Boore, 1993; Joyner and Boore, 1994) to estimate the component of variance related to the earthquake-to-earthquake, station-to-station, and record-to-record variability, and to quantify the benefit of introducing a site classification in the attenuation model to reduce the variance. The introduction of the site classification in the attenuation model allows a reduction of the station-to-station component of variability (from 0.19 to 0.14 for PGA, and from 0.21 to 0.18 for PGV). We also found that the recordto- record component represents the largest contribution to the model uncertainty.
    Description: Published
    Description: 984-1002
    Description: JCR Journal
    Description: reserved
    Keywords: Ground-Motion ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 47
    Publication Date: 2017-04-04
    Description: In order to empirically obtain the scaling relationships for the high-frequency ground motion in the Western Alps (NW Italy), regressions are carried out on more than 7500 seismograms from 957 regional earthquakes. The waveforms were selected from the database of 6 three-component stations of the RSNI (Regional Seismic network of Northwestern Italy). The events,MW ranging between 1.2 and 4.8, were recorded within a hypocentral distance of 200 km during the time period: 1996–2001. The peak ground velocities are measured in selected narrow-frequency bands, between 0.5 and 14 Hz. Results are presented in terms of a regional attenuation function for the vertical ground motion, a set of vertical excitation terms at the reference station STV2 (hard-rock), and a set of site terms (vertical and horizontal), all relative to the vertical component of station STV2. The regional propagation of the ground motion is modeled after quantifying the expected duration of the seismic motion as a function of frequency and hypocentral distance. A simple functional form is used to take into account both the geometrical and the anelastic attenuation: a multi-variable grid search yielded a quality factor Q( f ) = 310 f 0.20, together with a quadri-linear geometrical spreading at low frequency. A simpler, bilinear geometrical spreading seems to be more appropriate at higher frequencies (f 〉 1.0 Hz). Excitation terms are matched by using a Brune spectral model with variable, magnitude-dependent stress drop: at Mw 4.8, we used σ = 50MPa. A regional distanceindependent attenuation parameter is obtained (κ0 = 0.012 s) by modelling the average spectral decay at high frequency of small earthquakes. In order to predict the absolute levels of ground shaking in the region, the excitation/attenuation model is used through the Random Vibration Theory (RVT) with a stochastic point-source model. The expected peak-ground accelerations (PGA) are compared with the ones derived by Ambraseys et al. (1996) for the Mediterranean region and by Sabetta and Pugliese (1996) for the Italian territory.
    Description: Published
    Description: 315-333
    Description: JCR Journal
    Description: reserved
    Keywords: Attenuation ; Ground motion ; Western Alps ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 48
    Publication Date: 2017-04-04
    Description: For early-warning applications in particular, the reliability and efficiency of rapid scenario generation strongly depend on the availability of reliable strong ground-motion prediction tools. If shake maps are used to represent patterns of potential damage as a consequence of large earthquakes, attenuation relations are used as a tool for predicting peak ground-motion parameters and intensities. One of the limitations in the use of attenuation relations is that these have only rarely been retrieved from data collected in the same tectonic environment in which the prediction has to be performed. As a consequence, strong ground motion can result in underestimations or overestimations with respect to the recorded data. This also holds for Italy, and in particular for the Southern Apennines, due to limitations in the available databases, both in terms of distances and magnitude. Moreover, for “real-time” early-warning applications, it is important to have attenuation models for which the parameters can be easily upgraded when new data are collected, whether this has to be done during the earthquake rupture occurrence or in the post-event, when all the strong motion waveforms are available. Here we present a strong-motion attenuation relation for early-warning applications in the Campania region (Southern Apennines), Italy. The model has a classical analytical formulation, and its coefficients were retrieved from a synthetic strong-motion database created by using a stochastic approach. The input parameters for the simulation technique were obtained through the spectral analysis of waveforms of earthquakes recorded by the Istituto Nazionale di Geofisica e Vulcanologia (INGV) network for a magnitude range Md (1.5,5.0) in the last fifteen years, and they have been extrapolated to cover a larger range. To validate the inferred relation, comparisons with two existing attenuation relations are presented. The results show that the calibration of the attenuation parameters, i.e., geometric spreading, quality factor Q, static stress drop values along with their uncertainties, are the main concern.
    Description: Published
    Description: 133-152
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: reserved
    Keywords: A Strong Motion ; Earlywarning ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion ; 04. Solid Earth::04.06. Seismology::04.06.11. Seismic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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  • 49
    Publication Date: 2017-04-04
    Description: In the framework of an ongoing project financed by the Campania Region, a prototype system for seismic early and post-event warning is being developed and tested, based on a dense, wide dynamic seismic network (ISNet) and under installation in the Apennine belt region. This paper reports the characteristics of the seismic network, focussing on the required technological innovation of the different seismic network components (data-logger, sensors and data communication). To ensure a highly dynamic recording range, each station is equipped with two types of sensors: a strong-motion accelerometer and a velocimeter. Data acquisition at the seismic stations is performed using Osiris-6 model data-loggers made by Agecodagis. Each station is supplied with two (120 W) solar panels and two 130 Ah gel cell batteries, ensuring 72-h autonomy for the seismic and radio communication equipment. The site is also equipped with a GSM/GPRS programmable control/alarm system connected to several environmental sensors (door forcing, solar panel controller, battery, fire, etc) and through which the site status is known in real time. The data are stored locally on the hard-disk and, at the same time, continuously transmitted by the SeedLink protocol to local acquisition/analysis nodes (Local Control Center) via Wireless LAN bridge. At each LCC site runs a linux Earthworm system which stores and manages the acquired data stream. The real-time analysis system will perform event detection and localization based on triggers coming from data-loggers and parametric information coming from the other LCCs. Once an event is detected, the system will performs automatic magnitude and focal mechanism estimations. In the immediate post-event period, the RISSC performs shaking map calculations using parameters from the LCCs and/or data from the event database. The recorded earthquake data are stored into an event database, to be available for distribution and visualization for further off-line analyses. The seismic network will be completed in two stages: • Deployment of 30 seismic stations along the southern Apennine chain (to date almost completed) • Setting up a carrier-class radio communication system for fast and reliable data transmission, and installation of 10 additional seismic stations.
    Description: Published
    Description: 325 - 341
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: reserved
    Keywords: Monitoring Infrastructure ; Early-warning Applications ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion ; 04. Solid Earth::04.06. Seismology::04.06.11. Seismic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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  • 50
    Publication Date: 2017-04-04
    Description: The area of Serravalle, sited in the northern part of the town of Vittorio Veneto (TV), NE Italy, has been the target of a seismic microzonation campaign. 10 seismic stations have been deployed for a 7 months period to record in continuous mode. Three stations were installed on bedrock outcrops and seven on sedimentary sites with variable cover thickness. Spectral analyses have been performed on the collected data-set using the Generalized Inversion Technique (GIT, e.g. Andrews, 1986). In particular, spectral ratios have been calculated for each station relatively to the average of the three reference, bedrock sites. The spectral ratios provide quantitative estimates of the seismic motion amplifications which occur in each of the monitored sites. Two sites show high values of amplification, 5 times larger than signal amplitude at the reference sites, in correspondence of well discernible peak frequencies of 5 Hz. Results for the other stations show smaller amounts of site amplification spreading over a broad range of frequencies. Sites where the highest amplifications were recorded all lie on the left bank of the Meschio River and in areas farther away from its outlet into the plain correlating with the presence of thick layers of Quaternary deposits.
    Description: Published
    Description: 31-49
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: reserved
    Keywords: spectral ratios ; reference sites ; site effects ; earthquake grounf motion ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 51
    Publication Date: 2017-04-04
    Description: On 6 September 2002 a Mw 5.9 earthquake occurred in the southern Tyrrhenian sea, 40 km off the coast of Palermo (Italy). In the days after the mainshock, eight temporary stations were installed in the city to record aftershocks on different geological formations. Seismograms of about 30 earthquakes with magnitude 〉 2.8 are analyzed. The data analysis confirms the role of near-surface geology in causing locally significant variations of the ground-shaking level as already inferred by Guidoboni et al. (2003) from historical damage scenario studies. The largest spectral variations estimated through aftershock recordings result in a factor of 10 difference between stiff and soft sites, in frequency bands varying from 1 to 3.5 Hz. The geological structure of the study area is reconstructed by using data from more than 2000 boreholes organized in a Geographic Information System specifically dedicated to the assessment of natural hazards in urban areas. Vertically varying velocity models are used for a comparison with the observed data. In general, 1D transfer functions fit the largest amplification frequency but underestimate amplitudes of observations probably because of 2D and 3D complexity. Because the seismic stations were not installed in free field but at ground or underground level inside buildings, a possible influence of the structure was also investigated. Simultaneous ambient noise measurements were performed on the top, at the base, and outside the buildings where stations were installed. For all but one site, this analysis shows that the estimated ground-motion amplifications do not reflect the building vibration modes and therefore, in these cases, soil–structure interaction does not bias the free-field response of the study sites. Finally, speculations on the effect of the local geology in terms of response spectra of the Mw 5.9 mainshock are discussed in the framework of the Eurocode 8 prescriptions.
    Description: Published
    Description: 2328-2341
    Description: reserved
    Keywords: Palermo, site effects, EC8 ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 52
    Publication Date: 2017-04-04
    Description: Abstract The source parameters of 523 aftershocks (0.5 ML 5.9) of the 1999 Kocaeli earthquake are determined by performing a two-step spectral fitting procedure. The source spectrum, corrected for both site and propagation effects, is described in terms of a standard x-square model multiplied by an exponential term of frequency. The latter term is introduced to estimate the high-frequency (f 12 Hz) fall-off of the acceleration source spectra by computing the j parameter. The seismic moments obtained range between 1.05 1014 and 2.41 1017 N m, whereas the Brune stress drops are between 0.002 and 40 MPa. The j value varies between 0.00 and 0.08 sec, indicating a decay of the acceleration level at the higher frequency part of the spectrum greater than that assumed by the x 2 model. Both the stress drop and the j parameter show the tendency of increasing with aftershock magnitude. No evidence of self-similarity breakdown is observed between the source radius and M0. Finally, both the seismic moment and the moment magnitude are compared with the local magnitude to derive new moment–magnitude relationships for the area.
    Description: Published
    Description: 655-660
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: partially_open
    Keywords: Source parameters ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 53
    Publication Date: 2017-04-04
    Description: By using small-to-moderate-sized earthquakes located within ~200 km of San Francisco, we characterize the scaling of the ground motions for frequencies ranging between 0.25 and 20 Hz, obtaining results for geometric spreading, Q(f), and site parameters using the methods of Mayeda et al. (2005) and Malagnini et al. (2004). The results of the analysis show that, throughout the Bay Area, the average regional attenuation of the ground motion can be modeled with a bilinear geometric spreading function with a 30 km crossover distance, coupled to an anelastic function exp(-pi*f*r/V*Q(f)) , where: Q(f)=180f^0.42. A body-wave geometric spreading, g(r)= r^-1.0, is used at short hypocentral distances (r 〈 30 km), whereas g(r)= r^-0.6 fits the attenuation of the spectral amplitudes at hypocentral distances beyond the crossover. The frequency-dependent site effects at 12 of the Berkeley Digital Seismic Network (BDSN) stations were evaluated in an absolute sense using coda-derived source spectra. Our results show: i) the absolute site response for frequencies ranging between 0.3 Hz and 2.0 Hz correlate with independent estimates of the local magnitude residuals (dML) for each of the stations; ii) moment-magnitudes (MW) derived from our path and site-corrected spectra are in excellent agreement with those independently derived using full-waveform modeling as well as coda-derived source spectra; iii) we use our weak-motion-based relationships to predict motions region wide for the Loma Prieta earthquake, well above the maximum magnitude spanned by our data set, on a completely different set of stations. Results compare well with measurements taken at specific NEHRP site classes; iv) an empirical, magnitude-dependent scaling was necessary for the Brune stress parameter in order to match the large magnitude spectral accelerations and peak ground velocities with our weak-motion-based model.
    Description: Published
    Description: 843-862
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: partially_open
    Keywords: ground motion San Francisco site effects ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 54
    Publication Date: 2017-04-04
    Description: A prototype system for earthquake early warning and rapid shake map evaluation is being developed and tested in southern Italy based on a dense, dynamic seismic network (accelerometers + seismometers) under installation in the Apenninic belt region (Irpinia Seismic Network). It can be classified as a regional Earthquake Early Warning System consisting of a broad-based seismic sensor network covering a portion or the entire area which is threatened by the quake's strike. The real time magnitude estimate will take advantage from the high spatial density of the network in the source region and the broad dynamic range of installed instruments. Based on the offline analysis of high quality strong-motion data bases recorded in Italy, several methods are envisaged, using different observed quantities (peak amplitude, dominant frequency, square velocity integral, …) to be measured on seismograms, as a function of time, both on P and early-S wave signals. Results from the analysis of the Italian strong motion database point out the possibility of using low-pass filtered displacement and velocity peak amplitudes measured in time windows lasting less than 3-4 sec after the first P- or S-wave arrivals. These parameters show they are robustly correlated with moment magnitude. The correlation found of 3Hz low-pass filtered PGV and PGD with magnitude is discussed and interpreted in terms of plausible dynamic models of the earthquake rupture process during its initial stage.
    Description: Published
    Description: 45-63
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: reserved
    Keywords: Real-time Estimation ; Magnitude ; Seismic Early Warning ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion ; 04. Solid Earth::04.06. Seismology::04.06.11. Seismic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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  • 55
    Publication Date: 2017-04-04
    Description: Various authors, analysing the set of accelerograms recorded at Gubbio Piana (GBP) (central Italy), have demonstrated that strong amplification occurs at this accelerometric station, which is installed within an alluvial basin. In particular, Ambraseys et al. [(2005a), Bull Earthq Eng 3:1–53; (2005b), Bull Earth Eng 3:55–73] observed that the strong motion peaks at GBP greatly exceed the median values predicted by the attenuation relationships they derived for Europe. In this work, we analyse and discuss some characteristics of the ground motion recorded at the GBP station. We show that the ground motion parameters, such as peak-ground acceleration and peak-ground velocity, are strongly influenced by the presence of locally induced surface waves that produce both a lengthening of the significant shaking duration and an increase in the peak values with respect to a nearby bedrock site. The basin-induced surface waves are observed in the three components of motion and their effects on the peak values are particularly evident in the vertical component. In the frequency domain, the energy of the surface waves is mostly restricted to the frequency band 0.4–0.8Hz for both the horizontal and vertical components. The horizontal and vertical Fourier amplitudes are also very similar, and this indicates that the H/V spectral ratio technique is not applicable to describing the site response due to the propagation of seismic wave in a complex 2D/3D geological structure. Finally, a preliminary polarization analysis shows that the directions of polarization, as well as the degree of elliptical polarization, exhibit a strong variability with time, that may be related to a complex propagation of Love and Rayleigh waves within the basin.
    Description: Published
    Description: 27-43
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: partially_open
    Keywords: site amplification ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 56
    Publication Date: 2017-04-04
    Description: What can be learned about absolute site effects on ground motions, with no geotechnical information available, in a very poorly instrumented region? In addition, can reliable source spectra be computed at a temporary deployment? These challenges motivated our current study of aftershocks of the 2001 Mw 7.6 Bhuj earthquake, in western India, where we decouple the ambiguity between absolute source radiation and site effects by first computing robust estimates of coda-derived moment-rate spectra of about 200 aftershocks in each of two depth ranges. Crustal attenuation and spreading relationships, based on the same data used here, were determined in an an earlier study. Using our new estimates of source spectra, and our understanding of regional wave propagation, for direct S waves we isolate the absolute site terms for the stations of the temporary deployment. Absolute site terms for each station were determined in an average sense for the three components of the ground motion via an L1-norm minimization. Results for each site were averaged over wide ranges of azimuths and incidence angles. The Bhuj deployment is characterized by a variable shallow geology, mostly of soft sedimentary units. Vertical site terms in the region were observed to be almost featureless (i.e., flat), with amplifications slightly 1.0 within wide frequency ranges. As a result, the horizontal-to-vertical (H/V) spectral ratios observed at the deployment mimic the behavior of the corresponding absolute horizontal site terms, and they generally overpredict them. This differs significantly from results for sedimentary rock sites (limestone, dolomite) obtained by Malagnini et al. (2004) in northeastern Italy, where the H/V spectral ratios had little in common with the absolute horizontal site terms. Spectral ratios between the vector sum of the computed horizontal site terms for the temporary deployment with respect to the same quantity computed at the hardest rock station available, BAC1, are seriously biased by its nonflat, nonunitary site response. This indicates that, occasionally, the actual behavior of a rock outcrop may be far from that of an ideal, reference site (Steidl et al., 1996).
    Description: Published
    Description: 456-466
    Description: JCR Journal
    Description: reserved
    Keywords: Aftershocks ; Bhuj Earthquake ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 57
    Publication Date: 2017-04-04
    Description: Paleoseismic evidence and seismic-hazard analysis suggest that the city of Rome, Italy, has experienced considerable earthquake ground motion since its establishment more than 2000 years ago. Seismic hazards in Rome are mainly associated with two active seismogenic areas: the Alban Hills and the Central Apennines regions, located about 20 km southeast and 80–100 km east of central Rome. Within the twentieth century, M 6.8 and M 5.3 earthquakes in the Apennines and the Alban Hills, respectively, have generated intensities up to Mercalli-Cancani-Sieberg scale (MCS) VII in the city. With a lack of strong-motion records, we have generated a 3D velocity model for Rome, embedded in a 1D regional model, and estimated long-period ( 1 Hz) ground motions for such scenarios from finite-difference simulations of viscoelastic wave propagation. We find 1-Hz peak ground velocities (PGVs) and peak ground accelerations (PGAs) of up to 14 cm/sec and 44 cm/sec2, respectively, for a M 5.3 Alban Hills scenario, largest near the northwestern edge of the Tiber River. Our six simulations of a M 7.0 Central Apennine scenario generate 0.5-Hz PGVs in Rome of up to 9 cm/sec, as well as extended duration up to 60 sec. The peak motions are similar to, but the durations much longer than those from previous studies that omitted important wave-guide effects between the source and the city. The results from the two scenarios show that the strongest ground-motion amplification in Rome occurs in the Holocene alluvial areas, with strong basin edge effects in the Tiber River valley. Our results are in agreement with earlier 2D SHwave results showing amplification of peak velocities by up to a factor of 2 in the alluvial sediments, largest near the contact to the surrounding Plio-Pleistocene formations. Our results suggest that both earthquakes from the Alban Hills and the Central Apennines regions contribute to the seismic hazards in Rome. Although earthquakes from the former area may generate the larger peak motions, seismic waves from the latter region may generate ground motions with extended durations capable of causing significant damage on the built environment.
    Description: Published
    Description: 133-146
    Description: JCR Journal
    Description: reserved
    Keywords: Ground-Motion ; 3-D ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 58
    Publication Date: 2017-04-03
    Description: The U.S. Geological Survey deployed a digital seismic station in Oceano, California, in February 2004, to investigate the cause of damage and liquefaction from the 22 December 2003 Mw 6.5 San Simeon earthquake. This station recorded 11 Mw 2.8 aftershocks in almost 8 weeks. We analyze these recordings, together with recordings of the mainshock and the same aftershocks obtained from nearby stations in Park Hill and San Luis Obispo, to estimate the mainshock ground motion in Oceano. We estimate the Fourier amplitude spectrum using generalized spectral ratio analysis. We test a set of aftershocks as Green’s functions by comparing simulated and recorded acceleration amplitude spectra for the mainshock at San Luis Obispo and Park Hill. We convolve the aftershock accelerograms with a stochastic operator to simulate the duration and phase of the mainshock accelerograms. This approximation allows us to extend the range of aftershocks that can be used as Green’s functions to events nearly three magnitude units smaller than the mainshock. Our realizations for the mainshock accelerogram at Oceano yield peak ground accelerations distributed as 28% +/- 4%g. We interpret these realizations as upper bounds for the actual ground motion, because our analysis assumes a linear response, whereas the presence of liquefaction indicates that the ground behaved nonlinearly in Oceano.
    Description: U.S.G.S University of Naples “Federico II” University of Rome “La Sapienza,”
    Description: Published
    Description: 1437–1447
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: reserved
    Keywords: Stochastic, ; simulation, ; ground motion, ; spectral ratio ; Green’s function ; earthquake ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 59
    Publication Date: 2022-05-24
    Description: Various authors, analysing the set of accelerograms recorded at Gubbio Piana (GBP) (central Italy), have demonstrated that strong amplification occurs at this accelerometric station, which is installed within an alluvial basin. In particular, Ambraseys et al. [(2005a), Bull Earthq Eng 3:1–53; (2005b), Bull Earth Eng 3:55–73] observed that the strong motion peaks at GBP greatly exceed the median values predicted by the attenuation relationships they derived for Europe. In this work, we analyse and discuss some characteristics of the ground motion recorded at the GBP station. We show that the ground motion parameters, such as peak-ground acceleration and peak-ground velocity, are strongly influenced by the presence of locally induced surface waves that produce both a lengthening of the significant shaking duration and an increase in the peak values with respect to a nearby bedrock site. The basin-induced surface waves are observed in the three components of motion and their effects on the peak values are particularly evident in the vertical component. In the frequency domain, the energy of the surface waves is mostly restricted to the frequency band 0.4–0.8Hz for both the horizontal and vertical components. The horizontal and vertical Fourier amplitudes are also very similar, and this indicates that the H/V spectral ratio technique is not applicable to describing the site response due to the propagation of seismic wave in a complex 2D/3D geological structure. Finally, a preliminary polarization analysis shows that the directions of polarization, as well as the degree of elliptical polarization, exhibit a strong variability with time, that may be related to a complex propagation of Love and Rayleigh waves within the basin.
    Description: Published
    Description: JCR Journal
    Description: reserved
    Keywords: Strong motion ; Alluvial basin effects ; Site effects ; Gubbio plain ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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