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  • 1
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    Greenland uplift and regional sea–level changes from ICESat observations and GIA modeling (2012)
    Wiley-Blackwell
    Details
    Publication Date: 2020-12-14
    Description: We study the implications of a recently published mass balance of the Greenland ice sheet (GrIS), derived from repeated surface elevation measurements from NASA’s ice cloud and land elevation satellite (ICESat) for the time period between 2003 and 2008. To characterize the effects of this new, high-resolution GrIS mass balance, we study the time-variations of various geophysical quantities in response to the current mass loss. They include vertical uplift and subsidence, geoid height variations, global patterns of sea level change (or fingerprints), and regional sea level variations along the coasts of Greenland. Long-wavelength uplifts and gravity variations in response to current or past ice thickness variations are obtained solving the sea level equation, which accounts for both the elastic and the viscoelastic components of deformation. To capture the short-wavelength components of vertical uplift in response to current ice mass loss, which is not resolved by satellite gravity observations, we have specifically developed a high-resolution regional elastic rebound (ER) model. The elastic component of vertical uplift is combined with estimates of the viscoelastic displacement fields associated with the process of glacial-isostatic adjustment (GIA), according to a set of published ice chronologies and associated mantle rheological profiles. We compare the sensitivity of global positioning system (GPS) observations along the coasts of Greenland to the ongoing ER and GIA. In notable contrast with past reports, we show that vertical velocities obtained by GPS data from five stations with sufficiently long records and from one tide gauge at the GrIS margins can be reconciled with model predictions based on the ICE-5G deglaciation model and the ER associated with the new ICESat-derived mass balance.
    Description: Published
    Description: 1457-1474
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: restricted
    Keywords: Sea level change ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
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    Application of the Post-Widder Laplace inversion algorithm to postseismic rebound models (2006)
    Details
    Publication Date: 2017-04-04
    Description: The computation of global postseismic rebound in a spherically symmetric, stratified, self-gravitating Earth with Maxwell viscoelastic rheology can be carried out semi-analytically with a normal-mode approach. The solution scheme usually involves the application of standard propagator techniques to the equivalent problem in the Laplace domain; to recover the temporal dependence a numerical Laplace anti-transform is required. This step involves the solution of the so-called “secular equation”, whose degree increases linearly with the detail of the stratification modeling, and whose coefficients become extremely ill-conditioned for high harmonic orders. As a result, the practically solvable models are limited to a few viscoelastic layers, and are anyway affected by severe numerical instabilities. To overcome these difficulties, alternative approaches have been explored by several authors, ranging from Runge-Kutta purely numerical integration to the evaluation of Laplace antitransform by a numerical discretization of the Bromwich integral. The Post-Widder algorithm allows the estimation of the Laplace antitransform by sampling numerically the transform on the positive real axis. This method, which has been recently applied to the computation of GIA viscoelastic Love numbers, allows to bypass completely the root-finding procedure while preserving at the same time the analytical normal-mode solution form. In this work, we apply the Post-Widder method to the computation of post-seismic rebound models. We perform a series of benchmarks to optimize the algorithm for speed while checking its stability against earlier results.
    Description: Published
    Description: San Francisco, USA
    Description: open
    Keywords: postseismic deformation ; 04. Solid Earth::04.01. Earth Interior::04.01.05. Rheology ; 04. Solid Earth::04.03. Geodesy::04.03.08. Theory and Models ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Poster session
    Format: 6723426 bytes
    Format: application/pdf
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  • 3
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    Post-seismic rebound of a spherical Earth: new insights from the application of the Post-Widder inversion formula (2008)
    Details
    Publication Date: 2017-04-04
    Description: The post-seismic response of a viscoelastic Earth to a seismic dislocation can be computed analytically within the framework of normal-modes, based on the application of propagator methods. This technique, widely documented in the literature, suffers from several shortcomings; the main drawback is related to the numerical solution of the secular equation, whose degree increases linearly with the number of viscoelastic layers so that only coarse-layered models are practically solvable. Recently, a viable alternative to the standard normal-mode approach, based on the Post–Widder Laplace inversion formula, has been proposed in the realm of postglacial rebound models. The main advantage of this method is to bypass the explicit solution of the secular equation, while retaining the analytical structure of the propagator formalism. At the same time, the numerical computation is much simplified so that additional features such as linear non-Maxwell rheologies can be simply implemented. In this work, for the first time, we apply the Post–Widder Laplace inversion formula to a post-seismic rebound model. We test the method against the standard normal-mode solution and we perform various benchmarks aimed to tune the algorithm and to optimize computation performance while ensuring the stability of the solution. As an application, we address the issue of finding the minimum number of layers with distinct elastic properties needed to accurately describe the post-seismic relaxation of a realistic Earth model. Finally, we demonstrate the potentialities of our code by modelling the post-seismic relaxation after the 2004 Sumatra–Andaman earthquake comparing results based upon Maxwell and Burgers rheologies.
    Description: Published
    Description: 672-695
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: partially_open
    Keywords: Numerical solutions ; Transient deformation ; Rheology: mantle ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 4
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    A sea level equation for seismic perturbations (2010)
    Details
    Publication Date: 2017-04-04
    Description: Large earthquakes are a potentially important source of relative sea level variations, since they can drive global deformation and simultaneously perturb the gravity field of the Earth. For the first time, we formalize a gravitationally self–consistent, integral sea level equation suitable for earthquakes, in which we account both for direct effects by the seismic dislocation and for the feedback from water loading associated with sea level changes. Our approach builds upon the well established theory first proposed in the realm of glacio–isostatic adjustment modeling. The seismic sea level equation is numerically implemented to model sea level signals following the 2004 Sumatra–Andaman earth- quake, showing that surface loading from ocean water redistribution (so far ignored in post–seismic deformation modeling) may account for a significant fraction of the total computed post–seismic sea level variation.
    Description: Published
    Description: 88-100
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: open
    Keywords: sea-level change ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 5
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    Application of the Post-Widder Laplace inversion algorithm to postseismic rebound models (2010)
    Details
    Publication Date: 2017-04-04
    Description: The postseismic response of a viscoelastic Earth can be computed analytically with a normal-mode approach, based on the application of propagator methods. This framework suffers from many limitations, mostly connected with the solution of the secular equation, whose degree scales with the number of viscoelas- tic layers so that only low-resolution models can be practically solved. Recently, a viable alternative to the normal-mode approach has been proposed, based on the Post-Widder inversion formula. This method allows to overcome some of the intrin- sic limitations of the normal-mode approach, so that Earth models with arbitrary radial resolution can be employed and general linear non-Maxwell rheologies can be implemented. In this work, we test the robustness of the method against a stan- dard normal-mode approach in order to optimize computation performance while ensuring the solution stability. As an application, we address the issue of finding the minimum number of layers with distinct elastic properties needed to accurately describe the postseismic relaxation of a realistic Earth model.
    Description: Published
    Description: 197-200
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: open
    Keywords: rheology ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 6
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    A Sea Level Equation for seismic perturbations (2010)
    Details
    Publication Date: 2017-04-04
    Description: Large earthquakes are a potentially important source of relative sea level variations, since they can drive global deformation and simultaneously perturb the gravity field of the Earth. For the first time, we formalize a gravitationally self-consistent, integral sea level equation suitable for earthquakes, in which we account both for direct effects by the seismic dislocation and for the feedback from water loading associated with sea level changes. Our approach builds upon the well-established theory first proposed in the realm of glacio-isostatic adjustment modelling. The seismic sea level equation is numerically implemented to model sea level signals following the 2004 Sumatra–Andaman earthquake, showing that surface loading from ocean water redistribution (so far ignored in post-seismic deformation modelling) may account for a significant fraction of the total computed post-seismic sea level variation
    Description: In press
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: open
    Keywords: sea-level change ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 7
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    Sea-level fluctuations due to subduction: The role of mantle rheology (2008)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: By means of a stratified viscoelastic Earth model we study the effect of sinking slabs on the dynamic topography, the non-hydrostatic geoid and the long-term sea level variations. Sea level fluctuations due to subduction are found to be sensitive to the nature of the 670 km seismic discontinuity and to the rheological layering of the mantle. The response of our model to both a single subduction and a realistic distribution of slabs is studied by a numerical simulation based on a simplified approach. Consistent with previous results, we find that an upper bound to relative sea level time variations associated with the initiation of a new subduction in the upper mantle is ∼0.1 mm/yr. Relative sea level changes driven by the dynamic readjustment of internal mass heterogeneities may thus be comparable with those attributed to other changes in the tectonic regime on a large scale. This confirms the relevance of subduction as an important contributor to long-term sea level fluctuations.
    Description: Published
    Description: 1587–1590
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: reserved
    Keywords: sea level ; geoid ; dynamic topography ; subduction ; viscosity profile ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 8
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    Relative sea level variations caused by subduction (2008)
    Kluwer Academic Publishers
    Details
    Publication Date: 2017-04-04
    Description: By means of a stratified Earth model with viscoelastic rheology, we have studied the long-term global fluctuations of Relative Sea Level (RSL) induced by subducting slabs. We have computed RSL variations for both a single subduction and a realistic distribution of slabs by a numerical simulation based on a simplified model of the subduction process. RSL is determined by the offset between the geoid and the dynamic topography; our analysis demonstrates that the latter provides the prevailing contribution. We have studied, in addition, the effects of rheological stratification upon the amplitude and time-evolution of these two quantities and, consequently, of RSL fluctuations. According to our results, an upper bound for the rate of RSL associated with subduction is of the order of 0.1 mm/yr, in agreement with previous studies. This rate of sea level variation is comparable with that attributed to changes in the tectonic regime on a large scale. This preliminary result corroborates the suggestion by other authors to include subduction in the list of geophysical mechanisms which contribute to long-term RSL fluctuations.
    Description: Published
    Description: 225–238
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: reserved
    Keywords: dynamic topography ; geoid ; sea level ; subduction ; viscosity profile ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 9
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    Isostatic rebound following the Alpine deglaciation: impact on the sealevel variations and vertical movements in the Mediterranean region (2012)
    Wiley-Blackwell
    Details
    Publication Date: 2017-04-04
    Description: The present-day sea level variations and geodetically observed ground deformations in the Mediterranean area are normally ascribed to the combined effect of tectonic or human-driven subsidence and postglacial uplift as a result of the melting of the major Pleistocene ice sheets. However, another potential cause of deformation, only marginally considered to date, is the melting of the glacier that covered the Alps during the last glacial maximum (LGM). The aim of this paper is to predict the long-term sea level variations induced by the melting of both the late-Pleistocene and Alpine ice sheets and compare our results with the relative sea level (RSL) observations available in the Mediterranean region. This task is accomplished solving the sea level equation (SLE) for a spherically symmetric viscoelastic Earth. Our analysis shows that the melting of the Alpine glacier has marginally affected the Holocene sea level variations in the near-field sites in southern France (Marseilles and Roussillon) and the central Tyrrhenian sea (Civitavecchia), and that the RSL predictions are significantly sensitive to the chronology of the remote ice aggregates. The computations, which are performed using a specific mantle viscosity profile consistent with global observations of RSL rise, show that the uplift rate driven by the Alpine isostatic readjustment may account for up to 1/3 of the rates observed at GPS stations in the western portion of the chain. Our results suggest that a thorough modelization of both near- and far-field ice sheets is necessary to gain a better insight into the present-day deformations and sea level variations in the Mediterranean region.
    Description: Published
    Description: 137-147
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: restricted
    Keywords: Alpine glacier ; glacial rebound ; mantle viscosity ; sea level variations ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 10
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    Anomalous secular sea-level acceleration in the Baltic Sea caused by isostatic adjustment (2014)
    Details
    Publication Date: 2017-04-04
    Description: Observations from the global array of tide gauges show that global sealevel has been rising at an average rate of 1.5-2 mm/yr during the last ~150 years [Douglas 1991, Spada and Galassi 2012]. Although a global sea-level acceleration was initially ruled out [Douglas 1992], subsequent studies [Douglas 1997, Church and White 2006, Jevrejeva et al. 2008, Church and White 2011] have coherently proposed values of ~1 mm/year/century [Olivieri and Spada 2013]. More complex non-linear trends and abrupt sea-level variations have now also been recognized. Globally, these could manifest a regime shift between the late Holocene and the current rhythms of sea-level rise [Gehrels and Woodworth 2013], while locally they result from ocean circulation anomalies, steric effects and wind stress [Bromirski et al. 2011, Merrifield 2011]. Although isostatic readjustment affects the local rates of secular sea-level change [Milne and Mitrovica 1998, Peltier 2004], a possible impact on regional acceleration has been so far discounted [Douglas 1992, Jevrejeva et al. 2008, Woodworth et al. 2009] since the process evolves on a millennium time scale [Turcotte and Schubert 2002]. Here we report a previously unnoticed anomaly in the long-term sea-level acceleration of the Baltic Sea tide gauge records, and we explain it by the classical post-glacial rebound theory and numerical modeling of glacial isostasy. Contrary to previous assumptions, our findings demonstrate that isostatic compensation plays a role in the regional secular sea-level acceleration.
    Description: Published
    Description: S0432
    Description: 1T. Geodinamica e interno della Terra
    Description: JCR Journal
    Description: open
    Keywords: Sea-level change ; Glacial isostatic adjustment ; Rheology ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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