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  • 1
    Electronic Resource
    Electronic Resource
    Upper Mantle Anisotropy in Victoria Land (Antarctica) (1998)
    Springer
    Pure and applied geophysics 151 (1998), S. 433-442 
    Details
    ISSN: 1420-9136
    Keywords: Key words: Seismic anisotropy, upper mantle, Antarctica.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract —During the Austral Summers 1993–94 and 1994–95, we operated two temporary seismic arrays in the Victoria Land region, Antarctica. The first was located around the Mt. Melbourne volcano, near Terra Nova Bay, and the second southward, along the ACRUP1 Geotraverse. The aim of these experiments was to provide additional constraints on the Moho geometry and on lithosphere-astheno sphere structure in this zone. For this reason, a number of techniques were applied to recorded teleseismic data. In this paper we describe the results of the analysis on SKS- and S-wave splitting, which show the presence of seismic anisotropy. Computed fast polarization directions range, on average, between 131° and 166°, and delay times are on the order of 1 s. We presume that anisotropy is mainly located in the upper mantle, although we cannot detect, at present, if a contribution from the crust does exist. The fast polarization direction we determine is quite parallel to the opening of the Ross Sea, an active rift system, but also to the Absolute Plate Motion direction. Therefore, we assume that the identified anisotropy may be induced by the extension, activated by plate motion and is still related to it.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s000240050121
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  • 2
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    Regional centroid moment tensor solutions in Cyprus from 1977 to the present and seismotectonic implications (2011)
    Springer
    Details
    Publication Date: 2011-12-06
    Description: We analyzed digital seismic records in order to extend back in time the catalog of regional centroid moment tensors (RCMTs) for the Cyprus region. We applied the analysis and inversion methodology also used for the present-day seismicity on seismograms recorded at regional distance. We computed 18 new regional CMTs of earthquakes of moderate magnitude (4. 8 ≤ M ≤ 5. 5) which occurred in the Cyprus region for the time span 1977-1996. These new focal mechanisms improved the knowledge given by the previously computed solutions carried out by other institutions, as well as the dataset of available earthquake source parameters. The complete focal mechanism database contributed to better define the deformation styles in the study area and to obtain a detailed characterization of the geodynamics of the Cyprus area. New RCMTs support the hypothesis that Cyprus is located in the middle of the transition area from subduction to continental collision along the Africa-Arabian-Eurasian boundary. In particular, data confirm (a) this transition zone is strictly located west of Cyprus, probably related to a tear in the subduction system, and (b) the still active compression in the Cyprus Arc can be seen as a starting point of the continental collision eastward. © 2011 Springer Science+Business Media B.V.
    Print ISSN: 1383-4649
    Electronic ISSN: 1573-157X
    Topics: Geosciences , Physics
    Published by Springer
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  • 3
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    Upper Mantle Anisotropy in Victoria Land (Antarctica) (1998)
    Springer
    Details
    Publication Date: 1998-03-01
    Print ISSN: 0033-4553
    Electronic ISSN: 1420-9136
    Topics: Geosciences , Physics
    Published by Springer
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  • 4
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    Convergence vs. retreat in Southern Tyrrhenian Sea: Insights from kinematics (2007)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: The Tyrrhenian Sea is an extensional basin opened by trench retreat and back-arc extension during subduction of the Calabrian slab in the last 10–12 My. Subduction is still active beneath the SEmost part of the Tyrrhenian Sea, as testified by seismicity down to 500 km depth. By analyzing seismicity and geodetic data, together with recent tomographic images, we define the present-day situation. An evident N-S compressional regime prevails in the Tyrrhenian region west of the Aeolian archipelago, while east of them a NNW-SSE extension is documented by focal mechanisms and GPS data, with a much smaller strain rate with respect to the past. The transition between these two domains is accommodated by a N-S discontinuity zone which runs from Aeolian Islands to Mt. Etna with an extensional to strike-slip deformation.
    Description: Published
    Description: L06611
    Description: JCR Journal
    Description: reserved
    Keywords: geodynamics ; seismotectonics ; 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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    End of subduction in northern Apennines confirmed by observations of quasi-Love waves from the great 2004 Sumatra-Andaman earthquake (2007)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: Surface waves from the great Sumatra-Andaman earthquakes of 2004 and 2005 that cross Italy south of 44 N display Love-to-Rayleigh scattered waves (quasi- Love phases) diagnostic of sharp lateral gradients in the anisotropic properties of Earth’s upper mantle. Surface waves that traverse Italy further north lack this distinctive phase, documenting a change in the upper mantle fabric that is corroborated by a shift in the fast polarization of shear wave birefringence. These observations suggest that orogen-parallel asthenospheric extension behind the retreating Apennines slab has limited geographical expression. We hypothesize that subduction rollback currently terminates at 44 N, while the upper mantle flow pattern further to the north has been recently rearranged.
    Description: Published
    Description: L04304
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: reserved
    Keywords: surface wave ; Sumatra earthquake ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 6
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    Source analysis of the February 12th 2007, MW 6.0 Horseshoe earthquake: Implications for the 1755 Lisbon earthquake (2007)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: While very large earthquakes are generally confined to subduction zones, the SW Iberian margin –setting of the famous Mw 8.5–8.7, 1755 Lisbon tsunami earthquake- may be an exception to this rule. Evidence for active subduction is not conclusive here, but instead plate convergence in old oceanic lithosphere with large brittle layer thickness can account for the occurrence of great earthquakes along moderate-length faults. We estimate the source parameters of the February 12th 2007, Horseshoe earthquake. Regional moment tensor inversion yields an Mw 6.0, reverse to strike-slip faulting source in the upper mantle. Modelling teleseismic, surface-reflected body waves (pP, pwP, sP) indicates a source depth of 40 km beneath the seafloor. Analysing apparent source time functions allows identifying the preferred fault plane (strike N245°E/ dip 55°/ rake 50°), and estimating rupture area (53 km2) and average slip (0.27 m). Scaling the source characteristics to the size of the 1755 earthquake suggests a fault length of 230–315 km, being compatible with the length of mapped faults in the area.
    Description: Published
    Description: L12308
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: source mechanisms ; tsunamigenic sources ; 01. Atmosphere::01.02. Ionosphere::01.02.05. Wave propagation
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 7
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    Abrupt change in mantle fabric across northern Apennines detected using seismic anisotropy (2007)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: We estimated SKS splitting parameters for 18 earthquakes observed over 2 years on a dense linear seismometer array crossing the Apennines orogen (Northern Italy). An abrupt (within 30 km) change in fast polarization occurs near the crest of the Apennines. Southwest of the crest, fast polarization parallels the Apennines strike (WNW–ESE), rotating to EW orientation near the Tyrrhenian Sea. Northeast of the crest, toward the Po Plain, fast polarization is NNE–SSW, roughly normal to the orogen’s strike. Delay times (0.6–2.9s) do not show a remarkable pattern. Splitting parameters beneath the Apennines argue against anisotropy restricted to the crust, and suggest that the mantle region deformed by Apennines slab rollback is spatially limited. We hypothesize that the rollback process has been uneven, evolving to a contortion of the northern edge of the Apennines slab, and perhaps incipient detachment. Lithospheric anisotropy beneath the Po-Plain may also be significant.
    Description: Published
    Description: L07308
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: reserved
    Keywords: anisotropy ; subduction ; 05. General::05.02. Data dissemination::05.02.02. Seismological data
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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