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High resolution imaging of the Hellenic subduction zone


IPGP - Îlot Cuvier


Séminaires Géosciences Marines

Salle 310

Alexandrine Gesret

Ecole des Mines Paris

The Receiver Function (RF) technique, that aims to isolate P to S teleseismic converted waves, is largely used to image seismic discontinuities at depth. In particular, in subduction zones, the subducting crust has often be identified on RF as a Low Velocity Layer (LVL) embedded between the mantle of the overriding plate and the mantle of the subducting lithosphere. In several subduction zones, a high Vp/Vs ratio inside the oceanic crust has been estimated from the arrival times of the forward and backscattered P to S converted waves at the top and bottom of the LVL. A multiscale analysis allows us to illustrate that the LVL characteristics can be misinterpreted for the common frequency range and leads us to quantify the resolvable thickness of a LVL. The arrival times and polarities of the converted waves can also be used to constrain the geometry of interfaces. We develop a probabilistic inversion that allows to retrieve the thickness, the Vp/Vs ratio and the dip of a LVL and also to quantify the uncertainties associated to these inverted parameters. The approach is finally applied to a real data example of teleseismic events recorded at a 3-component seismometer in order to reliably constrain the characteristics of the oceanic crust at the top of the Hellenic subduction. Join Zoom Meeting

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