ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    facet.materialart.
    Unknown
    Effects of the representation of the crustal structure on seismic wave propagation modeling on the continental scal (2011)
    American Geophysical Union, Fall Meeting 2009
    Details
    Publication Date: 2017-04-04
    Description: The representation of crustal structure in 3D numerical models often poses particular problems that are difficult to overcome. Practical implementations of an improved crustal model into efficient tools for seismic wave propagation modeling often fail to honor the strongly varying depth of the Moho discontinuity. The widely used Spectral Element Method (SEM) using hexahedral elements follows the compromise to approximate this undulating discontinuity with polynomials inside the elements. This solution is satisfactory when modeling seismic wave propagation on the global scale and limitedly to rather low frequencies, but may induce inaccuracies or artifacts when working at the continental scale, where propagation distances are in the order of a few hundred or thousand kilometers and frequencies of interest are up to 0.1 Hz. An alternative modeling tool for seismic wave propagation simulations is the Discontinuous Galerkin Finite Element Method (ADER-DG) that achieves high-order accuracy in space and time using fully unstructured tetrahedral meshes. With this approach strong and undulating discontinuities can be considered more easily by the mesh and modifications of the geometrical properties can be carried out rapidly due to an external mesh generation process. Therefore, we implement more realistic models for the European crust -- based on a new, comprehensive compilation of currently available information from diverse sources, ranging from seismic prospection to receiver functions studies -- in both, the SEM and ADER-DG codes, to study the effects of the numerical representation of crustal structures on seismic wave propagation modeling. We compare the results of the different methods and implementation strategies with respect to accuracy and performance. Clearly, an improved knowledge and detailed representation of the structure of the Earth's crust is a key requisite for better imaging of the mantle structure.
    Description: Published
    Description: San Francisco, California, USA
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: open
    Keywords: crust ; wave propagation ; ADER-DG ; SEM method ; Europe ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Poster session
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER (OA)
  • 2
    facet.materialart.
    Unknown
    Analysis of different discrete representations of the European crust for numerical wave propagation simulations (2011)
    EGU General Assembly
    Details
    Publication Date: 2017-04-04
    Description: Implementation of crustal structure challenges accuracy and efficiency of practical numerical solutions of the seismic wave equation. Extremely varying thickness of sedimentary layers and depth of Moho discontinuity create the need for finding viable compromises between speed and precision. We present a study of the influence of different numerical representations of crustal structure on synthetic seismograms. We focus our attention on the European continental scale and consider realistic models for the crust based on a new, comprehensive compilation of currently available information from diverse sources, ranging from seismic prospection to receiver function studies. We investigate different renditions of the Earth structure comparing two approaches: (i) computational meshes honoring the (laterally-varying) geometry of interfaces for a layered crust, and (ii) meshes smoothing out discontinuities of the crustal model within computational elements. The second approach results in computationally more efficient meshes, at the expense of some accuracy in the delineation of the structure, that is however known with some approximation. We compare seismograms, computed using different model discretization accuracies along 2D cross sections, to reference solutions derived from the most accurate structural representation. For the required seismic wave propagation simulations we use the Discontinuous Galerkin Finite Element Method (ADER-DG) providing high-order accuracy in space and time on unstructured meshes. With this approach strong and undulating discontinuities can be considered by the element interfaces and modifications of the geometrical properties can be carried out rapidly due to an external mesh generation process. We analyze the results of the different meshing strategies with respect to accuracy and computational effort. The analysis is based on time-frequency error measures of amplitude and phase misfits and aims at a clear definition of limits in the discretization approach of the crustal structure at the continental scale. Our results are crucial for the creation of computationally more demanding 3D tetrahedral meshes of the model of the European crust in order to understand how much structural detail has actually to be resolved to get sufficiently accurate synthetic data sets in a desired frequency band as this is essential to validate crustal models by comparisons to real seismic observations.
    Description: Published
    Description: Vienna, Austria
    Description: 3.1. Fisica dei terremoti
    Description: restricted
    Keywords: crust ; wave propagation ; ADER-DG ; misfit ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Poster session
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER (OA)
  • 3
    facet.materialart.
    Unknown
    Italian and Alpine three-dimensional crustal structure imaged by ambient-noise surface-wave dispersion (2019)
    Details
    Publication Date: 2019-09-11
    Description: We derive the 3-D crustal structure (S wave velocity) underneath Italy and the Alpine region, expanding and exploiting the database of ambient noise Rayleigh-wave phase- and group-velocity of Ver- beke et al. (2012). We first complement the database of Verbeke et al. (2012) with a dense set of new ambient-noise-based phase-velocity observations. We next conduct a suite of linear least squares inversion of both phase- and group-velocity data, resulting in 2-D maps of Rayleigh-wave phase and group velocity at periods between 5 and 37 s. At relatively short periods, these maps clearly reflect the surface geology of the region, e.g., low velocity zones at the Po Plain; at longer periods, deeper structures such as Moho topogra- phy under Alps and Apennines, and lower-crust anomalies are revealed. Our phase- and group-velocity models are next inverted via the Neighbourhood Algorithm to determine a set of one-dimensional shear- velocity models (one per phase/group-velocity pixel), resulting in a new three-dimensional model of shear velocity (vS) parameterized in the same way as the European reference crustal model EPcrust. We also show S how well vS is constrained by phase and group dispersion curves. The model shows the low velocity area beneath the Po Plain and the Molasse basin; the contrast between the low-velocity crust of the Adriatic domain and the high-velocity crust of the Tyrrhenian domain is clearly seen, as well as an almost uniform crystalline crust beneath the Alpine belt. Our results are discussed from the geological/geodynamical stand- point, and compared to those of other, interdisciplinary studies.
    Description: Published
    Description: 4405-4421
    Description: 1T. Struttura della Terra
    Description: JCR Journal
    Keywords: Italian crust ; Tomography ; surface wave ; ambient noise ; Moho ; 04.06. Seismology ; 04.01. Earth Interior
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER (OA)
  • 4
    facet.materialart.
    Unknown
    Slab Geometry and Upper Mantle Flow Patterns in the Central Mediterranean From 3D Anisotropic P-Wave Tomography (2023)
    Wiley-AGU
    Details
    Publication Date: 2023-02-21
    Description: We present the first three-dimensional (3D) anisotropic teleseismic P-wave tomography model of the upper mantle covering the entire Central Mediterranean. Compared to isotropic tomography, it is found that including the magnitude, azimuth, and, importantly, dip of seismic anisotropy in our inversions simplifies isotropic heterogeneity by reducing the magnitude of slow anomalies while yielding anisotropy patterns that are consistent with regional tectonics. The isotropic component of our preferred tomography model is dominated by numerous fast anomalies associated with retreating, stagnant, and detached slab segments. In contrast, relatively slower mantle structure is related to slab windows and the opening of back-arc basins. To better understand the complexities in slab geometry and their relationship to surface geological phenomenon, we present a 3D reconstruction of the main Central Mediterranean slabs down to 700 km based on our anisotropic model. P-wave seismic anisotropy is widespread in the Central Mediterranean upper mantle and is strongest at 200-300 km depth. The anisotropy patterns are interpreted as the result of asthenospheric material flowing primarily horizontally around the main slabs in response to pressure exerted by their mid-to-late Cenezoic horizontal motion, while sub-vertical anisotropy possibly reflects asthenospheric entrainment by descending lithosphere. Our results highlight the importance of anisotropic P-wave imaging for better constraining regional upper mantle geodynamics.
    Description: This study is supported by the ERC StG 758199 NEWTON.
    Description: Published
    Description: e2021JB023488
    Description: 1T. Struttura della Terra
    Description: JCR Journal
    Keywords: Central Mediterranean ; P‐wave tomography ; mantle dynamics ; seismic anisotropy ; slab geometry ; subduction zone ; 04.01. Earth Interior ; 04.06. Seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER (OA)
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...