Skip to Main content Skip to Navigation
Journal articles

The oceanic nature of the African slab subducted under Peloponnesus: thin-layer resolution from multiscale analysis of teleseismic P-to-S converted waves

Abstract : In the Hellenic subduction zone, the lithospheric slab may comprise continental and oceanic units juxtaposed downdip and along strike. For stations along eastern Peloponnesus, teleseis-mic P-wave receiver-function (RF) processing in the standard frequency band produces an image of a low-velocity layer (LVL) at the top of the slab apparently twice thicker than for an oceanic crust. To assess if this could come from a lack of resolution of the standard processing , we develop a multiscale approach with the RFs based on the wavelet-response of the medium, akin to the wavelet-transform of the velocity-depth function. The synthetic response in conversion is obtained for a multiscale singularity formed by two opposite velocity-steps at the boundaries of a crust embedded in mantle material. This indicates that only wavelet periods shorter than about 0.8 s will allow to identify clearly a 7 km thin oceanic crust. Going to longer periods leads to underestimate or overestimate the time-thickness of the LVL, due to interference phenomena. The analysis of the response in conversion from full waveform synthetic seismograms in a dipping slab model validates a multiresolution approach to real observations. With earthquakes of broad-enough spectrum towards high frequencies, yielding energy to provide wavelet periods significantly shorter than 1 s, the P-to-S conversions obtained allow us to resolve for the first time a standard oceanic crust at the slab top beneath the eastern coast of Peloponnesus. This documents the subduction of a purely oceanic slab of most reduced buoyancy since 4-5 Myr under the rapidly southwestward extending upper plate continental material.
Document type :
Journal articles
Complete list of metadatas

Cited literature [64 references]  Display  Hide  Download

https://hal.archives-ouvertes.fr/hal-00538637
Contributor : Alexandrine Gesret <>
Submitted on : Friday, August 7, 2020 - 5:37:51 PM
Last modification on : Thursday, September 24, 2020 - 4:34:27 PM

File

183-2-833.pdf
Publisher files allowed on an open archive

Identifiers

Citation

Alexandrine Gesret, Mireille Laigle, Jordi Diaz, Maria Sachpazi, Alfred Hirn. The oceanic nature of the African slab subducted under Peloponnesus: thin-layer resolution from multiscale analysis of teleseismic P-to-S converted waves. Geophysical Journal International, Oxford University Press (OUP), 2010, 183 (2), pp.833-849. ⟨10.1111/j.1365-246X.2010.04738.x⟩. ⟨hal-00538637⟩

Share

Metrics

Record views

560

Files downloads

88