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  • 1
    Electronic Resource
    Electronic Resource
    Spatio-temporal distribution of seismic activity during the Umbria-Marche crisis, 1997 (2000)
    Springer
    Journal of seismology 4 (2000), S. 377-386 
    Details
    ISSN: 1573-157X
    Keywords: Seismicity ; Central Italy ; Umbria-Marche ; Aftershock sequence ; seismic crisis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract We present the spatio-temporal distribution of more than 2000 earthquakesthat occurred during the Umbria-Marche seismic crisis, between September 26and November 3, 1997. This distribution was obtained from recordings of atemporary network that was installed after the occurrence of the first two largest shocks (Mw =, 5.7, Mw = 6.0) of September 26. This network wascomposed of 27 digital 3-components stations densely distributed in theepicentral area. The aftershock distribution covers a region of about 40 km long and about2 km wide along the NW-SE central Apennines chain. The activity is shallow,mostly located at less than 9 km depth. We distinguished three main zonesof different seismic activity from NW to SE. The central zone, that containsthe hypocenter of four earthquakes of magnitude larger than 5, was the moreactive and the more complex one. Sections at depth identify 40–50°dipping structures that agree well with the moment tensor focalmechanisms results. The clustering and the migration of seismicity from NW to SE and the generalfeatures are imaged by aftershock distribution both horizontally and at depth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026568419411
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  • 2
    Electronic Resource
    Electronic Resource
    Foreshock sequence of September 26th, 1997 Umbria-Marche earthquakes (2000)
    Springer
    Journal of seismology 4 (2000), S. 387-399 
    Details
    ISSN: 1573-157X
    Keywords: dilatancy model ; foreshock ; Vp/Vs variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract On September 3rd (22:07 UTC), 1997 a small earthquake with Mw=4.54 started the foreshocks sequence (≈1500 events with ML 〈3.1) of the September 26th seismic sequence. Two days after, three seismic stations of the University of Camerino were installed around the macroseismic epicenter of the foreshock. We present in this paper the location of foreshocks (with 2.1〈ML〈3.3) which occurred between September 3rd and 26th. Foreshocks location, with horizontal (ERH) and vertical (ERZ) error less than 1.5 km, define an area ≈4 km large. Foreshocks have been localized between the epicenters of the two major events of September 26th, which occurred at 00:33 UTC with Mw=5.6 and at 09:40 UTC with Mw=6.0 (Amato et al., 1998; Ekström et al., 1998). In a vertical cross-section, hypocenters show a low angle (≈30°) structure with SW dip-direction. Focal mechanisms for three of the major events show dip-slip fault solutions with strike direction of about N130, in agreement with the CMT solutions of September 3rd and September 26th earthquakes (Ekström et al., 1998). Data recorded at two stations Popola (POP) e Capodacqua (CPQ) located on the rupture area of the September 26th faults, allowed us to calculate a mean Vp/Vs ratio of 1.84±0.03 for the foreshock. This value is lower than the Vp/Vs ratio of 1.89±0.02 calculated for the aftershock sequence occurred in the same area. Besides, the Vp/Vs ratio during the foreshocks sequence is not stable in time but it seems to increase approaching September 26th. After September 26th mainshocks, this value tends to stabilize around a higher value of 1.89. Following the dilatancy model, we suggest that the relative low Vp/Vs ratio before the main shocks could indicate the presence of fluid in the focal volume. The presence of fluids could have increased the effective stress on the fault plane and could be responsible for the long foreshock activity before the two main earthquakes of September 26th. Therefore, we suggest that this foreshock activity could have also contributed to reduce the friction along the September 26th fault plane, breaking the active structure in two smaller segments. In this hypothesis, foreshock activity could have drastically contributed to mitigate the seismic potential of the Colfiorito's active structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026508425230
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  • 3
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    Shear wave splitting of the 2009 L'Aquila seismic sequence: fluid saturated microcracks and crustal fractures in the Abruzzi region (Central Apennines, Italy) (2016)
    Oxford University Press
    Details
    Publication Date: 2016-02-05
    Description: The Abruzzi region is located in the Central Apennines Neogene fold-and-thrust belt and has one of the highest seismogenic potential in Italy, with high and diffuse crustal seismicity related to NE–SW oriented extension. In this study, we investigate the detailed spatial variation in shear wave splitting providing high-resolution anisotropic structure beneath the L'Aquila region. To accomplish this, we performed a systematic analysis of crustal anisotropic parameters: fast polarization direction ( ) and delay time ( t ). We benefit from the dense coverage of seismic stations operating in the area and from a catalogue of several accurate earthquake locations of the 2009 L'Aquila seismic sequence, related to the M w 6.1 2009 L'Aquila main shock, to describe in detail the geometry of the anisotropic volume around the active faults that ruptured. The spatial variations both in and t suggest a complex anisotropic structure beneath the region caused by a combination of both structural- and stress-induced mechanisms. The average is NNW–SSE oriented (N141°), showing clear similarity both with the local fault strike and the SH max . In the central part of the study area fast axes are oriented NW–SE, while moving towards the northeastern and northwestern sectors the fast directions clearly diverge from the general trend of NW–SE and rotate accordingly to the local fault strikes. The above-mentioned fault-parallel distribution suggests that the observed anisotropy is mostly controlled by the local fault-related structure. Toward the southeast fast directions become orthogonal both to strike of the local mapped faults and to the SH max . Here, are predominantly oriented NE–SW; we interpret this orientation as due to the presence of a highly fractured and overpressurized rock volume which should be responsible of the 90° flips in and the increase in t . Another possible mechanism for NE–SW orientation of in the southeastern sector could be ascribed to the presence of a buried, deep NE–SW oriented fault system. t , both unnormalized and normalized, does not show any clear evidence of increasing with increasing depth indicating that the anisotropy is confined primarily to the shallower crustal layers (~10 km depth). Interpolating t show that higher values are found at the edges of the main patches of the rupture related to the 2009 main shock, while lower values are limited in the central part of the fault plane, where the coseismic slip was higher. We infer that in the areas surrounding the ruptured region, lateral variations in material properties caused overpressurized fluid conditions, while within the main shock ruptured area, high energy released produced an open crack system such that overpressurization was not possible.
    Keywords: Seismology
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 4
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    Rapid response to the earthquake emergency of May 2012 in the Po Plain, northern Italy (2012)
    In:  Annals of Geophysics
    Details
    Publication Date: 2020-02-12
    Keywords: 550 - Earth sciences
    Type: info:eu-repo/semantics/article
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  • 5
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    Earthquake monitoring in Italy: integration of a temporary seismic experiment into national real-time surveillance, the example of FocusX temporary land-network (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-07-25
    Description: The INGV is the operational center for earthquake monitoring in Italy, it operates the Italian National Seismic Network and other networks at different scales and is a primary node of EIDA for archiving and distributing seismic recordings. INGV provides earthquake information to the Department of Civil Protection and to the public. In the frame of the FOCUS (Fiber Optic Cable Use for seafloor studies of earthquake hazard and deformation) project, we deployed a temporary seismic network, FXLand (1J), for a passive seismological experiment to record regional seismicity and teleseismic events. This experiment aims to improve the detection of seismicity; the accuracy of earthquake locations, and to define the crustal structure of the region. The FXLand network (https://doi.org/10.13127/SD/O5QWM6WJCD) is integrated in real-time into the INGV surveillance system. In the deployment period 23〈sup〉rd〈/sup〉 December 2021- 2〈sup〉nd〈/sup〉 February 2023, 1186 regional events were located and 153 6+ teleseismic earthquakes occurred (terremoti.ingv.it). We present the analysis of three seismic sequences: one starting on December 23〈sup〉rd〈/sup〉 2021 with a magnitude 4.3 near Catania lasting about ten days, one occurred in the Messina Strait on May31st June 1〈sup〉st〈/sup〉 2022, the third one in the Ionian Sea from February to April 2022. We applied a template matching technique which doubled the number of detected events in the first two sequences; for the seismicity in the Ionian Sea, to improve detection and locations we are awaiting the data from the FXOBS (XH), a network of broadband and short period OBSs deployed in the Ionian Sea.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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  • 6
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    Caratteristiche del Rumore Sismico nei pressi del Rilevatore di Onde Gravitazionali VIRGO (Cascina, Pisa) (2012)
    INGV
    Details
    Publication Date: 2021-05-12
    Description: In questo lavoro si presentano i risultati di uno studio sulle caratteristiche del rumore sismico in prossimità del rilevatore di onde gravitazionali VIRGO (Cascina, Pisa), con particolare riferimento alle vibrazioni associate all’azione di un vicino parco eolico. La valutazione delle componenti spettrali del rumore verosimilmente indotte dagli aerogeneratori è stata effettuata mediante (i) Misure dirette alla base di una turbina, (ii) Correlazione fra le ampiezze spettrali del rumore e la velocità del vento; (iii) Determinazione delle proprietà direzionali da misure multicanale, (iv) Misura dell’attenuazione del segnale con la distanza dal parco eolico. Il disturbo provocato dagli aerogeneratori è particolarmente energetico alla frequenza di 1.7 Hz e, in particolari condizioni, è stato osservato fino a distanze di 11 km dal Parco Eolico. Il decadimento spaziale delle ampiezze ha un andamento complesso, che può essere interpretato in termini di una combinazione fra onde superficiali e onde di volume rifratte ad un’interfaccia profonda (~800 m) fra i sedimenti plio-pleistocenici ed i calcari Miocenici. La risposta locale nei dintorni dell’interferometro è stata investigata utilizzando la tecnica dei rapporti spettrali H/V. Si sono così evidenziate due bande di amplificazione imputabili ad effetti di risonanza legati alla geologia a scala locale: il primo intorno alla frequenza di 0.35 Hz, il secondo fra 0.7 e 2.0 Hz. Entrambi i picchi risultano essere essenzialmente omogenei in tutta l’area di studio, a conferma della sostanziale uniformità della struttura geologica.
    Description: Published
    Description: 1-30
    Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale
    Description: N/A or not JCR
    Description: open
    Keywords: Seismic Noise ; Array Seismology ; Gravity Waves ; 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: article
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  • 7
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    Space and time variation of crustal anisotropy during the 1997 Umbria-Marche, central Italy, seismic sequence (2007)
    Details
    Publication Date: 2020-11-30
    Description: We measure crustal anisotropy parameters from several hundreds of aftershocks (ML 〉2.5) of the 1997 Umbria–Marche seismic sequence which occurred in a carbonatic fold and thrust belt in the shallow crust of central Apennines (Italy). The analysis of shear wave polarization shows clear S-wave splitting with prevalent fast direction ∼140◦N and average delay times of 0.06 s. The observed fast direction is parallel to the strike of the activated normal-fault system and to the maximum horizontal stress (σ 2) active in the region. This is explained by the presence of stressaligned microcracks or stress-opened fluid-filled cracks and fractures within the sedimentary coverage, even if the role of structural anisotropy cannot be completely ruled out since the maximum horizontal stress is subparallel to the major structural features of the area (main thrusts and normal faults). The peculiar spatio-temporal evolution of the seismic sequence gives us also the opportunity to investigate temporal variations of anisotropic parameters. We analyse those seismogramswhose ray paths sample the crustal volume containing two of the major fault zones, before and after the occurrence of normal faulting mainshocks (Mw 〉5).We observe variations of the anisotropic parameters during the days before and after the occurrence of mainshocks and we interpret them in terms of temporal variations of anisotropic parameters. This interpretation is consistent with temporal variations of the local stress condition and of the fluid pressure in the studied crustal volume proposed in the literature. However, since the spatial sampling of the selected ray paths varies with time, we cannot exclude the contribution of spatial variations of anisotropic parameters.
    Description: Published
    Description: 1482–1490
    Description: 4T. Sismicità dell'Italia
    Description: JCR Journal
    Description: open
    Keywords: crustal anisotropy ; fluid-filled cracks ; S-wave polarization. ; 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Format: 506237 bytes
    Format: application/pdf
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  • 8
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    Terremoto in Emilia Romagna: le attività del Pronto Intervento Sismico durante il primo mese di emergenza. Modalità e tempistica (2013)
    Details
    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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  • 9
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    Emergenza “L’Aquila2009”: la campagna di acquisizione dati della Rete Sismica Mobile stand-alone del Centro Nazionale Terremoti (2010)
    Details
    Publication Date: 2021-06-08
    Description: Il 6 aprile 2009 (3.32 locali) un terremoto di Mw 6,3 ha colpito la regione Abruzzo (Italia centrale) producendo un enorme danno alla città de L'Aquila e ai paesi limitrofi causando circa 300 morti e 60.000 senza fissa dimora. A seguito di questo evento sismico, la struttura di Pronto Intervento dell’INGV (Istituto Nazionale di Geofisica e Vulcanologia), si è rapidamente attivata installando in area epicentrale due reti sismiche temporanee (Re.Mo.Tel. in real-time e Re.Mo. in stand-alone) ed il Centro Operativo Emergenza Sismica. In questo lavoro presentiamo come si e’ svolta la campagna sismica della Re.Mo., avente l’obiettivo di acquisire dati di alta qualità e dettaglio per studiare le sorgenti sismiche, l’evoluzione spazio temporale della sequenza e caratterizzare attraverso la microsismicita’ le strutture di faglia attivate ed le proprieta’ del mezzo circostante. Saranno descritte nel dettaglio l’installazione compiuta a poche ore dal mainshock, il suo sviluppo legato all’evoluzione della sequenza sismica, fino alla sua dismissione nel Marzo 2010.
    Description: Istituto Nazionale di Geofisica e Vulcanologia
    Description: Published
    Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale
    Description: open
    Keywords: Instruments and techniques ; Seismic monitoring ; Emergency ; 04. Solid Earth::04.03. Geodesy::04.03.06. Measurements and monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: report
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  • 10
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    Crustal fracturing and presence of fluid as revealed by seismic anisotropy: Case histories from seismogenic areas in the Apennines (Italy) (2012)
    Details
    Publication Date: 2020-12-17
    Description: An automatic analysis code, Anisomat+, was developed, tested and improved to calculate anisotropic parameters: fast polarization direction and delay time. Anisomat+ was applied on data coming from three zones of the Apennines in Italy. For each area, anisotropic parameters have been interpreted to determine the fracture and stress field taking into account the geological and structural settings. It was recognized that average of fast directions are oriented NW-SE at all sites, in agreement with the orientation of maximum horizontal stress and also with the strike of the main fault structures. The mean values of normalized delay time range from 0.005 s/km to 0.007 s/km and to 0.009 s/km, respectively for L'Aquila region, Alto Tiberina Fault area and Val D'Agri basin, suggesting a 3-4% of crustal anisotropy. Moreover, for each area, the spatial distributions of anisotropic parameters are examined, for L’Aquila 2009 seismic sequence also their temporal distribution is discussed.
    Description: Published
    Description: 417-433
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: open
    Keywords: seismic anisotropy ; Earth Crust ; 04. Solid Earth::04.06. Seismology::04.06.07. Tomography and anisotropy
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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