HR: 1340h
AN: T53B-0501    [Abstracts]
TI: Mantle Anisotropy Below the Northern Apennines From RETREAT Seismic Data
AU: * Plomerova, J
EM: jpl@ig,cas.cz
AF: Geophysical Institute, Czech Academy of Sciences, Bocni II/1401, Prague, 14131 Czech Republic
AU: Babuska, V
EM: babuska@ig.cas.cz
AF: Geophysical Institute, Czech Academy of Sciences, Bocni II/1401, Prague, 14131 Czech Republic
AU: Vecsey, L
EM: vecsey@ig.cas.cz
AF: Geophysical Institute, Czech Academy of Sciences, Bocni II/1401, Prague, 14131 Czech Republic
AU: Piana Agostinetti, N
EM: piana@ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia, via Arezzo, Arezzo, 00000 Italy
AU: Piccininni, D
EM: piccininni@ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia, via Arezzo, Arezzo, 00000 Italy
AU: Margheriti, L
EM: margheriti@ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia, via di Vigna Murata 605, Rome, 00143 Italy
AU: Lucente, P
EM: lucente@ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia, via di Vigna Murata 605, Rome, 00143 Italy
AU: Amato, A
EM: amato@ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia, via di Vigna Murata 605, Rome, 00143 Italy
AU: Pondrelli, S
EM: pondrelli@bo.ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia, via Donato Creti 12, Bologna, 40133 Italy
AU: Levin, V
EM: vlevin@rci.rutgers.edu
AF: Rutgers Univ., Dept. of Geological Sciences, 610 Taylor Road, Piscataway, NJ 08854 United States
AU: Okaya, D
EM: okaya@usc.edu
AF: Univ. Southern California, Dept. of Earth Sciences, 133 South Science Bldg, Los Angeles, CA 90089-0740 United States
AU: Park, J
EM: jeffrey.park@yale.edu
AF: Yale Univ., Dept of Geology and Geophysics POB 208109, New Haven, CT 06520-8109 United States
AB: Progressive collision between the Eurasian and African plates is associated with a steady growth of the Apennine mountain range. Simultaneous extension in the convergent margin of the Adriatic and Tyrrhenian domains results in a retreat of the subducting Adriatic plate from the orogenic front caused by sub-lithospheric mantle processes. A study of seismic anisotropy in the mantle around the contact of the two lithospheric domains by the multidisciplinary project RETREAT aims to develop a self-consistent dynamic model of syn-convergent extension in the Northern Apennines. The distribution of seismic anisotropy in the upper mantle, the crust and lithosphere thicknesses, and the location and geometry of the Adriatic slab are specific objectives of the project. We model the large-scale seismic anisotropy due to preferred orientation of olivine by a joint analysis/inversion of body-wave data (P residuals, shear-wave splitting) recorded during the RETREAT field measurement as well as data of permanent INGV observatories. Initial analysis of splitting of core shear waves (SKS) has detected both distinct lateral variations of anisotropic parameters (splitting time delay and the fast shear-wave orientation) and their dependence on the direction of propagation (back azimuth, incidence angle) within the anisotropic upper mantle. Similar to continental regions without an active subduction zone, a significant part of the observed anisotropic signal should be generated by a frozen-in fabric of different lithospheric domains (e.g., terranes or microplates). At domain boundaries, the effective anisotropy should vanish or suffer large spatial variation (e.g., at the Alps-N. Apennines; Adriatic-Tyrrhenian), while within a domain itself it remains consistent. To develop a 3D self-consistent anisotropic model of the upper mantle structure we have to consider both the frozen (or deformed) part of anisotropy within the mantle lithosphere and that part of anisotropy which reflects a sub-lithospheric mantle flow, related to the more viscous high-velocity heterogeneity represented by the subducting plate.
DE: 8102 Continental contractional orogenic belts
DE: 8109 Continental tectonics--extensional (0905)
DE: 7203 Body wave propagation
DE: 7205 Continental crust (1242)
DE: 7218 Lithosphere and upper mantle
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting