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| Titel |
3D crustal and lithospheric structure of the Pyrenean orogenic wedge |
| VerfasserIn |
Thomas Theunissen, Sébastien Chevrot, Matthieu Sylvander, Vadim Monteiller, Antonio Villaseñor, Sébastien Benahmed, Marie Calvet |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250075319
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| Zusammenfassung |
| The Pyrenean orogenic wedge is the consequence of the collision between the Iberian
microplate and the southwesternmost part of the Eurasian plate from 55 to 25 Ma (Eocene to
Oligocene). The shortening began since Late Cretaceous, about 100 My ago, leading to about
75 km from the west to 125 km to the east of continental crustal shortening. Before this
period of time, the region was characterized by a sedimentary basin associated with a very
important thinning that later controlled the deformation during the shortening process. Mantle
outcrops are therefore present along and north of the North Pyrenean Fault with a scattered
localization to the west toward the Mauleon basin. Today, the horizontal deformation
rate is very low and the recent seismicity, mainly normal faulting mechanisms, is
certainly caused by coupling between erosion and isostatic readjustments. Images from
seismic reflection, gravity modeling, local and teleseismic seismic waves inversions
and magnetotellurics inversions are in agreement with the subduction of Iberia
beneath Aquitania. The 3D crustal structure reveals the presence of an important
thickening of the continental crust associated with the subduction of the Iberian lower
crust through the north beneath Aquitania at the favor of a detachment. Lateral
variations of the geometry (including that of the Moho) and the wave propagation
properties are important. In order to better analyze waveforms from local, regional or
teleseismic earthquakes and to better constrain the geodynamical evolution of the
Pyrenean chain over the time, PYROPE and TOPO-IBERIA projects were born. Two
temporary seismic arrays (using broadband seismometers), on the French and Spanish
sides, have been deployed between 2010 and 2013. We present here preliminary
results on 3D crustal structures (approximately in the window 40Ë N-45Ë N and
-4Ë E and 5Ë E) from arrival-times of about 20000 earthquakes recorded at about
200 seismic stations between 1978 and 2012 including temporary arrays data. The
travel-time local and teleseismic tomography uses a 3D a priori crustal velocity model
based on all available geophysical data as initial velocity model (Moho, Conrad,
Basement, Topography and P-waves velocity gradients). Additional constraints from
receiver functions and local tomography are used to converge toward the best Moho
solution. The upper-mantle tomography takes into account the crustal structure
from receiver functions to correct travel-times residuals. Combinations of receiver
functions, upper-mantle tomography, 3D crustal tomography (VP and VS) and relocated
seismicity give us new improved 3D images of the deep structures beneath the Pyrenees. |
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