HR: 1340h
AN: S33A-1074    [Abstracts]
TI: Seismic Imaging of the Corinth Rift Structure (Greece) From Converted Waves Migration of Local Earthquake Recordings
AU: * Latorre, D
EM: latorre@geoazur.unice.fr
AF: UMR G\'eosciences Azur, 250 rue Albert Einstein, Valbonne, 06560 France
AU: Virieux, J
AF: UMR G\'eosciences Azur, 250 rue Albert Einstein, Valbonne, 06560 France
AU: Monfret, T
AF: UMR G\'eosciences Azur, 250 rue Albert Einstein, Valbonne, 06560 France
AB: In the last 20 years, different models have been proposed to explain extensional mechanisms of the Corinth Rift (Greece) based on various data information. In these models, seismic information plays a central role both in terms of seismicity and velocity model imaging. In order to improve our knowledge of the seismic velocity structure of the Corinth Rift, we have analyzed converted waves using micro-earthquake recordings of a two-months seismological experiment performed in 1991. We have applied a prestack depth migration, based on a 3D Kirchhoff summation technique. Kinematic ingredients of the Kirchhoff approach are obtained from P and S smooth velocity structures reconstructed from hypocenter and velocity tomography of first-arrival times. Traveltimes locate recorded amplitude on seismograms which are summed with weights. These weights include geometrical spreading along rays and Snell coefficients at the diffraction point. We have analyzed 637 micro-earthquakes recorded at a network of 17 three-component stations deployed in the western Gulf of Corinth. The obtained PS forward-scattered image, which has an higher frequency content than tomographic models, indicates the presence of a strong reflector at 7-9 km depth beneath the rift. This interface may be correlated with the presence at depth of the Phyllades Nappes which is an inherited structure of the Hellenic orogenic belt. In this case, the 7-9 km reflector would be a strong constraint for any geodynamic modeling of the Corinth Rift.
DE: 9335 Europe
DE: 8109 Continental tectonics--extensional (0905)
DE: 7205 Continental crust (1242)
DE: 0905 Continental structures (8109, 8110)
DE: 0935 Seismic methods (3025)
SC: Seismology [S]
MN: 2004 AGU Fall Meeting