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  • 1
    Publication Date: 2020-02-06
    Description: At the eastern end of the Azores-Gloria transform fault system to the southwest of Portugal, the plate boundary between Africa and Iberia is a region where deformation is accommodated over a wide tectonically-active area. The region has unleashed large earthquakes and tsunamis, including the Mw ~ 8.5 Great Lisbon earthquake of 1755. Although the source region of the 1755 earthquake is still disputed, most proposals include a source location in the vicinity of the Horseshoe Abyssal Plain (HAP), which is bounded by the 5000 m high Gorringe Bank (GB). In this study we characterise seismic activity in the region using data recorded by two local networks of ocean-bottom seismometers (OBS). The networks were deployed in the eastern HAP and at the GB. The dataset allowed the detection of 160 local earthquakes. These earthquakes cluster around the GB, to the SW of Cabo Sao Vicente, and in the HAP. Focal depths indicate deep-seated earthquakes, with depths increasing from 20-35 km (mean of 26.1 ± 7.2 km) at the GB to 15-45 km (mean 31.5 km ± 10.5 km) under the HAP. Seismic activity thus extends down to levels that are deeper than those mapped by active seismic profiling, with the majority of events occurring within the mantle. Thermal modelling suggests that temperatures of approximately 600 °C characterise the base of the seismogenic brittle lithosphere at ~45 km depth. The large source depth and thermal structure supports previous suggestions that catastrophic seismic rupture through the lithospheric mantle may indeed occur in the area.
    Type: Article , PeerReviewed
    Format: text
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  • 2
    Publication Date: 2012-02-01
    Description: An Mw 5.9 earthquake occurred beneath the Horseshoe abyssal plain (HAP), offshore southwest Iberia, on 12 February 2007. The region where the earthquake occurred has a high seismogenic and tsunamigenic potential. The purpose of this paper is twofold: (1) to extract information about the source of the earthquake that contributes to the understanding of regional tectonics; and (2) to evaluate the applicability of a fast algorithm to study a moderate earthquake offshore mainland Portugal. We employed the KIWI tools, which implement a multistep inversion algorithm, to infer both the point- and finite-source properties of the earthquake. In order to assess the robustness of our solutions, we performed independent sets of inversions that take different datasets and assumptions (e.g., Green’s functions, passbands, wave types) as inputs. We also performed bootstrap analyses in order to appraise the robustness of the source parameters. We concluded that the 2007 HAP earthquake centroid is located at 35.841°?N, 10.611°?W, at a depth of 39 km. Scalar moment, M0, is consistently retrieved with an average value of 1.00×1018??N??·???m (moment magnitude Mw 5.9). The finite-fault parameters are difficult to resolve given the existing data. Approximately 70% of our bootstrap solutions indicate a true rupture plane that trends west-northwest–east-southeast (strike=128°, dip=46°, and rake=138°). The location and strike of this fault plane coincide with the southwest Iberian margin (SWIM) faults. However, the 46° dip is difficult to reconcile with the subvertical nature of the SWIM faults.
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
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  • 3
    Publication Date: 2012-06-01
    Description: We present a method to assess the uncertainty of earthquake focal mechanisms based on the standard theory of linear inverse problems. We compute the uncertainty of the moment tensor, M, then map it into uncertainties of the strike, dip, and rake. The inputs are: source and station locations, crustal model, frequency band of interest, and an estimate of data error. The output is a six-dimensional (6D) error ellipsoid, which shows the uncertainty of the individual parameters of M. We focus on the double-couple (DC) part of M. The method is applicable both with and without waveforms. The latter is particularly useful for network design. As an example we present maps of DC resolvability for earthquakes in southwest Europe, computed without waveforms. We find that the resolvability depends critically on frequency range and source depth. Shallow DC sources (10 km) are theoretically better resolved than deeper sources (40 km and 60 km). The DC resolvability of a 40-km-deep event improves considerably when the Portuguese network is supplemented by stations in Spain and Morocco. The DC resolvability can be further improved by using a few ocean bottom seismometer (OBS) stations or a dense land network. A dense land network is able to resolve M well in spite of the large azimuthal gap, which spans ∼200°. The theoretical resolution analysis also explains the success of single-station inversions when using a broad frequency range, as exemplified by an application using waveforms of a Mw 6 earthquake offshore Iberia.
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
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  • 4
    Publication Date: 2018-03-21
    Description: GFZ German Research Centre for Geosciences
    Description: Published
    Description: 1T. Deformazione crostale attiva
    Keywords: tectonics ; geophysics ; crustal stress ; in situ stress ; tectonic stress ; crustal stress pattern ; 04.07. Tectonophysics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: web product
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  • 5
    Publication Date: 2021-12-15
    Description: We present an analysis of the reliability of focal mechanisms obtained through moment tensor inversion at the Irpinia Seismic Network, southern Italy. Our analysis is based on the methods proposed by Zahradník and Custódio (2012) and Sokos and Zahradník (2013). We present two different studies: (1) we compute maps of theoretical focal mechanism resolution for the Irpinia region and (2) we study the reliability of the solutions obtained from waveform inversion of five regional earthquakes. Theoretically, we find that when data error is the dominant source of error, focal mechanism resolution is better close to the spots of higher station density rather than at the center of the network. Using real data, we were able to successfully study four of the five regional events, in spite of the large source–station distances (up to ∼280  km) and significant azimuthal gaps (〉319°). We used variance reduction, double‐couple percentage, signal‐to‐noise ratio, condition number, and focal mechanism variability index to assess the quality of the solutions. Our quality assessment is validated by comparison with independent focal mechanism solutions.
    Description: Published
    Description: 1348–1357
    Description: 5T. Sismologia, geofisica e geologia per l'ingegneria sismica
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 6
    Publication Date: 2021-12-22
    Description: Skip Nav Destination RESEARCH ARTICLE| APRIL 07, 2021 Preface to the Focus Section on European Seismic Networks and Associated Services and Products Carlo Cauzzi; Susana Custódio; Christos P. Evangelidis; Giovanni Lanzano; Lucia Luzi; Lars Ottemöller; Helle Pedersen; Reinoud Sleeman Seismological Research Letters (2021) 92 (3): 1483–1490. https://doi.org/10.1785/0220210055 Article history Standard View PDF LinkPDF Cite Share Icon Share Tools Icon Tools Observational seismology in Europe is firmly rooted in national and regional observatories in charge of managing more than 100 permanent seismic networks and more than 200 past and present temporary deployments. Primarily driven by governmental mandates to detect local seismicity and provide earthquake information to civil protection agencies and the general public, this monitoring effort also results in a tremendous amount of high‐quality data—more than 12,000 stations presently contribute to the European Integrated Data Archive (EIDA)—which is made available to scientists and practitioners. This lively community of seismic data providers and users is at the core of the success of this focus section: 30 groups responded enthusiastically to our call for papers, providing high‐quality contributions that describe the state of the art in observational seismology in the greater European region, addressing all components of the life cycle of seismic data, from station design to open dissemination of data and seismological products (Amato et al., 2021; Bono et al., 2021; Bragato et al., 2021; Büyükakpınar et al., 2021; Cambaz et al., 2021; Carrilho et al., 2021; Danecek et al., 2021; Evangelidis et al., 2021; Galea et al., 2021; Heit et al., 2021; Lanzano et al., 2021; Lenhardt et al., 2021; Lund et al., 2021; Mărmureanu et al., 2021; Margheriti et al., 2021; Masson et al., 2021; Mader and Ritter, 2021; Ottemöller et al., 2021; Quinteros, Strollo,et al., 2021; Quinteros, Carter, et al., 2021; Rudzinski et al, 2021; Péquegnat et al., 2021; Schweitzer et al., 2021; Senturk et al., 2021; Shahvar et al., 2021; Spallarossa et al., 2021; Stammler et al., 2021; Strollo et al., 2021; Veikkolainen et al., 2021).
    Description: Published
    Description: 1483–1490
    Description: 5T. Sismologia, geofisica e geologia per l'ingegneria sismica
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 7
    Publication Date: 2023-10-25
    Description: The decryption of the temporal sequence of volcanic eruptions is a key step in better anticipating future events. Volcanic activity is the result of a complex interaction between internal and external processes, with time scales spanning multiple orders of magnitude. We review periodicities that have been detected or correlated with volcanic eruptions/phenomena and interpreted as resulting from external forces. Taking a global perspective and longer time scales than a few years, we approach this interaction by analyzing three time series using singular spectral analysis: the global number of volcanic eruptions (NVE) between 1700 and 2022, the number of sunspots (ISSN), a proxy for solar activity, the polar motion (PM) and length of day (lod), two proxies for gravitational force. Several pseudo-periodicities are common to NVE and ISSN, in addition to the 11-year Schwabe cycle that has been reported in previous work, but NVE shares even more periodicities with PM. These quasi-periodic components range from ~5 to ~130 years. We interpret our analytical results in light of the Laplace's paradigm and propose that, similarly to the movement of Earth's rotation axis, global eruptive activity is modulated by commensurable orbital moments of the Jovian planets, whose influence is also detected in solar activity.
    Description: Published
    Description: 1254855
    Description: OSV2: Complessità dei processi vulcanici: approcci multidisciplinari e multiparametrici
    Description: JCR Journal
    Keywords: worldwide volcanic eruptions, polar motion, sunspot number, planetary orbital moments, Laplace theory, external forcing ; 04.08. Volcanology ; 05.07. Space and Planetary sciences
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 8
    Publication Date: 2023-01-18
    Description: In this article we describe EPOS Seismology, the Thematic Core Service consortium for the seismology domain within the European Plate Observing System infrastructure. EPOS Seismology was developed alongside the build-up of EPOS during the last decade, in close collaboration between the existing pan-European seismological initiatives ORFEUS (Observatories and Research Facilities for European Seismology), EMSC (Euro-Mediterranean Seismological Center) and EFEHR (European Facilities for Earthquake Hazard and Risk) and their respective communities. It provides on one hand a governance framework that allows a well-coordinated interaction of the seismological community services with EPOS and its bodies, and on the other hand it strengthens the coordination among the already existing seismological initiatives with regard to data, products and service provisioning and further development. Within the EPOS Delivery Framework, ORFEUS, EMSC and EFEHR provide a wide range of services that allow open access to a vast amount of seismological data and products, following and implementing the FAIR principles and supporting open science. Services include access to raw seismic waveforms of thousands of stations together with relevant station and data quality information, parametric earthquake information of recent and historical earthquakes together with advanced event-specific products like moment tensors or source models and further ancillary services, and comprehensive seismic hazard and risk information, covering latest European scale models and their underlying data. The services continue to be available on the well-established domain-specific platforms and websites, and are also consecutively integrated with the interoperable central EPOS data infrastructure. EPOS Seismology and its participating organizations provide a consistent framework for the future development of these services and their operation as EPOS services, closely coordinated also with other international seismological initiatives, and is well set to represent the European seismological research infrastructures and their stakeholders within EPOS.
    Description: Published
    Description: DM213
    Description: 3T. Fisica dei terremoti e Sorgente Sismica
    Description: 5T. Sismologia, geofisica e geologia per l'ingegneria sismica
    Description: 6T. Studi di pericolosità sismica e da maremoto
    Description: 8T. Sismologia in tempo reale e Early Warning Sismico e da Tsunami
    Description: 4IT. Banche dati
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 9
    Publication Date: 2022-10-24
    Description: The Earth is a dynamic planet, where earthquakes and volcanoes are among some of its most outstanding expressions. Just like our planet as a whole is subject to lunisolar gravitational tides, seismic and volcanic activity are also influenced by the relative motion of the Sun and Moon. This tidal influence takes different forms, spanning different spatial and temporal scales, from quasiperiodic patterns with semidiurnal to multiannual periods to the triggering of earthquakes and volcanic eruptions. Tidal stresses have been primarily evoked as driving forces, although they are 3–5 orders of magnitude smaller than tectonic stresses, which makes cause-effect relationships elusive. This chapter reviews the different observations of tidal influence in geophysical and geochemical data acquired in tectonic and volcanic settings, as well as the methods that have been developed to detect it. Using case studies, we provide some insights on the sensitivity of geological systems to tidal stresses.
    Description: Published
    Description: 333-364
    Description: 4V. Processi pre-eruttivi
    Keywords: Volcanic activity ; Seismic activity ; Solid Earth and ocean tides ; External forcing ; Tidal triggering ; 04. Solid Earth
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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  • 10
    Publication Date: 2022-11-18
    Description: Seismology and Earthquake Engineering Research Infrastructure Alliance for Europe (SERA), H2020, grant agreements 730900.
    Description: Published
    Description: 2T. Deformazione crostale attiva
    Description: 6T. Studi di pericolosità sismica e da maremoto
    Description: 4IT. Banche dati
    Keywords: Geology ; Earth sciences of Europe ; Earth sciences of Africa ; Earth sciences of Asia ; Earth Sciences and Geology ; earthquakes ; hazard model ; seismogenic faults ; slip rate ; crustal fault sources ; subduction fault sources ; Seismology ; 04.04. Geology ; 04.06. Seismology ; 04.07. Tectonophysics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: web product
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