Database of Individual Seismogenic Sources (DISS), Version 3.2.1: A compilation of potential sources for earthquakes larger than M 5.5 in Italy and surrounding areas

Istituto Nazionale di Geofisica e VulcanologiaPublished2T. Deformazione crostale attiva3T. Sorgente sismica4T. Sismicità dell'Italia5T. Sismologia, geofisica e geologia per l'ingegneria sismica6T. Studi di pericolosità sismica e da maremoto4IT. Banche dat

Surface ruptures database related to the 26 December 2018, MW 4.9 Mt. Etna earthquake, southern Italy

We provide a database of the surface ruptures produced by the 26 December 2018 Mw 4.9 earthquake that struck the eastern flank of Mt. Etna volcano in Sicily (southern Italy). Despite its relatively small magnitude, this shallow earthquake caused about 8 km of surface faulting, along the trace of the NNW-trending active Fiandaca Fault. Detailed field surveys have been performed in the epicentral area to map the ruptures and to characterize their kinematics. The surface ruptures show a dominant right-oblique sense of displacement with an average slip of about 0.09 m and a maximum value of 0.35 m. We have parsed and organized all observations in a concise database, with 932 homogeneous georeferenced records. The Fiandaca Fault is part of the complex active Timpe faults system affecting the eastern flank of Etna, and its seismic history indicates a prominent surface-faulting potential. Therefore, this database is essential for unravelling the seismotectonics of shallow earthquakes in volcanic areas, and contributes updating empirical scaling regressions that relate magnitude and extent of surface faulting.Publishedid 422T. Deformazione crostale attivaJCR Journa

Site effect studies following the 2016 Mw 6.0 Amatrice Earthquake (Italy): the Emersito Task Force activities

On August 24, 2016, at 01:36 UTC a MW 6.0 earthquake struck an extensive area of the Central Apennines (Italy) be-tween the towns of Norcia and Amatrice. Due to the mainshock magnitude and the widespread damaging level of build-ings in the epicentral area, the Emersito task force has been mobilized by the Istituto Nazionale di Geofisica e Vulcanologia (INGV). The aim of Emersito is to carry out and coordinate the monitoring of local site effects, caused by geological and geomorphological settings. During the first days of the seismic emergency, Emersito installed a tempo-rary seismic network for site effect studies at 4 municipalities close to the epicentral area (Amandola, Civitella del Tronto, Montereale and Capitignano), using 22 stations equipped with both velocimetric and accelerometric sensors. The selection of the sites where stations have been installed was mainly driven by the proximity to the epicentral area (without interfere with the rescue operations) and by peculiar geologic and geomorphologic settings (topographic irregu-larities, fault zones, alluvial plains). Preliminary analyses performed on ambient noise and aftershocks signals show that directional amplification effects may have occurred at stations installed on the top of topographic irregularities. We also observed the lengthening and amplification of the seismograms and a variability of the peaked frequency across the sedi-mentary basin between Montereale and Capitignano, probably related to a different thickness of the deposits. Further analyses are necessary to assess the correlation with surface geology.Published4T. Sismologia, geofisica e geologia per l'ingegneria sismica1SR. TERREMOTI - Servizi e ricerca per la Società1IT. Reti di monitoraggioJCR Journa

Surface ruptures following the 26 December 2018, Mw 4.9, Mt. Etna earthquake, Sicily (Italy)

We present a 1:10,000 scale map of the coseismic surface ruptures following the 26 December 2018 Mw 4.9 earthquake that struck the eastern flank of Mt. Etna volcano (southern Italy). Detailed rupture mapping is based on extensive field surveys in the epicentral region. Despite the small size of the event, we were able to document surface faulting for about 8 km along the trace of the NNW-trending active Fiandaca Fault, belonging to the Timpe tectonic system in the eastern flank of the volcano. The mapped ruptures are characterized in most cases by perceivable opening and by a dominant right-oblique sense of slip, with an average slip of about 0.09 m and a peak value of 0.35 m. It is also noteworthy that the ruptures vary significantly in their kinematic expression, denoting locally high degree of complexity of the surface faulting.Published831-8372T. Deformazione crostale attivaJCR Journa

Il terremoto di Fleri (Etna) del 26 dicembre 2018 Mw 4.9. Parte II: rilievo degli effetti di fagliazione cosismica superficiale

Il terremoto del 26 dicembre 2019, ore 02:19 UTC, che ha colpito il basso versante sud-orientale dell’Etna, ha prodotto non solo danni gravi e distruzioni nell’area epicentrale, pari al grado 8 EMS (Azzaro et al., in questo volume), ma anche vistose rotture superficiali lungo la faglia di Fiandaca, che è la struttura più meridionale del sistema tettonico delle Timpe (Fig. 1a). Gli effetti di fagliazione cosismica in area etnea sono storicamente piuttosto frequenti in occasione di terremoti superficiali (< 2-3 km), anche per valori di magnitudo relativamente modesti (M ≥ 3.5, vedi Azzaro, 1999). Con una magnitudo Mw 4.9 (Regional Centroid Moment Tensors, https://doi.org/10.13127/rcmt/italy), il terremoto in questione rappresenta l’evento più significativo, in termini di entità e complessità della fagliazione associata, verificatosi nell’area etnea negli ultimi 70 anni, con una estensione della rottura superiore rispetto a quelle storiche (< 6.5 km). Il gruppo di emergenza per il rilievo degli effetti geologici cosismici EMERGEO (http://emergeo.ingv.it) dell’INGV, si è pertanto attivato effettuando quattro campagne di misura con squadre che si sono alternate sul terreno (per un totale di 60 gg/persona), supportate da personale del proprio Centro Operativo per l’organizzazione dei dati e il popolamento del database (43 gg/persona). Il rilievo ha consentito la raccolta e catalogazione di circa 900 punti di misura relativi a posizionamento, geometria, rigetto e cinematica delle fratture cosismiche.UnpublishedRoma2T. Deformazione crostale attiv

Gruppo Operativo Emersito++ Evento Sismico Ischia 2017: Campagne Di Misure Geofisiche, Rapporto N°1

Rapporto Tecnico n°1 della task force operativa EMERSITO++ (INGV) che descrive le campagne sismiche ed elettromagnetiche condotte nei comuni di Casamicciola Terme e di Lacco Ameno a seguito del terremoto di Ischia del 21 Agosto 2017.INGVPublished4T. Sismologia, geofisica e geologia per l'ingegneria sismica1SR. TERREMOTI - Servizi e ricerca per la SocietàN/A or not JC

L'uso delle misure di microtremore per investigare le strutture tettoniche sepolte: il caso di studio dell'anticlinale di Mirandola

L'anticlinale di Mirandola rappresenta una piega per propagazione di faglia sepolta che si è accresciuta nel Quaternario a seguito della attività sismogenica di un segmento cieco dell'Arco Ferrarese. L'ultima riattivazione si è verificata durante la sequenza sismica dell'Emilia del maggio 2012. In corrispondenza di tale struttura lo spessore dei depositi marini e continentali della avanfossa padana è particolarmente ridotto. Al fine di meglio definire la geometria superficiale di questa struttura tettonica, e quindi la sua recente attività, è stato studiato un intervallo di profondità, che è intermedio tra le osservazioni morfologiche superficiali e le informazioni ricavate dai profili sismici. In particolare, sono state effettuate numerose misure di sismica passiva (microtremori a stazione singola) per ottenere il rapporto spettrale tra le componenti orizzontali e quella verticale (HVSR). I risultati di un'analisi combinata della frequenza di picco e della sua ampiezza ben si accordano alle informazioni geologiche disponibili suggerendo che questa tecnica geofisica a basso costo può essere applicata con successo in altri settori di ampie piane alluvionali morfologicamente piatte per investigare potenziali strutture sismogeniche cieche e completamente sepolte.The Mirandola Anticline represents a buried fault-propagation fold which has been growing during Quaternary due to the seismogenic activity of a blind segment belonging to the broader Ferrara Arc. The last reactivation occurred during the May 2012 Emilia sequence. In correspondence with this structure the thickness of the marine and continental deposits of the Po Plain foredeep is particularly reduced. In order to better define the shallow geometry of this tectonic structure, and hence its recent activity, a depth range which is intermediate between the surficial morphological observations and seismic profiles information was investigated. In particular, numerous passive seismic measurements (single station microtremor) for obtaining the horizontal to vertical spectral ratio (HVSR) were carried out. For each site the amplitude of the peak value of the HVSR curve, A, and the corresponding frequency, f0 (commonly referred to as natural frequency), have been considered. The distribution of both parameters has been further elaborated by creating a colour-shaded map. The results of the geophysical campaign and the gridding clearly document the presence of areas characterized by resonance phenomena, locally very important ones, and allow to map their distribution. In particular a first map evidences the occurrence of a narrow zone (2.5-3.5 km-wide), trending ESE-WNW and characterized by A values of the HVSR curves greater than 2.5. Local maxima occur, from west to east, along the central sector. A similar pattern could be also observed in a second map, where the natural frequency f0 has been interpolated with the same procedure described above. In this case, the selected discriminant value is ca. 1 Hz and the gridding emphasizes an elongated ESE-WNW trending area characterized by natural frequencies up to 2.0 Hz. Assuming as a first approximation laterally uniform (or smoothly variable) seismic waves velocities within the uppermost sedimentary units, say the first 100150 m, the mapped distribution of the natural frequencies is certainly due to a strongly variable depth of the surface producing the resonance (i.e. characterized by an impedance contrast). The areas emphasized in the two maps basically coincide and are both characterized by marked gradients north and south and a progressive fading ESE-wards. Position and dimensions of the overlapping area as well as the corresponding values of the two mapped parameters are due to laterally changing impedance contrast associated with the variable stratigraphic succession developed during Pliocene-Quaternary on top of the Mirandola anticline. In order to further constrain and validate the subsoil model here proposed, HVSR measurements were also carried out in correspondence of two boreholes cored by Regione Emilia-Romagna down to a depth of 101 and 127 m, respectively. Accordingly, at these two sites the detailed stratigraphic succession has been reconstructed showing the occurrence of the Pliocene top, the so called seismic pseudo-bedrock interface of the area (i.e. vs ≥ 600 m/s) at ca. 96 and 113 m, respectively. Moreover, at both sites a second borehole was drilled to perform a crosshole investigation for measuring the velocity distribution at depth. Based on a simplified inversion approach I succeeded to reproduce measured HVSR curves and particularly the major and meaningful peaks down to the bedrock interface separating the continental Middle Quaternary from the marine Early Quaternary-Late Pliocene deposits. The results of a combined analysis of the peak frequency and its amplitude nicely fit also the available geological information derived from boreholes and seismic reflection profiles carried out for hydrocarbon purposes, suggesting that this low-cost geophysical technique could be successfully applied in other sectors of wide morphologically flat alluvial plains to investigate blind and completely buried potential seismogenic structures. One of the major results of the present reasearch consists in the reconstruction of the natural amplification distribution associated with, and caused by, the presence of impedance contrast in the subsoil. As above mentioned, this information has been obtained either in terms of frequency and amplitude of the HVSR. This study also shows how the systematic application of the HVSR method, a low-cost non-invasive geophysical technique, generating a relatively dense grid of measurements over a wide area and strictly following as a standard the well tested SESAME criteria, could allow to laterally correlate specific amplification peaks and hence to interpolate with confidence the same impedance contrast surface. According to the instrumentation used and the stratigraphic setting of the investigated area, such a surface that represents the real target of the whole procedure could be up to 150-200 m-deep. The capacity to model it in some detail could enable to map large-scale deformations, which are too subtle to be reconstructed on the basis of morphological analyses (due to the lack of cumulative effects) and generally too shallow to be taken into account during seismic reflection surveys devoted to hydrocarbon exploration. Finally, the application of the above procedure to the Mirandola case study allowed to emphasize the persisting and recent growth of a major fault-propagation anticline, where both the causative thrust and the associated fold are completely buried by the Middle-Upper Pleistocene to Holocene continental deposits (e.g. Martelli and Molinari 2008; Bonini et al. 2014). At this regard, the obtained results clearly and independently document the presence of a folded surface in the shallow Mirandola subsoil; the crest is oriented ESE-WNW with a culmination towards the west and a periclinal setting eastwards in perfect agreement with the deeper tectonic structure reconstructed on the basis of seismic reflection profiles. The results of this methodological approach are quite encouraging and could be easily applied to other morphologically flat regions affected by blind faulting and folding. Seismic amplification is influenced by the stiffness of the soil, and especially by the impedance contrast among shallow seismic units. Accordingly, maps of natural frequency are of utmost importance because they allow to recognize areas characterized by a high impedance contrast where a greater amplification in ground motion is expected to occur in case of seismic shaking. Indeed, if the amplified frequency at a site is close to that of a standing or planned building, a resonance effect may occur and therefore the risk for the building to suffer structural damage greatly increases (e.g. Mucciarelli et al. 2001; Castellaro et al. 2014). At this regard, amplification maps are crucial for urban planners in defining the height of buidings (viz. the number of floors) characterized by a resonance coincident with the natural one and enabling engineers to improve the antiseismic behaviour of new constructions or to retrofit old ones. Seismic amplification is in fact considered the first cause of damage and collapse during an earthquake (e.g. Mucciarelli et al. 2001; Gallipoli et al. 2004)

Horizontal to Vertical Spectral Ratio (HVSR) Measurements in the Mirandola anticline area (Northern Italy)

The Mirandola anticline represents a buried fault-propagation fold which has been growing during Quaternary due to the seismogenic activity of a blind segment belonging to the broader Ferrara Arc. The last reactivation occurred during the May 2012 Emilia sequence. In correspondence with this structure, the thickness of the marine and continental deposits of the Po Plain foredeep is particularly reduced. In order to better define the shallow geometry of this tectonic structure, and hence its recent activity, we investigated in a depth range which is intermediate between the surficial morphological observations and seismic profiles information. In particular, we carried out numerous passive seismic measurements (single-station microtremor) for obtaining the horizontal-to-vertical spectral ratio. The results of a combined analysis of the peak frequency and its amplitude nicely fit the available geological information, suggesting that this low-cost geophysical technique could be successfully applied in other sectors of wide morphologically flat alluvial plains to investigate blind and completely buried potential seismogenic structures. The complete dataset of 131 measurements, with HVSR curve in jpg format and peak frequency and amplitude of the ratio H/V values, is here provided

Il complesso sistema di sorgenti sismogeniche nell'area ferrarese e i loro effetti nella storia.

Nel maggio 2012, due terremoti di magnitudo moderata, seguiti da un importante sciame sismico, hanno coinvolto il settore orientale della Pianura Padana. In questa nota si vuole illustrare in modo sintetico il complesso sistema di strutture tettoniche che si trovano sotto i nostri piedi e che, nel loro insieme, costituiscono il prolungamento settentrionale dell’orogene appenninico attualmente sepolto e ‘nascosto’ dalle coltri alluvionali della Pianura Padana. Il settore più esterno di questa catena montuosa è rappresentato da un sistema di sovrascorrimenti disposti a geometria arcuata: il cosiddetto Arco Ferrarese. Gli eventi sismici del maggio 2012 ed alcuni dei maggiori terremoti storici che hanno colpito Ferrara nei secoli precedenti sono stati causati proprio dalla riattivazione di alcuni segmenti appartenenti a tale complesso sistema deformativo. Quando si verificherà il prossimo evento e dove esattamente non possiamo prevederlo con esattezza ma, visto il contesto tettonico e geodinamico, il fenomeno si ripeterà certamente nel futuro ed è pertanto opportuno fare prevenzione

Information technology tools for the valorisation of seismology’s historical documentary heritage

In the past few decades historical documentation of a scientific and non-scientific nature has taken on critical importance in the different sectors of seismology: historical seismology and historical seismometry. Modern technologies offer unique opportunities for cataloguing and efficiently distributing the reproductions or digital versions of scientific letters. Over the last 20 years SGA (Storia Geofisica Ambiente) has set up and promoted, within the scope of the TROMOS (INGV-SGA) and EUROSEISMOS (INGV-SGA) projects, initiatives for the cataloguing, reproduction, study and dissemination of documentation relating to the history of seismology in both Italy and Europe. This approach, based on the application of modern technologies, has enabled us to achieve a rigorous processing and study of documents using the most appropriate information technology tools. The techniques we have used encourage the dissemination and study of historical scientific documentation seeking to bring together scholars and research groups within a new disciplinary community dedicated to studying the history of earth sciences