Publikationsdatum:
2017-04-04
Beschreibung:
In this paper we present a collection of good quality shear wave splitting measurements in Southern Italy. In
addition to a large amount of previous splitting measurements, we present new data from 15 teleseisms recorded from 2003 to 2006 at the 40 stations of the CAT/SCAN temporary network. These new measurements provide additional constraints on the anisotropic behaviour of the study region and better define the fast directions in the southern part of the Apulian Platform. For our analysis we have selected wellrecorded
SKS phases and we have used the method of Silver and Chan to obtain the splitting parameters: the azimuth of the fast polarized shear wave (φ) and delay time (δt). Shear wave splitting results reveal the
presence of a strong seismic anisotropy in the subduction system below the region. Three different geological and geodynamic regions are characterized by different anisotropic parameters. The Calabrian Arc domain has fast directions oriented NNE–SSW and the Southern Apennines domain has fast directions oriented NNW–SSE. This rotation of fast axes, following the arcuate shape of the slab, is marked by a lack of resolved
measurements which occurs at the transition zone between those two domains. The third domain is identified in the Apulian Platform: here fast directions are oriented almost N–S in the northern part and
NNE–SSW to ENE–WSW in the southern one. The large number of splitting parameters evaluated for events coming from different back-azimuth allows us to hypothesize the presence of a depth-dependent anisotropic
structure which should be more complicated than a simple 2 layer model below the Southern Apennines and the Calabrian Arc domains and to constrain at 50 km depth the upper limit of the anisotropic layer, at least at the edge of Southern Apennines and Apulian Platform. We interpret the variability in fast directions as
related to the fragmented subduction system in the mantle of this region. The trench-parallel φ observed in Calabrian Arc and in Southern Apennines has its main source in the asthenospheric flow below the slab likely
due to the pressure induced by the retrograde motion of the slab itself. The pattern of φ in the Apulian Platform does not appear to be the direct result of the rollback motion of the slab, whose influence is limited to about 100 km from the slab. The anisotropy in the Apulian Platform may be related to an asthenospheric
flow deflected by the complicated structure of the Adriatic microplate or may also be explained as frozen-in lithospheric anisotropy.
Beschreibung:
Published
Beschreibung:
49-67
Beschreibung:
3.3. Geodinamica e struttura dell'interno della Terra
Beschreibung:
JCR Journal
Beschreibung:
partially_open
Schlagwort(e):
Shear wave splitting
;
Subduction
;
Mantle flow
;
Southern Italy
;
04. Solid Earth::04.01. Earth Interior::04.01.02. Geological and geophysical evidences of deep processes
;
04. Solid Earth::04.01. Earth Interior::04.01.03. Mantle and Core dynamics
;
04. Solid Earth::04.06. Seismology::04.06.07. Tomography and anisotropy
;
04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics
;
04. Solid Earth::04.07. Tectonophysics::04.07.06. Subduction related processes
Repository-Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Materialart:
article
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