HR: 1340h
AN: T13A-0445    [Abstracts]
TI: Seismic Anisotropy in Southern Tyrrhenian Subduction Zone (Italy) from Shear Wave Splitting.CAT/SCAN Project Preliminary Results.
AU: * Baccheschi, P
EM: baccheschi@ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata, Rome, ITA 00143 Italy
AU: Margheriti, L
EM: margheriti@ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata, Rome, ITA 00143 Italy
AU: Steckler, M
EM: steckler@ldeo.columbia.edu
AF: Lamont Doherty Earth Observatory (LDEO), Columbia University, 61 Route 9W, Palisades, NY 10964 United States
AU: Lerner-Lam, A
EM: lerner@ldeo.columbia.edu
AF: Lamont Doherty Earth Observatory (LDEO), Columbia University, 61 Route 9W, Palisades, NY 10964 United States
AU: Armbruster, J
EM: armb@ldeo.columbia.edu
AF: Lamont Doherty Earth Observatory (LDEO), Columbia University, 61 Route 9W, Palisades, NY 10964 United States
AU: Amato, A
EM: amato@ingv.it
AF: Lamont Doherty Earth Observatory (LDEO), Columbia University, 61 Route 9W, Palisades, NY 10964 United States
AB: We present shear wave splitting measurements in the Calabrian arc-Tyrrhenian basin subduction system. The data analyzed consist of several teleseisms and local earthquakes recorded at the CAT/SCAN temporary network (40 stations) and at the INGV national network (15 CESIS and MEDNET networks stations) from 2003 to 2005. We analyzed SKS phases of earthquakes with distance greater than 85° and magnitude greater than 6 and local S phases from slab earthquakes (deeper than 150 km). We used the method of Silver & Chan (1991) to obtain shear wave splitting parameters: fast direction and delay time. The splitting parameters, with delay time up to 2.0 s., reveal the presence of strong seismic anisotropy in the mantle beneath Southern Italy. The SKS show prevalent fast directions oriented NE-SW in the Calabrian. To the north, rotate to NNW-SSE, following the strike of the Southern Apennines mountains.This pattern suggests the presence of strained material in the mantle in and below the slab due to the eastward rollback of the slab. The local S phases, in contrast, show considerably more variability in the fast directions and smaller delay times, suggesting a frequency dependence of the anisotropy and a complex upper mantle deformation in front (i.e. Tyrrhenian side) of the slab.
DE: 7208 Mantle (1212, 1213, 8124)
DE: 7240 Subduction zones (1207, 1219, 1240)
DE: 7294 Seismic instruments and networks (0935, 3025)
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
SC: Tectonophysics [T]
MN: Fall Meeting 2005