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  • Elsevier Science Limited  (8)
Collection
Years
  • 1
    Publication Date: 2021-03-19
    Description: From simple considerations we propose a revision of the AcceleratingMoment Release (AMR) methodology for improving our knowledge of seismic sequences and then, hopefully in a close future, to reach the capability of predicting the main-shock location and occurrence with sufficient accuracy. The proposed revision is based on the introduction of a “reduced” Benioff strain for the earthquakes of the seismic sequence where, for the same magnitude and after a certain distance from the main-shock epicentre, the closer the events the more they are weighted. In addition,we retain the usual expressions proposed by the ordinary AMRmethod for the estimation of the corresponding main-shock magnitude, although this parameter is the weakest of the analysis. Then, we apply the revised method to four case studies in Italy, three of which are the most recent seismic sequences of the last 9 years culminating with a shallow main-shock, and one is instead a 1995–1996 swarm with no significant main-shock. The application of the R-AMRmethodology provides the best results in detecting the precursory seismic acceleration,when comparedwith those found by ordinaryAMR technique.We verify also the stability of the results in space, applying the analysis to real data with moving circles in a large area around each mainshock epicentre, and the efficiency of the revised technique in time, comparing the results with those obtained when applying the same analysis to simulated seismic sequences.
    Description: Published
    Description: 82–98
    Description: 4T. Fisica dei terremoti e scenari cosismici
    Description: JCR Journal
    Description: restricted
    Keywords: Earthquake interaction ; Forecasting and prediction ; Seismicity and tectonics ; Seismic attenuation ; Seismic sequence ; Foreshocks ; 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
    Publication Date: 2017-04-04
    Description: We highlight the existence of an intriguing and to date unreported relationship between the surface area of the South Atlantic Anomaly (SAA) of the geomagnetic field and the current trend in global sea level rise. These two geophysical variables have been growing coherently during the last three centuries, thus strongly suggesting a causal relationship supported by some statistical tests. The monotonic increase of the SAA surface area since 1600 may have been associated with an increased inflow of radiation energy through the inner Van Allen belt with a consequent warming of the Earth’s atmosphere and finally global sea level rise. An alternative suggestive and original explanation is also offered, in which pressure changes at the core–mantle boundary cause surface deformations and relative sea level variations. Although we cannot establish a clear connection between SAA dynamics and global warming, the strong correlation between the former and global sea level supports the idea that global warming may be at least partly controlled by deep Earth processes triggering geomagnetic phenomena, such as the South Atlantic Anomaly, on a century time scale.
    Description: Published
    Description: 129-135
    Description: 3.4. Geomagnetismo
    Description: JCR Journal
    Description: restricted
    Keywords: Earth magnetic field ; South Atlantic Anomaly ; Global Sea Level ; 04. Solid Earth::04.05. Geomagnetism::04.05.05. Main geomagnetic field
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
    Publication Date: 2017-04-04
    Description: We propose a new geomagnetic field model for the Holocene period based on archaeomagnetic and lava flow data, avoiding the use of lake sediment data. The source of data comes from the GEOMAGIA50v2 database which has been updated with the new archaeomagnetic and volcanic studies published during the last 3 years. The model, called SHA.DIF.14k, allows us to analyse the behaviour of the geomagnetic field for the last 14000 years: from 12000 BC to 1900 AD. For the model construction we use the spherical harmonic analysis in space and the penalized cubic B-splines in time. Both spatial and temporal regularization norms are used to constrain the inversion problem and applied at the core-mantle boundary (CMB) to assure the convergence of the model. For the last 3ka, the model predictions agree with those given by the global model ARCH3k.1 and the European model SCHA.DIF.3k. For older epochs, the new model presents a clear improvement in field resolution with respect to other current models of the geomagnetic field for the Holocene. For the last 9ka, the time evolution of the dipolar moment obtained from the dipole field shows a clear minimum between 5500 BC and 3000 BC, and the well-known continuous decreasing trend of the geomagnetic field strength for the last millennium and half. A general view of the time-average evolution of the geomagnetic field flux lobes at the CMB for the northern hemisphere suggests a marked lobe of positive magnetic flux when the dipole moment was maximum. This lobe vanishes when the dipolar field is decreasing. The north polar wander paths of both north magnetic dip and geomagnetic poles were obtained showing an average rate of motion of 5.1 km/yr and 3.7 km/yr respectively. The model shows that the geomagnetic field can be averaged as axial dipolar in ~2000 years within an error of 5º, the typical uncertainty of the palaeomagnetic studies. Finally, and following the recent definition of archaeomagnetic jerks, we found 8 critical events in the time-evolution of the geomagnetic field for the last 8ka characterized by a maximum in the hemispheric asymmetry of the proposed model. The model is available in the Earth Ref Digital Archive at http://earthref.org/ERDA/1897/.
    Description: Published
    Description: 98-109
    Description: 1A. Geomagnetismo e Paleomagnetismo
    Description: JCR Journal
    Description: restricted
    Keywords: geomagnetism ; archaeomagnetism ; geomagnetic field model ; secular variation ; holocene ; 04. Solid Earth::04.05. Geomagnetism::04.05.01. Dynamo theory ; 04. Solid Earth::04.05. Geomagnetism::04.05.02. Geomagnetic field variations and reversals ; 04. Solid Earth::04.05. Geomagnetism::04.05.03. Global and regional models ; 04. Solid Earth::04.05. Geomagnetism::04.05.05. Main geomagnetic field ; 04. Solid Earth::04.05. Geomagnetism::04.05.06. Paleomagnetism
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 4
    Publication Date: 2017-04-04
    Description: The Antarctic Reference Model (ARM) has been here updated using recent geomagnetic data measured over the Antarctic continent from both ground observatories and satellites. This regional geomagnetic model is based on a Spherical Cap Harmonic Analysis (SCHA) of geomagnetic field measurements over a polar cap of 30° half-angle centred at the geographic South Pole, fixing the maximum spatial expansion index kmax=8 and the maximum temporal order of polynomials qmax=4. The importance of updating ARM model lies, for instance, in its usefulness for the reduction of magnetic surveys, performed during the period of model validity over the Antarctica, or for geomagnetic anomaly field estimations. Moreover, so far, ARM still remains the only regional reference magnetic model specifically constructed for the Antarctic continent. The present updated version can be considered valid from 1955.5 to 2010.0 with predictive coefficients up to 2012.0. The model includes the most recent available data but, in contrast to previous versions not only does it take advantage of a stricter selection of satellite data in order to consider even quieter periods of external magnetic activity, but it also includes ground observatory data previous to 1960 going back to 1955.8. Like the previous versions, the new updated model has been tested and compared with major global models to show its reliability over the region under investigation.
    Description: Published
    Description: 13-25
    Description: 3.4. Geomagnetismo
    Description: JCR Journal
    Description: reserved
    Keywords: Spherical cap harmonic analysis ; Magnetic mapping ; Geomagnetic secular variation ; Antarctica ; 04. Solid Earth::04.05. Geomagnetism::04.05.03. Global and regional models
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 5
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    Elsevier Science Limited
    Publication Date: 2017-04-03
    Description: Several fundamental questions (conundrums) about earthquakes and rocks are inexplicable in terms of conventional sub-critical geophysics. These questions have become so familiar that they are now generally accepted as the way earthquakes and rocks behave and are not recognised as presenting conceptual difficulties. These conundrums are resolved by a new understanding of fluid-rock deformation, where fluid-saturated microcracks in almost all rocks are so closely-spaced they verge on failure and hence are highly-compliant critical-systems which impose a range of new properties on conventional sub-critical geophysics. This new understanding of fluid-rock deformation, this New Geophysics, allows earthquakes to be stress-forecast, and has implications and applications to many solid Earth developments.
    Description: Published
    Description: 501–509
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: restricted
    Keywords: Conundrums resolved ; Monitoring stress changes ; Seismic anisotropy ; Shear-wave splitting ; Stress-accumulation ; Stress-relaxation ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous ; 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 6
    Publication Date: 2017-04-04
    Description: We present a review of our work on data acquired by GEOSTAR-class (GEophysical and Oceanographic STation for Abyssal Research) observatories deployed at three EMSO (European Multidisciplinary Seafloor and water-column Observatory; http://www.emso-eu.org) sites in southern European waters where strong geo-hazards are present: the Western Iberian Margin, the Western Ionian Sea, the Marmara Sea, and the Marsili basin in the Tyrrhenian Sea. A procedure for multiparameter data quality control is described. Then we explain why the seafloor is an interesting observation point for geophysical parameters and how it differs from land sites. We consider four interesting geophysical phenomena found at the EMSO sites that are related to geo-hazard. In the first case, we show how unknown seismicity and landslides in the Western Ionian Sea were identified and roughly localised through a single-sensor analysis based on the seismometer. In the second case, we concentrate on the problem of near-coast tsunami generation and describe a Tsunami Early Warning Detection (TEWD) system, tested in the Western Iberian Margin and currently operating in real time at the Western Ionian site. In the third case, we consider two large volcanoes in the central Mediterranean area, Mt. Etna and the Marsili seamount. Signals from the seismometer and gravimeter recorded at the seafloor at 2100 m b.s.l. show various phases of Mt. Etna's 2002–2003 eruption. For the less-known Marsili we illustrate how several indicators coming from different sensors point to hydrothermal activity. A vector magnetometer at the two volcanic sites helps identify the magnetic lithospheric depth. In the fourth and final case, we present a multiparameter analysis which was focused on finding possible correlations between methane seepage and seismic energy release in the Gulf of Izmit (Marmara Sea).
    Description: Published
    Description: 12–30
    Description: 1A. Geomagnetismo e Paleomagnetismo
    Description: 6A. Monitoraggio ambientale, sicurezza e territorio
    Description: JCR Journal
    Description: restricted
    Keywords: European Seas ; Geophysical measurements ; Multiparameter seafloor and water-column observatories ; Data quality analysis ; Geo-hazard ; Tsunami early detection ; 04. Solid Earth::04.05. Geomagnetism::04.05.04. Magnetic anomalies ; 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 ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 7
    Publication Date: 2017-04-04
    Description: The geomagnetic field (GMF) is steadily acting on living systems, and influences many biological processes. In animals, the mechanistic origin of the GMF effect has been clarified and cryptochrome has been suggested as a chemical magnetoreceptor. Here we propose a possible role for the GMF variations in plant evolution.
    Description: Published
    Description: 1-4
    Description: 1A. Geomagnetismo e Paleomagnetismo
    Description: JCR Journal
    Description: restricted
    Keywords: magnetoreception, plant, geomagnetif reversals ; 04. Solid Earth::04.05. Geomagnetism::04.05.02. Geomagnetic field variations and reversals
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 8
    Publication Date: 2022-06-14
    Description: Aiming to understand the physical processes underneath the reversals events of geomagnetic field, different numerical models have been conceived. We considered here the so named ‘‘domino’’ model, an Ising–Heisenberg model of interacting magnetic macrospins aligned along a ring. This model was proposed by Mazaud and Laj (1989) and then applied by Mori et al. (2013) to study geomagnetic field reversals. The long series of the axial magnetic moment (dipolar moment or ‘‘magnetization’’) generated by the ‘‘domino’’ model are empirically studied by varying all model parameters. We present here some results which are slightly different from those given by Mori et al. (2013), and will provide our explanation on the presence of these differences. We also define the set of parameters that supply the longest mean time between reversals. Using this set of parameters, a large number of time series of axial magnetic moment are also generated. After de-noising the fluctuation of these time series and averaging them, we compared the resulting averaged series with the series of axial dipolar magnetic moment values supplied by CALS7k.2, and CALS10k.1b models, finding similar behavior for the all time series. In a similar way, we also compared the averaged 14,000 years long series of dipolar moment with the dipolar magnetic moment obtained by the model SHA.DIF.14k.
    Description: Published
    Description: 9-23
    Description: 1A. Geomagnetismo e Paleomagnetismo
    Description: JCR Journal
    Description: restricted
    Keywords: Geomagnetic reversal ; Geomagentic excrusion ; Domino model ; Secular variation ; Dipolar magnetic moment ; Geodynamo ; 04. Solid Earth::04.05. Geomagnetism::04.05.01. Dynamo theory
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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