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  • 1
    Publication Date: 2021-04-20
    Description: Alle ore 02.03 UTC di domenica 20 maggio 2012, la Rete Sismica Nazionale (RSN [Amato and Mele, 2008; Delladio, 2011]) dell’Istituto Nazionale di Geofisica e Vulcanologia (INGV) ha registrato un evento simico di magnitudo locale 5.9 che è stato avvertito in gran parte dell’Italia centro-settentrionale; l’evento è stato localizzato sotto la valle del Po in Emilia (44.89° N, 11.23° E e 6.3 km di profondità). Subito dopo la scossa principale, è stato attivato il Pronto Intervento Sismico dell’INGV al fine di installare una rete sismica temporanea ad integrazione delle stazioni permanenti già presenti in area epicentrale. Grazie alla collaborazione fra le sedi INGV di Ancona, Arezzo, Bologna, Irpinia (Grottaminarda), Milano, Pisa e Roma sono state installate 44 stazioni temporanee, di cui 10 in trasmissione real-time con la sala di sorveglianza simica della sede di Roma. Contemporaneamente altre 38 stazioni sismiche temporanee sono state inoltre installate dal Dipartimento della Protezione Civile – DPC (16 stazioni strong motion), dall’Istituto Nazionale di Oceanografia e di Geofisica Sperimentale – OGS (8 stazioni stand-alone) e da enti francesi (14 stazioni stand-alone). In una seconda fase, l’8 giugno 2012, è stato attivato anche il Centro Operativo Emergenza Sismica (COES [Moretti et al., 2010a]), all’interno della Direzione di Comando e Controllo (Di.Coma.C.) del DPC predisposto presso l’Agenzia della Protezione Civile Regionale dell’Emilia Romagna (Bologna). L’allestimento e il coordinamento della struttura sono stati realizzati grazie alla collaborazione tra il Centro Nazionale Terremoti (CNT) e la Sezione di Bologna. Il COES ha garantito la comunicazione costante e diretta con i funzionari DPC presenti nell'area epicentrale. Allo stesso tempo, la struttura è stata proposta come supporto logistico per tutti i colleghi dell’INGV impegnati in attività nella zona epicentrale (reti sismiche Mobili, EMERSITO, GPS, EMERGEO, QUEST) e per sostenere il servizio dedicato alla “Comunicazione e Informazione” promosso a favore delle popolazioni colpite, degli operatori della protezione civile e dei volontari di soccorso. In questo lavoro saranno descritte le attività svolte nel primo mese di emergenza, le modalità e le tempistiche dell’intervento, le strutture coinvolte.
    Description: Published
    Description: 1-43
    Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale
    Description: N/A or not JCR
    Description: open
    Keywords: Emilia 2012 sequence ; Seismic networks ; Seismological data ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
    Publication Date: 2020-12-14
    Description: The objective of this work is to perform a purely empirical assessment of the actual capabilities of the horizontal-to-vertical (H/V) spectral ratio technique to provide reliable and relevant information concerning site conditions and/or site amplification. This objective has been tackled through the homogeneous (re)processing of a large volume of earthquakes and ambient noise data recorded by different research teams in more than 200 sites located mainly in Europe, but also in the Caribbean and in Tehran. The original recordings were first gathered in a specific database with information on both the sites and recorded events. Then, for all sites close to an instrumented reference, average site-to-reference spectral ratios (“spectral ratio method” (SSR)) were derived in a homogeneous way (window selection, smoothing, signal-to-noise ratio threshold, averaging), as well as H/V ratios (“HVSRE–RF”) on earthquake recordings. H/V ratios were also obtained from noise recordings at each site (either specific measurements, or extracted from pre- or post-event noise windows). The spectral curves resulting from these three techniques were estimated reliable for a subset of 104 sites, and were thus compared in terms of fundamental frequency, amplitude and amplification bandwidth, exhibiting agreements and disagreements, for which interpretations are looked for in relation with characteristics of site conditions. The first important result consists in the very good agreement between fundamental frequencies obtained with either technique, observed for 81% of the analyzed sites. A significant part of the disagreements correspond to thick, low frequency, continental sites where natural noise level is often very low and H/V noise ratios do not exhibit any clear peak. The second important result is the absence of correlation between H/V peak amplitude and the actual site amplification measured on site-to-reference spectral ratios. There are, however, two statistically significant results about the amplitude of the H/V curve: the peak amplitude may be considered as a lower bound estimate of the actual amplification indicated by SSR (it is smaller for 79% of the 104 investigated sites), and, from another point of view, the difference in amplitude exhibits a questioning correlation with the geometrical characteristics of the sediment/basement interface: large SSR/HV differences might thus help to detect the existence of significant 2D or 3D effects.
    Description: Published
    Description: 75-108
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: reserved
    Keywords: Microtremor ; H/V ; Site effects ; SESAME ; 04. Solid Earth::04.02. Exploration geophysics::04.02.06. Seismic methods ; 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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  • 3
    Publication Date: 2017-04-04
    Description: The city of Palermo (southern Italy) was severely damaged in the past by moderate-magnitude earthquakes located tens of kilometres offshore. The historical monumental heritage and the high density of population motivated large efforts for the seismic risk assessment. We present the geological and seismological studies performed in downtown Palermo as a study case to show how the complexity of an urban environment can be approached with multidisciplinary investigations. Downtown Palermo is characterized by sea deposits in the coastal zone and the alluvial deposits of two rivers (Papireto and Kemonia) of about 150 m width, which were buried and filled during the XVII century. The difficulty of surface geological surveys was compensated through an analysis of aerial photos and more than 2000 borehole data organized in the City-GIS of the Department of Geology and Geodesy of the University of Palermo. A previous study on the well-documented historical damage indicated the major role played by the two river valleys and the sea deposits in controlling the damage distribution, above the assumption of a fairly homogeneous vulnerability of the existing buildings in downtown. To test the feasibility of using ambient noise for recognizing the presence of alluvial deposits in a densely urbanized environment, a large microtremor measurement campaign was performed in Palermo across several profiles. The frequency peaks inferred from the horizontal-to-vertical spectral ratio were compared with numerical simulations to assess the seismic velocity profile and the soil stratigraphy. Moreover, noise data were analyzed through a statistical approach to establish a possible correlation between damage, resonance frequency and amplitude, and geology. After the moderate earthquake of September 6, 2002 (Mw=5.9, 50 km far away), the analysis of the aftershock sequence provided a well documented estimate of the variation of ground motion within the city in the case of linear soil response. Using these aftershocks we computed also synthetic accelerograms of the main shock through Empirical Green’s Functions that provided ground accelerations as large as 50 gals, consistently with the documented EMS-98 intensity. Synthetic accelerograms showed a large variability of horizontal ground motion within the city (a factor of 3 – 4) that confirms the role of local geology in causing an increase of the seismic hazard on sea and alluvial deposits. Finally, we discuss the comparison between the acceleration response spectra calculated for different soil categories and the design elastic spectra provided by EC8.
    Description: Unpublished
    Description: Lisbon, Portugal
    Description: open
    Keywords: microtremors ; numerical simulations ; earthquake recordings ; 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::04.06.11. Seismic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Poster session
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  • 4
    Publication Date: 2017-04-04
    Description: This study presents the results of 90 seismic ambient noise measurements in Palermo, the main city of Sicily (Italy). The dataset has been processed using the horizontal-to-vertical spectral ratio (HVNSR) technique and interpreted in terms of local geology, which is characterized by the presence of alluvial sediments of two river-beds masked by urbanization since the 17th century. HVNSRs show significant variations in the study area: when the transition stiff-to-soft is crossed, a typical spectral peak appears in the HVNSRs, mostly in the frequency band 1 to 2 Hz, and exceeding a factor of 3 in amplitude. Using available information on sub-surface geological structure we compute theoretical 1- and 2-D transfer functions. The resonance frequencies of soft soils obtained by HVNSR are well reproduced by the fundamental frequencies from numerical modeling. The distribution of frequency peaks of HVNSR and their amplitudes are also compared with the local damage caused by historical earthquakes. Previous studies demonstrated that damage variations in Palermo were controlled more by near-surface geology than building vulnerability. A uniform vulnerability is an ideal condition to test statistical methods and their capability in seeking correlation between HVNSR and potential damage due to local geological conditions. We apply two well-established multivariate statistical methodologies (factor analysis and canonical correlation) to the HVNSR dataset and macroseismic data (damage grades of the European Macroseismic Scale). Through these analyses we quantify the significance of the correlation between the HVNSR peak in the low-medium frequency range (0.5-3 Hz) and the occurrence of the highest damage grades. This approach allows us i) to estimate the threshold value in the resulting linear combination of the HVNSR amplitudes which separates zones of light damage from zones of significant damage, and therefore ii) to improve the spatial definition of potentially high hazard zones through a denser grid of microtremor measurements.
    Description: In press
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: open
    Keywords: microtremor ; site effects ; statistical analyses ; 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
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: manuscript
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  • 5
    Publication Date: 2017-04-04
    Description: The Horizontal-to-Vertical Spectral Ratio from earthquake recordings (HVSR) and from ambient noise recordings (HVN) realistically indicate fundamental frequency but, for the majority of the worldwide examined sites, they do not provide reliable amplification curves as predicted by the earthquake Spectral Ratio to a reference site (SSR). Given the fact that HVSR and especially HVN can be easily obtained, it is challenging to search for a meaningful correlation with SSR amplification functions in the whole frequency band. To this aim we used recordings from 75 sites worldwide and we applied a multivariate statistical approach (the canonical correlation analysis) to investigate and quantify any correlation among spectral ratios and, from a subset of sites in sedimentary basins, with geometrical and geophysical parameters (S-wave velocity and the 2D geometry of the valley). Results show a correlation between SSR and HVN or HVSR that can be statistically quantified, and it is modulated in specific frequency range. Moreover, the larger are the Vs30, the bedrock depth and the valley’s shape ratio, the higher is the low-frequency amplitude in HVSR and HVN, and the lower is the high-frequency value. Despite the limitation of the database, the correlation results can be used to estimate the excepted SSR spectral ratio of specific sites in the investigated areas when only noise measurements are available(see the companion paper De Rubeis et al., 2012).
    Description: Submitted
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: reserved
    Keywords: Statistical seismology ; Earthquake ground motions ; Site effects ; Basin effects ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: manuscript
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  • 6
    Publication Date: 2017-04-03
    Description: The idea of this Special Issue comes from a “joint venture” of research groups from several Italian and European Institutions (Istituto Nazionale di Geofisica e Vulcanolo- gia and University of Basilicata, Italy; GeoForschungsZentrum-GFZ, Germany; CETE Méditerranée—LRPC Nice and OCA-UMR Géoazur, France) which carried out a large seismic survey for site effect estimation in the wide area hit by the 2009 L’Aquila, Italy, earthquake (Fig. 1). The Mw 6.3 mainshock of April 6th, 2009, represented the most damaging event in Italy since the 1980 Irpinia earthquake (Mw 6.9). Several large aftershocks (Mw 〉 5) and thousands of smaller events occurred in the following months and the deployment of differ- ent rapid response seismic networks from Italy, France and Germany allowed the scientific community to collect a very large and high quality data set, probably the largest ever acquired during a normal fault seismic sequence (Marzorati et al. 2011).
    Description: Published
    Description: 691-695
    Description: JCR Journal
    Description: restricted
    Keywords: Aquila Earthquakes of April 2009 ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 7
    Publication Date: 2017-04-04
    Description: The Horizontal-to-Vertical Spectral Ratio from earthquake (HVSR) and from ambient noise (HVN) recordings realistically indicate the fundamental frequency of soil response but, for the majority of the worldwide examined sites, they do not provide reliable amplification curves as calculated by the earthquake standard Spectral Ratio (SSR). Given the fact that HVSR and especially HVN can be easily obtained, it is challenging to search for a meaningful correlation with SSR amplification functions for the entire frequency band and to use the results for the SSR estimate at a further site where only noise measurements are available. To this aim we used recordings from 75 sites worldwide and we applied a multivariate statistical approach (canonical correlation analysis) to investigate and quantify any correlation among spectral ratios. The canonical correlation between SSR and HVN is then used to estimate the expected SSR at each site by a weighted average of the SSR values measured at the other sites; the weights are properly set to account more for sites with similar behaviour in terms of the canonical correlation results between HVN and SSR. This procedure, repeated for all sites in turn, constitutes the basis of a cross validation. The comparison between the inferred and the original SSR highlights the improvements of site response estimation with respect to the use of ambient noise techniques. The goodness and limitations of the reconstruction procedure are explained by specific geological settings.
    Description: Published
    Description: 1493-1514
    Description: 3T. Pericolosità sismica e contributo alla definizione del rischio
    Description: JCR Journal
    Description: restricted
    Keywords: Earthquake ground motions ; Ambient noise ; Site effects ; Statistical seismology ; 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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  • 8
    Publication Date: 2017-04-04
    Description: The May 20, 2012, Emilia Ml 5.9 earthquake was followed by some major aftershocks, well recorded by a large number of temporary stations that were installed to monitor the sequence. These additional recordings allowed us a thorough testing of the performance of the ShakeMap—a procedure designed to provide rapid information on the experienced ground motion. We found that the shakemaps for the May 29, 2012, Ml 5.8 earthquake, obtained using the permanent stations only, underestimate significantly the ground motion computed with the highest station density, especially for PSA at long periods (T=3.0 s). This low-frequency motion is controlled primarily by the surface waves recorded in the Po plain: the observed site effects are likely not accounted properly by the site correction coefficient based on Vs30 as implemented in the ShakeMap procedure. The shakemaps determined during the seismic sequence have been included in an Italian national law that was passed after the 2012 earthquake. According to this law, the factories safety verifications were bound to the comparison between the shakemaps and the design acceleration required by the current national seismic code.We then decide to appraise the impact of the shakemap accuracy on the law provisions. Following the law ecommendations, we have estimated the possible errors resulting from the incomplete evaluation of the ground shaking: our results show that, if the complete dataset were available at the time of the law approval, the number of buildings for which the safety check was required would have been significantly smaller.
    Description: Published
    Description: 2147-2164
    Description: 3T. Pericolosità sismica e contributo alla definizione del rischio
    Description: 5T. Sorveglianza sismica e operatività post-terremoto
    Description: JCR Journal
    Description: restricted
    Keywords: Emilia earthquake ; Shakemap ; Strong ground motion ; Seismic hazard ; 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::04.06.11. Seismic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 9
    Publication Date: 2019-11-04
    Description: A site response experiment was performed in the basin of Città di Castello (a small town in Central Italy) in May 2001. This study is part of a project on the evaluation of seismic hazard in seismogenic areas funded by the Gruppo Nazionale Difesa dai Terremoti (GNDT). The experiment consisted of a dense fixed transect configuration with most of the stations recording in continuous mode, and several ambient noise measurements both in single station and in array configuration spread over the investigated area. The dense transect was composed of 26 seismic stations in a crosswise configuration with a maximum inter-station distance of 250 m. The stations were deployed in the southern part of the basin, from the eastern bedrock outcrop to the western edge, across the town. About 70 earthquakes were recorded during 10 days of deployment, generally low magnitude or regional events. We located 23 earthquakes and 17 of them were located using the waveform similarity approach at 4 stations outside the target area. These 4 stations were part of a dense temporary seismic network involved in a previous experiment of the same project, aimed at performing a high-resolution picture of the local seismicity. Delay analysis on the recorded waveforms allowed us to infer the basin geometry at depth and estimate the S-wave velocity of sediments. Moreover, we evaluated relative site response along the E-W transect by performing a standard spectral ratio. Amplification factors up to 9 are found inside the basin; at frequencies above 5 Hz stations closer to the edges show higher amplification, whereas stations located in the middle of the basin, where the alluvial sediments are thicker (CD11-CD14), show higher amplification below 5 Hz. We considered the average amplification in two frequency bands (1-5 Hz and 5-10 Hz), representative of the resonance frequency for 2-3 storey buildings and 1 storey houses,respectively. Our results suggest that the potential hazard for 2-3 storey buildings is higher in the center of the basin (amplification factor up to 6), and for 1 storey houses is higher at the edges (amplification factor up to 5).
    Description: Published
    Description: JCR Journal
    Description: open
    Keywords: dense seismic array ; weak motion ; ambient noise ; basin geometry ; urban area ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring ; 04. Solid Earth::04.06. Seismology::04.06.10. Instruments and techniques
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 10
    Publication Date: 2022-04-22
    Description: No abstract
    Description: Published
    Description: 583-590
    Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale
    Description: JCR Journal
    Description: open
    Keywords: Seismological data ; Emilia 2012 sequence ; 04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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