HR: 0800h
AN: T51D-0772    [Abstracts]
TI: Geomorphic Evidences of Pleistocene Deformations in the Western Pyrenees (France)
AU: * Lacan, P
EM: pierre.lacan@etud.univ-pau.fr
AF: IPRA-MIGP Pau University, UMR 5212, IPRA-BP 1155, Pau, FRA 64013,
AU: Nivière, B
EM: bertrand.niviere@univ-pau.fr
AF: IPRA-MIGP Pau University, UMR 5212, IPRA-BP 1155, Pau, FRA 64013,
AU: Rousset, D
EM: dominique.rousset@univ-pau.fr
AF: IPRA-MIGP Pau University, UMR 5212, IPRA-BP 1155, Pau, FRA 64013,
AU: Sénéchal, P
EM: Pascale.senechal@univ-pau.fr
AF: IPRA-MIGP Pau University, UMR 5212, IPRA-BP 1155, Pau, FRA 64013,
AB: Due to its intraplate position, the on-going tectonic activity of the Western Pyrenees is only revealed by a moderate and diffuse seismicity. This seismicity presents a general E-W pattern and is distributed along the northern flank of the chain in the western part. We focus here on the Arudy area that suffered from one of the major Pyrenean instrumental earthquakes (M=5,1) in 1980.
An early Cretaceous normal fault of the Iberian margin is probably the seismic source of this event. The late Cretaceous inversion of the margin, first in a left-lateral strike-slip mode and then in a more frontal convergence, resulted in a shallow pop-up geometry near Arudy. This pop-up attests of the presence in depth of a crustal discontinuity. The present-day geodynamic arrangement might reactivate this accident in a right lateral mode. This reactivation leads to a strain partitioning between the deep crustal discontinuity and the shallow pop-up that achieved respectively the lateral and frontal components of the displacement.
Folding of Quaternary terrace remnants above the thrusts limiting the pop-up, attests of the Pleistocene activity of the structure. Growth of alluvial depocenters in the footwall of these thrusts revealed by near-surface geophysical surveys (electric tomography and ground penetrating radar) attest too of this activity. This deformation resulted in ca 1500 m long and 5-10 m high folds during the middle to late Pleistocene.
Using a strain partitioning model, this quantification of the near-surface deformation allows to estimate the displacement achieved by the blind crustal discontinuity. So the seismic hazard due to this fault is better constrained.
Project funded by Région Aquitaine and TTI Production.
DE: 8102 Continental contractional orogenic belts and inversion tectonics
DE: 8107 Continental neotectonics (8002)
DE: 8123 Dynamics: seismotectonics
DE: 8175 Tectonics and landscape evolution
DE: 9335 Europe
SC: Tectonophysics [T]
MN: 2007 Fall Meeting