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  • 1
    ISSN: 1573-157X
    Keywords: Aftershocks distribution ; Apennines ; earthquake location ; propagation models ; seismic sequences
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract We present some preliminary results obtained from thejoined analysis of the data collected by the permanentand the temporary networks operating in the area ofthe earthquake sequence that followed (andanticipated) the 26 September, Central Italy, mainshocks. In particular, these earthquake data haveallowed us to determine a well constrainedwave-velocity model (both P and S) with stationcorrections which demonstrated to produce robusthypocentral locations. These velocity modelswith station corrections have been used forre-locating the whole September 1997–July 1998subset of data of the permanent network, and theprevious background seismicity, starting from May1996. The focal mechanisms of the largest events werealso obtained from an analysis of the first-motionpolarities.Our results indicate that 1) the seismic activityaligns on a SE-NW trend for a total length of about50 km of extension; 2) the focal depth of theseevents is restricted to the range 0–9 km; 3) mostevents can be related to sub-parallel SW dipping faultplanes; 4) focal mechanisms of the largest shocks(ML 〉 4) show a coherent behaviour, withnormal fault solution on SSE-NNW striking, SW dippingplanes; 5) the space-time evolution of the activitydisplays a discontinuous mode of energy release, withdifferent episodes of activation and an apparentclustering of aftershocks at the edges of the areaswhich presumably ruptured in the main shocks.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-157X
    Keywords: Apennines ; local earthquake tomography ; seismicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract We present some preliminary images of the 3-D P-wavevelocity model and of the relocated seismicityobtained from the data collected by the GNDT-SSNtemporary network installed in the epicentral area ofthe earthquake sequence that followed the 26September, 1997, Central Italy main shock(Mw = 6.0). This network consisted of a total of 15stations, was deployed in the southern part of thearea affected by the earthquake sequence and operatedfor a total of 17 days starting on 10/18/97.Our results indicate that 1) the P-velocity structuredisplays a pattern of lateral variations consistentwith the general NW-SE trend of the Apennines in thearea; 2) the aftershock foci distribute, in thesouthern part of the sequence, on distinct and welldefined SW dipping planes which surface intersectionsmatch previously recognized active normal faults; 3)a distinct zone of aftershock quiescence is observedin correspondence of the 10/12 (ML = 5.3) and10/14/97 (ML = 5.7) hypocenters near Sellano; 4)the seismicity at the southern end is very shallow andit is unclear the relationship between the 1997 andthe 1979 Norcia sequences.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2020-12-15
    Description: no abstract
    Description: Unpublished
    Description: 1.1. TTC - Monitoraggio sismico del territorio nazionale
    Description: open
    Keywords: earthquake location ; source parameters ; 04. Solid Earth::04.06. Seismology::04.06.10. Instruments and techniques
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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  • 4
    Publication Date: 2019-11-04
    Description: Recent seismological studies contribute to better understand the first order characteristics of earthquake occurrence in Italy, identifying the potential sites for moderate to large size earthquakes. Ad hoc passive seismic experiments performed in these areas provide information to focus on the location and geometry of the active faults more closely. This information is relevant for assessing seismic hazard and for accurately constraining possible ground shaking scenarios. The area around the Città di Castello Basin, in the Northern Apennines (Central Italy), is characterized by the absence of instrumental seismicity (M 〉 2.5), it is adjacent to faults ruptured by recent and historical earthquakes. To better understand the tectonics of the area, we installed a dense network of seismic stations equipped with broadband and short period seismometers collecting data continuously for 8 months (October 2000-May 2001). The processing of ~ 900 Gbyte of data revealed a consistent background seismicity consisting of very low magnitude earthquakes (ML 〈 3.2). Preliminary locations of about 2200 local earthquakes show that the area can be divided into two regions with different seismic behaviour: an area to the NW, in between Sansepolcro and Città di Castello, where seismicity is not present. An area toward the SE, in between Città di Castello, Umbertide and Gubbio, where we detected a high microseismicity activity. These findings suggest a probable different mechanical behaviour of the two regions. In the latter area, the seismicity is confined between 0 and 8 km of depth revealing a rather well defined east-dipping, low angle fault 35 km wide that cuts through the entire upper crust down to 12-15 km depth. Beside an apparent structural complexity, fault plane solutions of background seismicity reveal a homogeneous pattern of deformation with a clear NE-SW extension.
    Description: Published
    Description: JCR Journal
    Description: open
    Keywords: microseismicity ; low-angle normalfault ; seismic gap ; seismic hazard ; 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
    Format: 1636129 bytes
    Format: application/pdf
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  • 5
    Publication Date: 2017-05-23
    Description: A seguito della sequenza sismica iniziata il 29 dicembre 2013 con il terremoto di magnitudo (ML) 4.9 alle 16.08 UTC, localizzato tra le province di Caserta e di Benevento dai sismologi in turno presso la sala di sorveglianza sismica [Basili, 2011] dell’Istituto Nazionale di Geofisica e Vulcanologia (INGV), sono stati predisposti diversi interventi volti a migliorare il monitoraggio sismico e geodetico nell’area interessata dalla crisi sismica. L’azione coordinata tra il personale dell’INGV delle sedi di Roma e di Grottaminarda (Avellino) ha consentito, fra le diverse attività, il ripristino delle stazioni sismiche permanenti della Rete Sismica Nazionale (RSN [Amato and Mele, 2008; Delladio, 2011]) esistenti in zona ma mal funzionanti durante le prime ore della sequenza, e l’installazione ex-novo di due stazioni temporanee in trasmissione UMTS a sud-ovest e a sud-est dell’area epicentrale. Benché la copertura dell’area non fosse ottimale, è stato sempre garantito il servizio di sorveglianza sismica avendo localizzato terremoti ben al di sotto della soglia di comunicazione definita nella Convenzione vigente tra INGV e Dipartimento della Protezione Civile (DPC) pari a ML ≥ 2.5. Nelle prime 24 ore della sequenza sono stati infatti localizzati più di 70 terremoti di magnitudo compresa fra 1.0 e 2.0. In questo breve rapporto tecnico sono illustrate, dopo un inquadramento della sequenza sismica e del contesto sismologico in cui si colloca, le considerazioni che hanno portato all’attivazione del Pronto Intervento Sismico INGV, le attività svolte e le tempistiche rispettate.
    Description: Published
    Description: 1-24
    Description: 5T. Sorveglianza sismica e operatività post-terremoto
    Description: N/A or not JCR
    Description: open
    Keywords: Emergency ; Seismic monitoring ; 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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  • 6
    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
    Format: 2579966 bytes
    Format: application/pdf
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  • 7
    Publication Date: 2017-04-04
    Description: Real-time seismology has made significant improvements in recent years, with source parameters now available within a few tens of minutes after an earthquake. It is likely that this time will be further reduced, in the near future, by means of increased efficiency in real-time transmission,increasingdatacoverageandimprovementofthemethodologies.Inthiscontext, together with the development of new ground motion predictive equations (GMPEs) that are abletoaccountforsourcecomplexity,thegenerationofstronggroundmotionshakingmapsin quasi-real time has become ever more feasible after the occurrence of a damaging earthquake. However, GMPEs may not reproduce reliably the ground motion in the near-source region where the finite fault parameters have a strong influence on the shaking. Inthispaperwetestwhetheraccountingforsource-relatedeffectsiseffectiveinbettercharacterizingthegroundmotion.WeintroduceamodificationoftheGMPEswithintheShakeMap softwarepackage,andsubsequentlytesttheaccuracyofthenewlygeneratedshakemapsinpredictingthegroundmotion.ThetestisconductedbycontrollingtheperformanceofShakeMap as we decrease the amount of the available information. We then update ShakeMap with the GMPE modified with a corrective factor accounting for source effects, in order to better constrain these effects that likely influence the level of (near-source) ground shaking. Weinvestigatetwowell-recordedearthquakesfromJapan(the2000Tottori, Mw 6.6,andthe 2008 Iwate-Miyagi, Mw7.0, events) where the instrumental coverage is as dense as needed to ensure an objective appraisal of the results. The results demonstrate that the corrected GMPE can capture only some aspects of the ground shaking in the near-source area, neglecting other multidimensional effects, such as propagation effects and local site amplification.
    Description: Italian Presidenza del Consiglio dei Ministri, Dipartimento della Protezione Civile(DPC)under the contract 2007–2009 DPC-INGVS3project
    Description: Published
    Description: 1836-1848
    Description: 3T. Pericolosità sismica e contributo alla definizione del rischio
    Description: 4T. Fisica dei terremoti e scenari cosismici
    Description: JCR Journal
    Description: restricted
    Keywords: Earthquake ground motions ; Earthquake source observation ; Computational seismology ; 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::04.06.10. Instruments and techniques ; 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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