HR: 08:30h
AN: S41C-03    [Abstracts]
TI: Attenuation in the Upper Mantle Beneath the Northern Apennines (Italy) from Teleseismic P- and S-Wave Spectra
AU: Lucente, F P
EM: lucente@ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata, 605, ROME, 00143, Italy
AU: Piccinini, D
EM: piccinini@ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata, 605, ROME, 00143, Italy
AU: DiBona, M
EM: dibona@ingv.it
AF: Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata, 605, ROME, 00143, Italy
AU: Levin, V
EM: vlevin@rci.rutrgers.edu
AF: Rutgers Univ, Wright Geological Laboratory 610 Taylor Road, Piscataway, NJ 08854, United States
AU: * Park, J
EM: jeffrey.park@yale.edu
AF: Dept of Geology and Geophysics, Yale University PO Box 208109, New Haven, ct 06520-8109, United States
AB: We present preliminary results for seismic attenuation in the mantle beneath the Italian region. We estimate P- and S-wave spectral ratios from teleseisms recorded at the temporary broadband seismic network deployed during the RETREAT (Retreating-TRrench, Extension, and Accretion Tectonics) project. We examine body-wave attenuation variation across the northern part of the Apennines mountain belt, which represents the accretionary wedge exposed during recent episodes of the subduction process in Italy. The data recorded during the three-year seismic campaign were analyzed using an ad hoc semi-automated procedure based on the cross-correlation analysis of a single phase across all the stations for each event. The seismic phases analyzed (P, S, SKS) display different patterns of seismic attenuation. Furthermore, we observe systematic variations in the distribution of the attenuation values as function of both the azimuth and the incidence angle of the seismic rays. Relatively high attenuation values are found on the Tyrrhenian side by seismic rays coming from the SW for both P- and S-phases. For NE-approaching rays the pattern of high attenuation values varies considerably, depending on the seismic phases: for P-waves it grossly corresponds to the mountain belt, while for S-waves it extends over almost the whole study area. By correlating attenuation estimates and the velocity structure from the existing tomographic models, we can make some inferences on the thermal state of the sublithospheric mantle, and on the physical properties of the tectonic elements which constitute the subduction system in the region. From the analysis of the P-phases we can clearly distinguish three main areas with different attenuation values, corresponding to the back-arc mantle (high attenuation), to the slab (low attenuation) and to the retro-slab mantle (high attenuation). The correspondence between the identified elements of the subduction system and the S- waves attenuation is not straightforward, and need to be further investigated.
DE: 3909 Elasticity and anelasticity
DE: 7203 Body waves
DE: 7205 Continental crust (1219)
DE: 8109 Continental tectonics: extensional (0905)
DE: 9335 Europe
SC: Seismology [S]
MN: 2007 Fall Meeting