Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
1
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
2
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Planning de la Journée des Doctorants
Géosciences Montpellier est un laboratoire reconnu mondialement dans les sciences de la
Terre. La dynamique de la planète est la problématique fondamentale du laboratoire et s’étudie
au travers des différentes enveloppes terrestres. Les chercheurs accueillent et encadrent une
trentaine de doctorants dans des disciplines diverses.
Venez découvrir les travaux de ces jeunes chercheurs en apprentissage.
Présentations
orales
Buffet 12h-14h
: posters
Attention : Les oraux auront lieu dans l’amphithéâtre du bâtiment 23.01. Nous vous invitons à
venir manger entre 12h et 14h, autour d’un buffet et de posters qui permettront des échanges
scientifiques dans un cadre convivial (au niveau du “fer à cheval »).
Cette journée a été organisée, avec le soutien du laboratoire Géosciences Montpellier,
par : Romain Le Roux Mallouf, Céline Baudouin, Manon Dubois, René Chamboredon,
et l’ensemble des Masters 1 et 2 pour les collations.
3
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Sommaire des résumés:
Présentations ................................................................................................. 6
V. Baptiste: Deformation, hydration, and anisotropy of the lithospheric mantle beneath an
active rift: constraints from mantle xenoliths from the North Tanzanian Divergence ......... 7
Y. Caniven: Dynamics of a strike-slip fault analog model: Effects of the tectonic loading rate. . 9
Tectonics of the Western Betics: the role of E-W strike-slip fault corridors ........................... 111
M. Genti: L’érosion nouvelle hypothèse pour l’origine des séismes en France. (Vulgarisation
scientifique) ....................................................................................................................... 133
D. Laurent: Mécanisme de valve sismique associé aux circulations de fluides de bassin :
exemple du Bassin Permien de Lodève (Hérault, France). ................................................ 155
R. Lehu: First estimate of M>6.5 earthquakes records in marine sedimentary archives off East
Taiwan during the last 2,000 years .................................................................................... 177
M. Lejri: Stress inversion assumptions review .......................................................................... 19
A. Moy: Contribution à la modélisation physique du dosage des actinides par microanalyse
électronique. ...................................................................................................................... 211
A. Poujol: Morphotectonics evidence of the 1755 historical earthquake of ........... Fez-Meknes,
Morocco. .............................................................................................................................. 23
Posters ....................................................................................................... 266
V. Baptiste: Petrophysical constraints on the seismic properties of the Kaapvaal craton mantle
root..................................................................................................................................... 277
C. Baudouin Alkaline magmas in early stage rifting - volatile-rich nephelinites from East
African Rift, north Tanzania, Manyara basin. .................................................................... 288
L. Campmas Typhoons driven morphodynamics of the Wan-Tzu-Liao sand barrier (Taïwan) . 30
R. Chailan: A new method for assessing spatial return levels of extreme waves ..................... 31
R. Chamboredon: Fluid inclusions and volatile-rich minerals in nephelinite as tracers of fluids
beneath the NW African Craton (Saghro volcanic field, Anti-Atlas, Morocco) ................. 333
C. Denis: Water content and hydrogen behavior during metasomatism in the uppermost
mantle beneath Ray Pic volcano (Massif Central, France) ................................................ 344
H. El Messbahi: Regional variability of lithospheric mantle beneath the Middle Atlas. ......... 355
L. Fernandez: Positioning the peridotite massifs of north-eastern Algeria in the geodynamic
evolution of the Western Mediterranean: A geochemical and geochronological study
377
B. Fores: Surveillance et modélisation du stockage de l'eau en zone karstique (Larzac, France)
avec un gravimètre supraconducteur. .................................................................................. 39
M. Genti: Could Erosion in the Western Alps triggers large earthquakes in the Ligurian basin?
............................................................................................................................................ 411
F. Gjetvaj: Non – fickian solute transport in heterogeneous medium .................................... 433
4
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
R. Le Roux-Mallouf: Déformation Holocène de l’Himalaya du Bhoutan, apport de la
géomorphologie et de la paléosismologie ......................................................................... 455
A. Marechal: Present-day strain partitioning and strain transfer across the Fairweather and
Denali Faults in SW Yukon – SE Alaska .............................................................................. 477
HN. Nguyen : Déformations extrêmement lentes et mouvement verticaux : apport du GPS et
du nivellement pour contraindre des modèles numériques ............................................... 49
N. Rasendra: Imagerie de l’anisotropie sismique de la croûte – Exemple de la faille de Denali :
localisation de la déformation en profondeur à l’échelle lithosphérique. ........................ 511
F. Rétif : Realistic simulation of instantaneous nearshore water levels during typhoons ..... 533
5
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Présentations
6
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Deformation, hydration, and anisotropy of the lithospheric mantle
beneath an active rift: constraints from mantle xenoliths from the
North Tanzanian Divergence
Virginie BAPTISTE1, [email protected]
Alain Vauchez1, Andréa Tommasi1, Sylvie Demouchy1, Roberta Rudnick2
Géosciences Montpellier, Université Montpellier 2 & CNRS, CC 60, Place E. Bataillon, 34095 Montpellier cedex
5, France
2
Department of Geology, University of Maryland, College Park, Maryland 20742, USA.
1
Keywords: Rift, Peridotite, Deformation, Olivine CPO, Water contents, Anisotropy
We have analyzed the microstructures, the crystal preferred orientations (CPO), and calculated
the seismic properties of 53 mantle xenoliths from four localities within the East African rift
(North Tanzania Divergence), two within the rift axis, and two within the transverse volcanic
belt. OH concentrations in olivine were measured in 15 of these xenoliths.
Most samples have harzburgitic to dunitic compositions, and high olivine Mg#, suggesting
early, extensive partial melting. Within the rift axis, peridotites display mylonitic to
porphyroclastic microstructures, which record deformation by dislocation creep under high
stress, followed by variable, yet weak degrees of annealing. Highly sheared orthopyroxene
crystals in mylonite indicate that the deformation was initiated under high stress and probably
low temperature. However, reactions of replacement of orthopyroxene by olivine observed in
most samples suggest syn-kinematic, near solidus melt-rock reactions. Ubiquituous exsolutions
in orthopyroxene suggest significant cooling between this melt-assisted deformation and
xenolith extraction. Late metasomatism is evidenced by the occurrence of veins crosscutting the
microstructure, as well as the presence of pervasive interstitial clinopyroxene and phlogopite.
Axial-[100] olivine CPO predominates, suggesting the activation of the high temperature, low
pressure [100] (0kl) slip system, coherent with a transtensional deformation. Within the
transverse volcanic belt, Lashaine peridotites display very coarse-granular textures, indicating
deformation by dislocation creep under low deviatoric stress conditions followed by annealing.
The orthorhombic to axial-[010] olivine CPOs are consistent with the simultaneous activation of
[100](010) and [001] (010) slip systems, coherent with a transpressional deformation. Finally,
intermediate microstructures and CPOs are observed in Olmani may indicate a heterogeneous
deformation within the volcanic transverse belt. No systematic variations of olivine OH
concentrations between in axis and off-axis samples are observed. They vary between 2 and 12
ppm wt. H2O, however, the lowest concentrations are measured in mylonites. Maximum P
wave azimuthal anisotropy (AVp) ranges between 3.3 and 18.4% and the maximum S wave
polarization anisotropy (AVs), between 2.3 and 13.2%. The change in olivine CPO symmetry,
from dominantly axial-[100] peridotites from the rift-axis to orthorhombic in xenoliths from
Olmani and axial-[010] in peridotites from Lashaine, results in a variation in the seismic
anisotropy patterns. Comparison between olivine CPOs and SKS fast polarization directions is
consistent with a rift formed by a transtensional deformation.
7
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Legend: Map showing the North Tanzania Divergence and the location of the xenolith
localities.
8
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Dynamics of a strike-slip fault analog model: Effects of the tectonic
loading rate.
Yannick CANIVEN1, [email protected]
Stéphane Dominguez1, Roger Soliva1, Rodolphe Cattin1, Michel Peyret1, Jean Chéry1 and Christian Romano1
1
Université Montpellier II, Lab. Géosciences Montpellier, UMR 5243, Place E. Bataillon, 34095 Montpellier
cedex, France
Keywords: seismic cycles, earthquakes, fault, analog modeling
The average seismic cycle duration extends from hundred to a few thousands years but geodetic
measurements and seismological data extend over less than one century. This short time
observation scale renders difficult to constrain the role of key parameters such as fault friction
and geometry, crust rheology, stress and strain rate that control the kinematics and mechanics of
active faults.
To solve this time scale issue, we have developed a new experimental set-up that reproduces
scaled micro-earthquakes and several hundreds of seismic cycles along a strike-slip fault. The
model is constituted by two polyurethane foam plates laterally in contact, lying on a basal
silicone layer, which simulate the mechanical behaviour of an elastoplastic upper crust over a
ductile lower crust, respectively. To simulate the boundary conditions of a strike-slip fault, a
computerized motoreductor system moves the two compartments on an opposite sens at a
constant low velocity (a few µm/s). The model scaling, deduces from analog material physical
parameters, implies that 1 cm in the model represents 2-3 km in the nature and 1 s is equivalent
to 5-15 years.
Surface-horizontal strain field is quantified by sub-pixel correlation of digital camera pictures
recorded every 16 µm of displacement. We record about 2000 horizontal-velocity field
measurements for each experiment. The analysis of model-interseismic and coseismic surface
displacements and their comparison to seismogenic natural faults demonstrate that our analog
model reproduces correctly both near and far-field surface strains. To compare the experiments,
we have developed several algorithms that allow studying the main spatial and temporal
evolution of the physical parameters and surface deformation processes that characterise the
seismic cycle (magnitudes, stress, strain, friction coefficients, interseismic locking depth,
recurrence time, ...). We also performed surface-velocity field inversions to assess the spatial
distribution of slip and stress at depth along the fault plane.
Our results suggest that far-field boundary-velocity conditions play a key role on the seismic
cycle by influencing rupture sizes, recurrence time and fault behaviour. We observed that low
loading rate generates rare large size characteristic earthquakes and high loading rate numerous
low to moderate magnitude more distributed earthquakes. Our first hypothesis is that this
behaviour may be controlled by the brittle/ductile coupling at the base of foam plates. For a high
strain rate, viscous forces in the silicone layer increase as well as coupling at the base of the
foam plates. These features force the fault to slip at a velocity close to the far field velocity and
induce a more heterogeneous stress field along the fault incompatible with characteristic
earthquake behaviour. For a low strain rate, silicone almost behaves as a newtonian fluid and
viscous forces strongly decrease, allowing the fault to locked and to accumulate more elastic
strain. Stresses are then relaxed by larger seismic events. Another hypothesis is that a part of
this behaviour may be also controlled by a time-dependent static frictional strength.
9
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Figure 1: a) Experimental set-up used to study the seismic cycle on a strike-slip fault ; b) Example of microquake with
horizontal velocity field (top) and displacement amplitude field (down).
Main characteristics events
More Homogeneous slip distribution
Characteristics event
Figure 2 : a) Historical seismicity (top) and corresponding cumulated coseismic offsets (down) for high loading rate (left)
and low loading rate (right).
10
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Tectonics of the Western Betics: the role of E-W strike-slip fault corridors
Gianluca Frasca1, [email protected]
Frédéric Gueydan2, Jean-Pierre Brun1
1
Géosciences Rennes, UMR 6118, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France,
Géosciences Montpellier, UMR 5243, Université Montpellier 2, place E. Bataillon, 34095 Montpellier Cedex 5,
France
2
Keywords: Gibraltar arc, back-arc tectonics, strike-slip faulting.
The arcuate Betic-Rif orogenic belt surrounds the Alboran Sea at the western tip of the
Mediterranean Sea. The tectonic origin of the Betic-Rif chain remains strongly debated.
Here, we investigate the tectonic units cropping out in the Western Betics (Malaga region,
Southern Spain) with the main goal of reconstructing the Oligo-Miocene evolution of the area.
New structural data and geological mapping together with available data allow us to
identify the main structural features of the area. Deformation is found to be extremely diffused
but two E-W elongated tectonic blocks with different lithological composition are outlined by
marked E-W dextral strike-slip corridors ending up in horse-tail splays.
The E-W strike slip corridors are responsible for Miocence tectonics of both the internal and
external zones in the Betic Cordillera.
11
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
12
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
L’érosion nouvelle hypothèse pour l’origine des séismes en France.
(Vulgarisation scientifique)
Manon GENTI1, [email protected]
Jean Chery1, Philippe Vernant1, Rodolphe Cattin1
1
Géosciences Montpellier, CNRS-UM2, Place E. Bataillon, 34095 Montpellier, France
Mots clés : tremblements de terre, érosion
Vulgariser permet de prendre du recul sur ses recherches, et peut de nouvelles idées à
approfondir. Pour ma participation au concours « Ma Thèse en 180 secondes », j’ai pris plaisir à
vulgariser une partie de ma thèse.
Le titre officiel de ma thèse pourra ressembler à : Modélisation numérique de l’influence des
processus de surface sur la déformation de la lithosphère en domaine intraplaque. Pour
vulgariser tout ça j’ai du faire appel à l’imaginaire socio-discursif. La sismicité est un témoin de
la déformation, c’est pourquoi j’ai choisi de toucher le public en m’attaquant aux tremblements
de terre en France.
La France peut être considérée comme un domaine intraplaque, au vu des mouvements
horizontaux données par le GPS. Donc a priori il n’existe pas de forces qui s’opposent ! Cette
observation pose la question de l’origine des séismes en France. Quelles sont les forces qui
s’accumulent sur la faille ?
La localisation des séismes laisse penser qu’il existe un lien entre les montagnes et les séismes.
Deux points supplémentaires sont à retenir : le GPS montre un soulèvement dans les Alpes, et
des indices d’extension sont observés dans les Alpes et les Pyrénées.
Notre équipe de recherche a montré et propose que l’érosion soit le moteur du phénomène qui
permet ces observations. La métaphore utilisée pour expliquer le réajustement isostatique :
l’enlèvement une à une d’une pile de piècettes sur un flotteur dans un verre d’eau.
Avec cette nouvelle hypothèse testée par modélisation numérique 3D, j’espère que dans un an je
ferais trembler le monde de la géologie !
13
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Figure 1 Des forces aux extrémités des blocs font accumuler des contraintes à une faille bloquée. Lorsque la faille ne
résiste plus à ces forces, elle glisse ce qui produit des ondes sismiques et qu'alors la terre tremble!
Figure 2 La flexure vers le haut du trait vert est due au réajustement qu'induit l'érosion. La longueur finale du trait vert
est plus importante que le trait initial (noir pointillé). L’érosion peut être le moteur de l'extension et du soulèvement
observés dans les Alpes.
14
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Mécanisme de valve sismique associé aux circulations de fluides de bassin :
exemple du Bassin Permien de Lodève (Hérault, France).
D. Laurent1, M. Lopez1, A. Chauvet1, M. Thomas2, F. Chevalier2, P. Imbert3, S. Sizaret4, A-C.
Sauvage5, M. Buatier6, A. Gay1
1
Géosciences Montpellier (France) ; 2 TOTAL E&P, Stavanger (Norway) ; 3 TOTAL SA, Pau (France) ; 4 Institut
des Sciences de la Terre d’Orléans (France) ; 5 EGIDE Environnement, Le Horps (France), 6 Laboratoire ChronoEnvironnement, Besançon (France).
Mots clés : fluide, texture, contrôle structural, faille-valve, inclusion fluide, 87Sr/86Sr
Au cours de l’enfouissement des bassins sédimentaires, les fluides interstitiels
initialement piégés au sein de la pile sédimentaire demeurent très mobiles et vont pouvoir
interagir entre eux et avec l’encaissant pendant plusieurs millions d’années. Dans ce contexte,
les zones de failles représentent des drains majeurs qui peuvent être empruntés et réactivés
périodiquement par ces fluides profonds dans des conditions de surpression créant ainsi une
cyclicité des ruptures. Ce mécanisme, dit de « faille-valve », a été principalement décrit dans le
domaine profond (>7km), à la limite avec le domaine métamorphique, mais très peu à l’échelle
d’un bassin sédimentaire.
Le demi-graben Permien de Lodève (Hérault, France), aujourd’hui exhumé, offre des
conditions d’affleurement exceptionnelles permettant d’accéder à des systèmes minéralisés
polymétalliques piégés au sein de failles normales de roll-over affectant les carbonates karstifiés
du Cambrien. Notre approche combine l’étude multi-échelle tectonique/texturale, des inclusions
fluides et géochimiques des corps minéralisés, avec pour principal objectif de décrypter
précisément le modèle mécanique de valve sismique dans la croûte supérieure.
Le remplissage essentiellement barytique se développe de manière cyclique soit dans les failles
ou dans des zones de décollement plus ou moins horizontales parallèles aux plans de
stratification, voire dans des paléokarsts. Trois types de remplissage sont identifiés. L’étude
microthermométrique des inclusions fluides démontre l’existence de fluctuations de pression
fluide dans le domaine supra-hydrostatique et des connexions avec le domaine superficiel au
cours des différents épisodes de minéralisations. Enfin, l’analyse isotopique du strontium ainsi
que les teneurs en éléments traces/terres rares confirment l’origine crustale des fluides à
l’origine des minéralisations ainsi que l’ouverture syntaxiale des zones de faille lors des
précipitations successives.
Cette étude démontre une histoire polyphasée des circulations de fluides dans la zone de
roll-over du Bassin de Lodève : (i) un premier événement lié à l’activation des failles lors du
rifting permien, avec cimentation d’une brèche d’implosion par le fluide qui va réduire la
cohésion du plan de cisaillement, (ii) des réactivations périodiques des plans de failles et
initiation de cisaillement aux interfaces stratigraphiques par la montée en pression de ces mêmes
fluides profonds et (iii) un dernier évènement tectonique syn-rift associé au piégeage des
derniers fluides de bassin et aux hydrocarbures.
Ce travail permet de préciser les conditions de piégeage des fluides ainsi que leur impact
au sein des zones de failles au cours de l’enfouissement des bassins sédimentaires. En
particulier, une dichotomie est mise en évidence entre le contrôle purement tectonique des
migrations de fluides et la réactivation cyclique de plan de cisaillement dans les failles et
parallèlement à la stratification sous la seule action des surpressions de fluide.
15
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Figure 3 : approche intégrée de caractérisation du mécanisme de valve sismique régissant le piégeage des fluides de
bassin.
16
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
First estimate of M>6.5 earthquakes records in marine sedimentary
archives off East Taiwan during the last 2,000 years
Remi Lehu1, 2, [email protected]
Serge Lallemand1,3, Shu-Kun Hsu2,3, Laurent Dezileau1,3, Nathalie Babonneau3,4, Gueorgui
Ratzov5, Andrew T. Lin2,3
1
Geosciences Montpellier, University Montpellier II, France
Department of Earth Sciences, National Central University, Taiwan.
3
LIA,ADEPT, Taiwan-France.
4
Domaines Oceaniques, IUEM, Brest, France
5
IFREMER, Geosciences Marines-LES, Plouzané, France
2
Keywords: Subduction zone-offshore eastern Taiwan-turbidite-historical earthquakes
Large earthquakes are one of the main driving mechanisms for turbidity current generation
along active margins. When the turbidite sequences as well as the trigger mechanisms are well
defined among the sedimentary archives, it is possible to use turbidites records as a proxy for
paleoseismicity investigation. The Taiwan area, where the Philippine Sea Plate collides with the
Eurasian plate at a convergence rate of 80mm/yr, is one of the most seismically active areas in
the world and has been consequently struck repeatedly by destructive earthquakes. To better
constrain the recurrence intervals of large earthquakes, we have conducted two cruises in 2012
and 2013 during which piston cores (up to 4m long) and box-cores were retrieved in tectonically
controlled basin. We aimed at deciphering turbidite units and hemipelagic sequences with
special attention to the source of the turbidites such as river discharges or slope sediments
destabilized by earthquakes. From these cores we analyzed each event using several physical,
chemical and sedimentological proxies. Moreover fine details of vertical elemental distribution
acquired by X-ray fluorescence (XRF) scanning allow us to accurately identify and characterize
turbidite events. Analyzing two cores in the Ryukyu forearc, we have identified 23 beds that
differ from pelagic sediments and interpreted as resulting from slope instabilities. In the Luzon
volcanic arc area, two cores were used to identify 25 layers. 14C dating performed on planktonic
foraminifera and 210Pb-137Cs datings, provide a 2,000-years-long chronology of seismic events.
Precise dating, of the three most recent sedimentary layers of one box-core (36cm long), based
on 210Pb-137Cs and 137Cs chronology provides ages of 2002 ± 3 AD, 1953 ± 4 AD and 1936 ± 8
AD. These ages correspond to large instrumental earthquakes that occurred at a distance less
than 50 km from our sampling site: the 2003 Taitung Earthquake (Mw 6.8), the 1951
Chenggong Earthquake (Mw 7.1) and the 1935 Lutao Earthquake (Mw 7.0). Such a good
correlation between turbidites and (Mw> 6) historical instrumental seismic events suggests that
the record of mass transport deposits can be used as a paleoseismic indicator in this region.
17
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Figure1. Geodynamic context of Taiwan and historical seismicity over the 20th century. Green circles represent M>6.5
earthquakes and green reverse triangles show core sites. DF: Deformation Front, LVF: Longitudinal Valley Fault.
18
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Stress inversion assumptions review
Mostfa Lejri1,2 , [email protected]
Frantz Maerten1 , [email protected]
Laurent Maerten1 , [email protected]
Roger Soliva2 , [email protected]
1
2
Schlumberger – MpTC, Parc Euromédecine, 340 rue Louis Pasteur, 34790 Grabels, France
Géosciences Montpellier, Université Montpellier 2, Place E. Bataillon, 34095 Montpellier cedex 5, France
Wallace (1951) and Bott (1959) were the first to introduce the idea that the slip on each
fault surface has the same direction and sense as the maximum shear stress resolved on that
surface. This hypothesis are based on the assumptions that (i) faults are planar, (ii) blocks are
rigid, (iii) neither stress perturbations nor block rotations along fault surfaces occur and (iv), the
applied stress state is uniform. However, this simplified hypothesis is questionable since
complex fault geometries, heterogeneous fault slip directions, evidences of stress perturbations
in microstructures and block rotations along fault surfaces were reported in the literature. Earlier
numerical geomechanical models confirmed that the striation lines (slip vectors) are not
necessarily parallel to the maximum shear stress vector but is consistent with local stress
perturbations. This leads us to ask as to what extent the Wallace and Bott simplifications are
reliable as a basis hypothesis for stress inversion. In this presentation, a geomechanical multiparametric study using 3D boundary element method (BEM), covering (i) fault geometries such
as intersected faults or corrugated fault surfaces, (ii) the full range of Andersonian state of
stress, (iii) fault friction, (iv) half space effect and (v), rock properties, is performed in order to
understand the effect of each parameter on the angular misfit between geomechanical slip
vectors and the resolved shear stresses. It is shown that significant angular misfits can be found
under specific configurations and therefore we conclude that stress inversions based on the
Wallace-Bott hypothesis might sometime give results that should be interpreted with
care. Major observations are that (i) applying optimum tectonic stress conditions on complex
fault geometries can increase the angular misfit, (ii) elastic material properties, combined to
half-space effect, can enhance this effect, and (iii) an increase of the sliding friction leads to a
reduction of this misfit.
19
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
20
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Contribution à la modélisation physique du dosage des actinides par
microanalyse électronique.
Aurélien MOY1,2, [email protected]
Claude Merlet1, Olivier Dugne2
1
2
GM, CNRS, Université de Montpellier II, Place E. Bataillon, 34095 Montpellier, France.
CEA, DEN, DTEC, SGCS, LMAC, 30207 Bagnols-sur-Cèze, France.
Mots clés : Microanalyse – Actinides – Sans standard – Section-efficace
L’analyse par microsonde électronique (EPMA) est utilisée afin de quantifier, avec une grande
précision, les concentrations chimiques, à l’échelle micrométrique, d’échantillon solide. Elle
permet, par exemple, de quantifier les actinides présents dans les combustibles nucléaires neufs
ou irradiés, d’aider à la gestion des déchets nucléaires ou encore de dater certaines roches.
Malheureusement, ces analyses quantitatives ne sont pas toujours réalisables dû à
l’indisponibilité d’étalons de référence pour certains actinides. Afin de pallier cette difficulté,
une méthode d’analyse dite « sans standard » peut-être employée au moyen d’étalons virtuels.
Ces derniers sont obtenus à partir de formules empiriques ou à partir de calculs basés sur des
modèles théoriques. Toutefois, ces calculs requièrent la connaissance de paramètres physiques
généralement mal connus, comme c’est le cas pour les section-efficaces de production de rayons
X.
Au cours de ce travail, les section-efficaces de production des raies L et M du plomb [1], du
thorium et de l’uranium [2] ont été mesurées par impacts d’électrons sur des cibles minces
autosupportées (d’épaisseur variant de 0,2 à 8 nm) [3]. Les résultats expérimentaux ont été
comparés avec les prédictions théoriques de section-efficaces d’ionisation calculées par Bote et
al. [4] grâce à l’approximation de Born en ondes distordues (DWBA) et avec les prédictions de
formules analytiques utilisées dans les applications pratiques. Les section-efficaces d’ionisation
ont été converties en section-efficaces de productions de rayons X grâce aux paramètres
atomiques extraits de l’ « Evaluated Atomic Data Library » (EADL). Les résultats théoriques du
modèle DWBA sont en excellents accords avec les résultats expérimentaux (Figure a). Ceci
permet de confirmer les prédictions de ce modèle et de valider son utilisation pour le calcul de
standards virtuels. Les prédictions de ce modèle ont été intégrées dans le code Monte Carlo
PENELOPE [5] afin de calculer l’intensité de rayons X produite par des standards pur
d’éléments lourds (Figure b). Les calculs ont été réalisés pour les éléments dont le numéro
atomique est 89 ≤ Z ≤ 99 et pour des tensions d’accélération variant du seuil d’ionisation jusque
40 kV, par pas de 0,5 kV. Pour une utilisation pratique, les intensités calculées pour les raies L
et M les plus intenses ont été regroupées dans une base de données en fonction de la tension
d’accélération.
Les prédictions des standards virtuels ainsi obtenus ont été comparées avec des mesures
effectuées sur des échantillons de composition connue (UO2, ThO2, ThF4, PuO2…) et avec les
données acquises lors de précédentes campagnes de mesures. Le dosage des actinides à l’aide de
ces standards virtuels a montré un bon accord avec les résultats attendus. Ceci confirme la
fiabilité des standards virtuels développés et démontre que la quantification des actinides par
microsonde électronique est réalisable sans standards d’actinides et avec un bon niveau de
confiance.
21
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Légende : a) Résultats expérimentaux et théoriques de la section-efficace de productions des
raies M de l’uranium. b) Spectre calculé et mesuré de la raie U Mα pour un faisceau d’électrons
de 15 kV.
22
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Morphotectonics evidence of the 1755 historical earthquake of
Fez-Meknes, Morocco.
Antoine POUJOL1, [email protected]
Jean-Francois RITZ1, Philippe VERNANT1, Soufian MAATE2, and Abdelilah TAHAYT2
1
2
Université MONTPELLIER 2, GEOSCIENCES, EARTH SCIENCE, MONTPELLIER, France
CNRST, Institut National de Géophysique, Rabat, Morocco
Mots clés: South Rif Front, Fez (Morocco), Morphotectonics, Radiocarbon, "1755" Earthquake
The Southern Rif Front (SRF) is located at the southernmost frontal part of the Rif
Cordillera (Morocco) and overthrusts the foreland basins of Saiss and Gharb. Extending over a
length of ~150km between Fez, Meknes and Rabat cities, the SRF stands out as a major active
structure. It represents an important seismic hazard for these highly-populated cities as
evidenced by their historical seismicity records. The last larger historical earthquake in the area
occurred on the 27 November 1755 (almost a month after the large “Lisbon” earthquake of the
1st November 1755), striking the region of Meknes and Fez and causing many casualties. Its
intensity is reported to be VIII on the MSK scale. Using satellite imagery, aerial photographs
and field investigations, we carried out a morphotectonics study between Fez and Meknes to
identify the most recent traces of tectonic activity. Few kilometres westwards Fez city, we
identified evidence for a very recent reverse fault scarp at the foothills of the Jebel Thrat massif.
High resolution Digital Elevation Model of the fault scarp allowed determining a coseismic
vertical displacement of ~0.75-1m, which yields a reverse slip along the fault of 1.8-2.5 m for a
dip estimated at ~24° towards the North. According to Wells and Coppersmith’s regressive laws
(1994), this amount of displacement yields a Moment Magnitude comprised between 6.5 and 7,
which would correspond to a surface thrust rupture length of ~20-40 km. 14C dating of the
affected stream terrace yields an age of 1700±20 cal AD. These results suggest that the observed
features correspond to the 27 November 1755 historical earthquake. Cumulative deformations
are also observed within the studied area with uplifted, tilted and folded fluvial deposits. In
order to estimate the Holocene long term slip rate along the fault, we mapped an alluvial terrace
showing a 12 m vertical offset, and we sampled its sandy deposits for Optical Stimulated
Luminescence dating.
23
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Field picture of the active South Rif Front (view from the SE - Fez city)
Long-term deformation: folding surface and tilted pebble bed
Recent deformation: "1755AD" historical earthquake thrust scarp
24
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
25
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Posters
26
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Petrophysical constraints on the seismic properties of the Kaapvaal craton
mantle root
Virginie BAPTISTE1, [email protected]
Andréa Tommasi1
1
Géosciences Montpellier, Université Montpellier 2 & CNRS, CC 60, Place E. Bataillon, 34095 Montpellier
Keywords: Peridotite, Craton, Kaapvaal, Anisotropy, Seismic properties
We calculated the seismic properties of 47 mantle xenoliths from 9 kimberlitic pipes in
the Kaapvaal craton based on their modal composition, the crystal preferred orientations (CPO)
of olivine, ortho- and clinopyroxene, and garnet, the Fe content of olivine, and the pressures and
temperatures at which the rocks were equilibrated. These data allow constraining the variation
of seismic anisotropy and velocities within the cratonic mantle. The fastest P and S2 waves
propagation direction and the polarization of fast split shear wave (S1) are always subparallel to
olivine [100] axes maximum concentration, which marks the lineation (fossil flow direction).
Seismic anisotropy is higher for high olivine contents and stronger CPO. Maximum P-wave
azimuthal anisotropy (AVp) ranges between 2.5 and 10.2% and the maximum S-wave
polarization anisotropy (AVs), between 2.7 and 8%. Changes in olivine CPO symmetry result in
minor variations in the seismic anisotropy patterns, mainly in the apparent isotropy directions
for shear wave splitting. Seismic properties averaged over 20 km thick depth sections are,
therefore, very homogeneous. Based on these data, we predict the anisotropy that would be
measured by SKS, Rayleigh (SV) and Love (SH) waves for 5 end-member orientations of the
foliation and lineation. Comparison to seismic anisotropy data in the Kaapvaal shows that the
coherent fast directions, but low delay times imaged by SKS studies and the low azimuthal
anisotropy with SH faster than SV measured using surface waves are best explained by a
homogeneously dipping (45°) foliations and lineations in the cratonic mantle lithosphere.
Laterally or vertically varying foliation and lineation orientations with a dominantly NW-SE
trend might also explain the low measured anisotropies, but this model should also result in
backazimuthal variability of the SKS splitting data, not reported in the seismological data. The
strong compositional heterogeneity of the Kaapvaal peridotite xenoliths results in up to 3%
variation in density and in up to 2.3% variation of Vp, Vs, and Vp/Vs ratio. Fe depletion by melt
extraction increases Vp and Vs, but decreases the Vp/Vs ratio and density. Orthopyroxene
enrichment due to metasomatism decreases the density and Vp, strongly reducing the Vp/Vs
ratio. Garnet enrichment, which was also attributed to metasomatism, increases the density, and
in a lesser extent Vp and the Vp/Vs ratio. Comparison of density and seismic velocity profiles
calculated using the xenoliths’ compositions and equilibration conditions to seismological data
in the Kaapvaal highlights that: (i) the thickness of the craton is underestimated in some seismic
studies and reaches at least 180 km, (ii) the deep sheared peridotites represent very local
modifications caused and oversampled by kimberlites, and (iii) seismological models probably
underestimate the compositional heterogeneity in the Kaapvaal mantle root, which occurs at a
scale much smaller than the one that may be sampled seismologically.
27
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Alkaline magmas in early stage rifting - volatile-rich nephelinites from
East African Rift, north Tanzania, Manyara basin.
Céline BAUDOUIN1, [email protected]
Fleurice PARAT1
1
UMR 5243 – Géosciences Montpellier, UM2 – 2 Place Eugène Bataillon 34095 Montpellier cedex 5
Keywords: Intracontinental Magmas, Early-stage Rifting, Volatiles elements
The narrow rift valley of the East African Rift expands over 200 km, forming the North
Tanzanian Divergence (NTD) and separates 2 geologically distinct areas. (1) In the north, the
Natron basin is characterized by intense magmatic and shallow seismic activity (<10 km). (2) In
the south, the Manyara-Balangida basin is characterized by a scarce volcanic activity: Kwaraha
and Hanang volcanoes, a small cone (Labait), several phreatic maars (Basotu), and deep
earthquake swarms (20-35 km) at the border of the Tanzanian craton. The main aim of my
thesis is to characterize the source and composition of the magmas and fluids present in the
south part of the NTD, and compare them to those within the northern area. This study is part of
a larger geophysical project constraining the percolation of volatile-rich liquids in the lower
crust to better assess the seismic activity.
Alkaline lavas from Kwaraha are mafic (Mg# = 57-66), alkali-poor (Na2O+K2O = 2-5.6 wt.%)
and Ca-rich (CaO > 13 wt.%) nephelinites and carbonatitic lavas (CaO = 62 wt.%). These
nephelinites have a paragenesis with olivine (Fo83-85), cpx (Mg# = 80-87), phlogopite (F = 0.5
wt%, BaO = 0.25 wt.%) and magnetite (Usp = 0.15-0.2). On the other side, Hanang nephelinites
are silica-poor (Mg# = 30-40) and alkali-rich (Na2O+K2O > 10 wt.%) and highly enriched in
incompatibles elements (Sr > 5000 ppm, Nb > 500 ppm). Hanang lavas have a paragenesis with:
nepheline, cpx (Mg# = 40-68), melanite (Ti-Ca Garnet), titanite and magnetite. Melt inclusions
in nepheline indicate volatile-rich silicate liquid with up to 1.2 wt.% F, 0.45 wt.% Cl and 1.8
wt.% SO3.
Two other volcanoes are present south of the NTD: Labait cone (10 km south to Hanang) and
Basotu craters (80 km west to Hanang) with different mineralogy and geochemistry. Labait
lavas are mafic and silica-undersaturated (Mg# = 79, SiO2 < 34.9 wt.%) with olivine (Mg# = 8187), titanite, magnetite (Usp = 0.1), F-apatite (0.05 wt% SO3) and Ni-sulfide (Ni = 5.7 wt.%),
whereas the Basotu craters represent a group of 30 aligned phreatic explosive craters, with
carbonatitic tuff ring (CaO = 41 wt.%).
The petrological and geochemical preliminary studies of lavas from the Manyara-Balangida
basin show strong differences compared to the NTD volcanoes. Lavas from the south part have
more silica-undersaturated and alkaline-rich trends. Moreover, nephelinites are characterized by
the presence of phlogopite phenocrysts (H2O-F-bearing mineral) and volatile-rich melt
inclusions (S, F, and Cl) in nepheline. Complementary analyses in melt inclusions (H2O, CO2,
trace elements) and in situ accessory minerals analyses will be performed to constrain the
composition of fluids and magmas in the Manyara-Balangida basin.
28
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Typhoons driven morphodynamics of the Wan-Tzu-Liao sand barrier
(Taïwan)
Lucie CAMPMAS1,4 , [email protected]
Frédéric BOUCHETTE1,4, Samuel MEULE2,4, Jying-Yih LIOU3
1
Montpellier II university, Géosciences-Montpellier CNRS, UMR 5243, 34095 Montpellier, France
Aix-Marseille university, CNRS IRD CEREGE, UM34, 13545 Aix en Provence, France
3
National Cheng Kung University, No.1, University Road, Tainan City 701, Taïwan
4
GLADYS / SO LTC, OSU OREME, CNRS / Montpellier II university, France
2
Keywords: Morphodynamic patterns, Monsoon/typhoons seasons, Shoreline changes
METHODOGY
In the framework of the KUNSHEN project, 7 months of monitoring (2011-2012) provided 20
topobathymetric surveys (within a 350 m long segment of the barrier from a water depth of ~
1.5 m below the lowest tide level to the back-barrier) and acquisitions of nearshore
hydrodynamics including velocity profiling and free surface measurement. Morphologic
changes were monitored using D-GPS each week during winter monsoon season and just before
and after each event during summer typhoon season. Offshore waves were extracted at Cigu
buoy (1,5 km off the coast in 18 m of water depth). Additionally, nearshore waves and water
level on the beach were acquired from the current profiler deployed 400 m off the coast in 4 m
of water depth and a network of pressure sensors deployed along a cross-section through the
barrier, respectively.
MORPHOLOGICAL CHANGES DRIVEN BY TYPHOON, A GROUP OF TYPHOONS
AND THE WHOLE SEASON
Amongst the eight studied typhoons, TALIM is the most energetic and representative event
observed of the seasonal pattern. Offshore wave height reached H1/3 = 10,34 m (Tp = 14,6 s) at
Cigu buoy and Hs = 2,3 m (Tp = 13,4 s) at the profiler. At the storm apex, the dune-top (3 m
above mean sea level) has been surged. Morphological changes included 6,7 m of dunefoot
retreat and a sand transfer from a dune breach to wash-over deposits in the lagoon. More
surprisingly, the foreshore was nourished (+3387 m3, +0,077 m above mean sea level in
average) as well as the whole sand barrier (+2345 m3). This sand input is interpreted as the
ultimate stage of the landward migration cycle of subtidal sandbars occurring throughout the
whole season driven by groups of typhoons. Although winter are erosive season (-4146 m3), the
summer results in an accretion period (+3431 m3) with a foreshore nourishment (+5667 m3,
+0,25 m above msl) and a shoreline seaward shift (10,4 m) (figure 1). Over the annual time
period, the sand barrier recorded 18,5 m of retreat concomitantly with a 11,1 m widening
without any significant abrasion of the dune-top or sand loss.
29
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Figure 1: a) Study area of Wan-Tzu-Liao sand barrier. b) Crosshore profile of the study area monitored from 2011-2012
with typology used. c) Wave and wind conditions from 2011 to 2012. Wave conditions are measured at Cigu buoy. Wind
conditions are measured at Cigu buoy until June 2012 and at the inland station from June to August 2012.
30
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
A new method for assessing spatial return levels of extreme waves
Romain Chailan1,2,3,4, [email protected]
Frédéric Bouchette1, Anne Laurent2, Gwladys Toulemonde3
Géosciences Montpellier – Université Montpellier 2 – 34095 Montpellier cedex
Lirmm – Université Montpellier 2 –34095 Montpellier cedex
3
I3M – Université Montpellier 2 –34095 Montpellier cedex
4
IBM France – Parc industriel de la Pompignane –34060 Montpellier cedex 2
1
2
Keywords: Extreme analysis, Max-stable processes, Wave-features hindcast
CONTEXT
In the analysis of coastal hazards, the features of extreme waves are determining information to
question the impact of storms to the coast. The spatial behaviour of extreme waves is even more
valuable especially since it is sparsely provided. Regarding recent applications in other contexts,
a kind of statistical models called max-stable processes is relevant for modelling spatial extreme
events. Max-stable processes are extensions of the well-known Generalized Extreme Value
(GEV) formalism. Unlike univariate approaches, max-stable processes consider spatial
dependence of a phenomenon. Such a modelling also overtakes a standard multivariate
approach by providing information continuously over the area studied, even where no
observation is available. Relying on such a stochastic modelling, the aim of this study is to
discuss the extreme waves hazard in the Gulf of Lions, focusing on their spatial behaviour.
METHOD
The storm-waves in the Gulf of Lions are well known for their abrupt changes. However, they
are only monitored i) by four surface buoys and ii) for a maximum period of a decade. We use
those data to perform a preliminary study on significant waves. Whether using univariate
(Fischer and Tippett, 1928) or bivariate (Resnick, 1987) modelling, a bias occurs while
extrapolating data from the stochastic model to obtain long return levels. The bias results from
the lack of long historical data set and hence the high sensitivity of the stochastic model
regarding the few extreme events recorded during that period. Regardless this drawback,
bivariate extreme value distributions on significant waves show a strong spatial dependence.
Thus we need to use a spatial approach as an alternative to fully integrate the dependence
between each observed site. One way is to use max-stable models (Smith, 1990; Schalther,
2002). Well-fitted max-stable models and therefore the quality of their extrapolations rely on the
availability of a representative data set, both in time and space. To pass over the scarcity of
observations, a strategy based on numerical simulation of the wave-features is much relevant
although it can introduce numerical approximations over the domain studied. Therefore we
build a wave hindcast for a fifty-one-year period (1961-2012) thanks to the third generation
wave model WaveWatchIII® in its most recent development (Tolman, 2014). Driven by
regional atmospheric and oceanic re-analyses, WaveWatchIII® performs a wave spectral
modelling on a refined unstructured grid. Several max-stable models are fitted to this reliable
data set. The best of those is selected to determine quantities of interest, showing that such a
31
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
combination of numerical wave modelling and stochastic modelling significantly enhances the
understanding of extreme waves behaviour (see simulation Figure 1).
Among these quantities, a mapping of extreme waves return levels is constructed. Joint
probabilities questioning -- e.g., the probability of having a significant-wave at both sites A and
B over their marginal 10-year return value -- are also introduced to demonstrate the benefits
from the use of spatial max-stable modelling against classical univariate approaches.
Legend: A simulated max-stable process (Schlather, 2002) of significant waves over the
Gulf of Lions. It is generated from a max-stable model, here fitted to academic data. Stars
are surface-buoy locations. The spatial extreme modelling formalism requires more sites and
long data time series to extrapolate such information. This is achieved through the 51-year
hindcast simulation.
32
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Fluid inclusions and volatile-rich minerals in nephelinite as tracers of
fluids beneath the NW African Craton (Saghro volcanic field, AntiAtlas, Morocco)
René CHAMBOREDON1, [email protected]
Fleurice Parat1, Marie-Christine Boiron2
1
2
UMR5243 – Géosciences Montpellier, UM2 – Place E. Bataillon, 34095 Montpellier cedex 5, France
UMR7359 – GeoRessources Nancy, BP 20023, 54501 Vandœuvre les Nancy cedex, France
Keywords: Volatiles, fluid, liquid, mantle, alkaline lava, nephelinite, fluid inclusion, Raman,
microthermometry, olivine, metasomatism.
Volatile-bearing minerals in intraplate alkaline lavas attest of the presence of fluid
and/or volatile-rich liquid in the mantle. Fluid/liquid may be derived from asthenospheric
plumes, metasomatized subcontinental lithosphere or subducted material, and are therefore key
elements to understand magma genesis and mantle dynamics. To address the question of the
origin and composition of deep fluid and/or volatile-rich liquid, we investigated whole-rock and
mineral geochemistry and fluid inclusions of mafic alkaline lavas from the Saghro volcanic field
(Morocco, NW African Craton).
The mafic lavas are nephelinites with phenocrysts of olivine (Fo90–82), clinopyroxene
(Mg# = 87–49), nepheline and volatile-rich minerals: phlogopite, apatite (F = 1.0–2.9 wt.%, Cl
= 0.11–0.26 wt.%, SO2 = 0.06–0.42 wt.%), pyrrhotite (NFeS = 0.90–0.98) and magnetite (Xulvö
= 0.19–0.21). The mineral assemblage and composition constrain the pre-eruptive conditions of
nephelinite at oxidized redox state (logfO2=NNO–NNO+1) and 1000-1100°C (cpx-melt
equilibria). Nephelinites are mafic alkaline silica-undersaturated lavas (Na2O+K2O = 2.1–6.2
wt.%, SiO2 = 37–43 wt.%, Mg# = 70–62). Their high Ca/Al (1.0–1.5) and Zr/Hf (44.2–55.9)
ratios, high concentration in incompatible elements and negative anomalies in K, Zr, Hf and Ti
suggest a carbonatite-metasomatised peridotite source.
Primary fluid inclusions are present in olivine (Fo90–85) as (i) isolated or trails of
translucent fluid inclusions; (ii) dark isolated inclusions with daughter minerals of nepheline ±
apatite, and (iii) multi-phased inclusions with fluid and daughter minerals of nepheline ± apatite
± magnesite ± phlogopite. Microthermometry and micro-Raman spectrometry study of
translucent inclusions indicates pure supercritical CO2. Assuming a temperature of 1100°C, the
trapping pressure for pure CO2 system is in the range 300–1050 MPa.
Our study indicates that fluid and/or volatile-rich silicate liquid (C-O-H-S-Cl-F) is
involved during the genesis and evolution of alkaline magma. Fluid-rock interaction may have
been an important process beneath the NW African craton, leading to metasomatised mantle
with CO2–rich carbonatitic components.
33
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Water content and hydrogen behavior during metasomatism in the
uppermost mantle beneath Ray Pic volcano (Massif Central, France)
Carole DENIS 1, [email protected]
Olivier ALARD1, Sylvie DEMOUCHY1
1
Geosciences Montpellier, University of Montpellier 2, place E. Bataillon, Montpellier, France
Keywords: Peridotite, water content, metasomatism, Massif Central
From experimental studies, we know that some of the Earth’s water can be stored as hydrogen
in point defects in the nominally anhydrous minerals (NAMs) of the Earth’s mantle. These
NAMs (e.g. olivine, pyroxenes and garnet) can contain up to hundreds of parts per million
hydrogen atoms. To assess this important deep water reservoir and the Earth deep water cycle,
water content must be quantified as well as the H behavior during mantle key processes such as
melting and metasomatism.
Nine xenoliths of spinel peridotite from the Ray Pic locality, in the southern part of the French
Massif Central (France) have been characterized by major, minor and trace elements
compositions including water contents were obtained by electron microprobe, laser ablationICPMS and FTIR, respectively.
The sample suite investigated is lherzolites equilibrated at relatively low temperatures
(900 < T ≤ 1050ºC, using Ca-in pyroxenes, [1]). All samples show recrystallized
microstructures varying between porphyroclastic, coarse granular and equigranular. Bulk major
element compositions, modal abundances, mineral compositions and equilibrium temperatures
are typical of the cold-uppermost part of the ‘fertile’ mantle lithosphere beneath the Ray-Pic
area [2; 3]. However, contrary to previous studies, 6 xenoliths out of 9 show pargasite, with
modal abundances varying from 0.2 up to 8.2%.
Cpx’s normalized REE patterns show a continuum between light REE depleted ((La/Sm) N≈ 0.3)
to L-REE enriched patterns ((La/Sm)N≈16) and a relatively flat M-REE to H-REE segments
((Sm/Yb)N= 0.91±0.26). With suggest two types of metasomatism (1) with L-REE enriched
patterns show also U and Th enrichments but HFSE negative anomalies, usually ascribed to the
percolation of volatile-rich small volume melts within the cold sub-continental lithosphere [3; 4;
5]. And (2) a steady enrichment from light to heavy REE ascribed to a metasomatism at higher
melt/rock ratio.
H2O contents for the nominally anhydrous mineral (NAMs: ol, opx, cpx) are within the common
range of other spinel peridotites; with the highest hydrogen concentration in cpx and the lowest
in olivine. No correlation between hydrogen concentrations and (La/Sm)PM was observed.
Further, there is no correlation between H2O content in NAMs and the occurrence and/or
abundance of amphibole. However, broad correlations between water content in minerals and
(Yb)PM in clinopyroxene were found, suggesting that the variability of H2O content in NAMs is
primarily due to melt depletion. Implications for hydrogen behavior and water contents during
key mantle processes will be further discussed.
34
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Regional variability of lithospheric mantle beneath the Middle Atlas.
Hicham EL MESSBAHI1, 2 , [email protected]
Jean-Louis Bodinier2, Alain Vauchez2, Jean-Marie Dautria2, Houssa Ouali1, and Carlos J.
Garrido3
1. Equipe Géomatériaux, Université Moulay Ismaïl, Faculté des Sciences, BP 11201, Zitoune, Meknès, Morocco
2. Géosciences Montpellier, Université de Montpellier 2, Cc 60, Place Eugène Bataillon, 34095 Montpellier
3. Instituto Andaluz de Ciencias de la Tierra (IACT), CSIC and UGR, Avenida de las Palmeras 4, 18100 Armilla,
Granada, Spain
The ‘tabular’ Middle Atlas, between Azrou and Timahdite, is an area where intra-plate
Cenozoic volcanism coincides with nearly 2000m uplifting of the undeformed Mesozoic cover
and the maximum of lithospheric thinning beneath continental Morocco. This region also
concentrates the principal mantle xenolith localities in Morocco. It is therefore a key area to
study the mechanisms of lithospheric thinning and constrain the component of mantle buoyancy
that is required to explain the Moroccan reliefs. Previous studies have focused on a single
locality - the Bou Ibalghatene maar, in the central part of the volcanic district. There, the mantle
xenoliths show extensive reactions with silicate and carbonate melts that led to the formation of
a range of lithologies characterized by substantial olivine, clinopyroxene or amphibole
enrichment, as well as incompatible trace element enrichment. However, a survey of mantle
xenoliths from nine localities distributed throughout the Azrou-Timahdite district indicates that
the reaction and metasomatic imprints are less pronounced or virtually absent in the other suites.
The Bou Ibalghatene suite could represent a restricted area of focused melt flow through the
lithosphere. The present study focuses on mantle xenoliths from the Tafraout maar, located
45km to the North-East of Bou Ibalghatene and distal to the main volcanic district. The maar is
situated on the NE-SW North Middle Atlas Fault, a major transpressive fault separating the
‘folded’ Middle Atlas, to the South-East, from the ‘tabular’ Middle Atlas, to the North-West.
The samples have been investigated for their mineralogy, microstructures, crystallographic
preferred orientation (EBSD-SEM), and bulk rock and mineral compositions (XRF, EPMA and
LA-ICP-MS). They differ from the Bou Ibalghatene mantle xenoliths by the presence of fine
grain samples (mylonites), the lack of hydrous metasomatic phases (amphibole and phlogopite),
somewhat lower equilibrium temperatures, a higher fertility degree, and less enriched trace
element compositions. Several samples show LREE-depleted clinopyroxene compositions that
have not been observed at Bou Ibalghatene. These results indicate significant variations of the
mechanisms and degree of lithosphere-asthenosphere interaction across the Azrou-Timahdite
plateau. The Tafraout xenoliths may represent distal and attenuated effects of a mantle
upwelling centered on the Bou Ibalghatene maar and bordered by the Middle Atlas Fault to the
South-East. The Tafraout suite also records incipient stages of the lithosphere-asthenosphere
interaction that were erased by subsequent melt/fluid processes beneathBou Ibalghatene.
35
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
36
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Positioning the peridotite massifs of north-eastern Algeria in the
geodynamic evolution of the Western Mediterranean: A geochemical
and geochronological study
Laure Fernandez1, [email protected]
Bosch, D. 1, Bruguier, O. 1, Hammor D. 2 , Monié, P. 1, Arnaud, N. 1, Caby., R 1
1
Géosciences Montpellier, UMR-CNRS 5243, Université de Montpellier 2, Place Eugène Bataillon, 34095
Montpellier, Cedex 05, France
2
Université Badji-Mokhtar, BP12, El-Hadjar, Annaba 23 000, Algeria
Keywords: Geodynamic, geochemistry, geoschronology, isotopy, Mediterranean area
The dismembered fragments of the Alpine belt recovered in various places around the
Mediteranean basin are witnesses of the collisional events between Africa and Eurasia and of
the opening of the western Mediterranean basins during the Cenozoic. In the eastern part of
North Algeria (figure 1), basic and ultrabasic rocks outcrop in the Edough massif, which belong
to the internal zone of the Magrebides. Preliminary works [Bosch & al., 2014] from this area
have proposed that both amphibolites from Kef Lakhal and metagabbros from Bou Maiza
correspond to components formed in a back-arc basin environment.
This study is focused on the petrology, geochemistry and geochronology of the mantle rocks
from Kef Lakhal (KL) and Sidi Mohamed (SM) areas in order to constrain their origin and age
and, thus to propose a suitable scenario for their evolution in time and space during the
Cenozoic. The peridotites show a wide range of Mg number, mainly between 82 and 89.6 with
lower values measured for the Kef Lakhal peridotites. The amphiboles from Kef Lakhal are
mostly magnesio-hornblende and pargasite. Garnets from amphibolites range from almandine to
grossular.
Amphibolites display MORB-type REE patterns evolving from slightly depleted to enriched
patterns (0.5<La/SmN<2, 0.6<La/Yb<3). Peridotites present flat CHUR-normalized REE
profiles with a marked negative Eu anomaly for KL samples. The Nd and Hf isotopes for both
amphibolites and peridotites can be separated into two distinct batches. A first group shows a
typical DMM signature for Nd and Hf isotopes with Sr isotopic ratios more or less modified by
seawater impact. A second group yields significantly lower Nd and Hf isotopic values (down to
0.512200 and 0.28207, respectively) combined with higher Sr isotopic ratios (up to 0.7147).
These values suggest participation of an enriched component similar to detrital sediments,
which is also supported by Pb isotopes.
The Ar-Ar and U-Pb ages (in progress) will help decipher the evolution of these different
components and appear as essential in order to replace the NE algerian massifs in the
geodynamical evolution of the western Mediterranean during the Cenozoic.
37
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Figure 1: Geological map and localisation of Edough (Algeria), modified after Caby et al., 2001.
Bibliography
Bosch, D., Hammor, D., Mechati, M., Fernandez, L., Bruguier, O., Caby, R., & Verdoux, P.
(2014). Geochemical study (major, trace elements and Pb–Sr–Nd isotopes) of mantle material
obducted onto the North African margin (Edough Massif, North Eastern Algeria): Tethys
fragments or lost remnants of the Liguro–Provençal basin?. Tectonophysics.
Caby, R, D Hammor, and C Delor. “Metamorphic Evolution, Partial Melting and Miocene
Exhumation of Lower Crust in the Edough Metamorphic Core Complex, West Mediterranean
Orogen, Eastern Algeria.” Tectonophysics 342, no. 3–4 (December 2001): 239–273.
doi:10.1016/S0040-1951(01)00166-4.
38
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Surveillance et modélisation du stockage de l'eau en zone karstique
(Larzac, France) avec un gravimètre supraconducteur.
Benjamin FORES1, [email protected]
Cédric Champollion1, Nicolas Le Moigne1, Jean Chéry1
1
Géosciences Montpellier, UMR 5243, Université Montpellier II, France
Mots clés : Gravimétrie, Supraconducteur, Karst, Modélisation hydrologique
Réussir à quantifier le stockage et le transfert de l'eau souterraine en domaine karstique est
crucial pour la gestion et la protection des ressources en eau. Étant donné la très forte
hétérogénéité des propriétés hydrogéologiques des karsts, les observations géophysiques telles
que le suivi temporel de la gravité pourraient être utiles pour combler le vide entre les études à
l'échelle locale (basées sur des forages, capteurs d'humidité...) et l'échelle globale (chimie, débit
des rivières...).
Depuis plus de deux ans, l' igrav#002, un gravimètre supraconducteur de nouvelle génération,
mesure en continu dans l'observatoire ''GEK'' : Géodésie en Environnement Karstique, sur le
plateau du Larzac, dans le sud de la France. L'observatoire est situé sur plus de 250 m de
dolomite karstifiée, avec une zone non saturée d'environ 150 mètres. Dans cette étude, nous
présenterons d'abord une évaluation des données du gravimètre supraconducteur (calibration,
dérive, corrections). Ensuite, une analyse détaillée des effets globaux, des effets topographiques
et du bâtiment sera faite afin d'estimer le stock d'eau uniquement. Enfin, un premier modèle
hydrologique simple sera présenté pour débuter l'interprétation de l'hydrologie karstique de la
zone.
39
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
a)
b)
Légende : a) l'observatoire GEK sur le Larzac ; b) l'igrav dans la chambre centrale isolée du GEK ; c) comparaison
entre les données de l'igrav et les données hydrologiques classiques (pluviométrie / débit de la source)
40
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Could Erosion in the Western Alps triggers large earthquakes in the
Ligurian basin?
Genti M. 1, [email protected]
Chéry J. 1, Vernant P. 1, Larroque C. 2
1
2
Géosciences Montpellier, CNRS-UM2, Place E. Bataillon, 34095 Montpellier, France
Géosciences Azur, UMR 6526 CNRS-UNS, 250 av. Einstein, 06560 Valbonne, France
Keywords: Ligurian basin, 2D thermo-mechanical modelling, erosion, seismicity, isostatic
rebound.
Earthquakes express present-day deformation at the Alps-Ligurian basin junction.
Convergence rates across the Western Alps are below the uncertainty threshold of the
continuous GPS measurements (< 0.3 mm/yr), but unexpectedly, the vertical rates derived
from the GPS are significant and up to 2 mm/yr. Furthermore, the range is underlined by
moderate but frequent instrumental seismicity. Focal mechanisms show extension in regions
of moderate to high elevations with a direction normal to the Western Alps range axis, while
their foreland is associated to strike slip and thrust faulting. How can be explained these very
high uplift rates and seismotectonic regime in an intraplate like kinematic deformation pattern
remains an open question.
Recent 2D finite element models have tried to answer to this question by showing that erosion
of mountain topography in low convergent zones induces a significant deformation of the
lithosphere. These models suggest two distinct seismotectonic zones characterized by
extension and uplift below the moderate to high topographic mountain range and shortening
in foreland. However, these models where not applied to a specific case study.
The last deadly earthquake was in 1887, in Ligurian Basin, with an estimated magnitude of
Mw=6,7. Many hypotheses are suggested to explain this active deformation. Using a 2D
cross-section of the Alpine-Ligurian margin, we study the effects of the processes surface
impact on the deformation pattern of the Ligurian Basin, and the possible triggering of
earthquake like the 1887 one.
41
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
0.7
8
0.6
erosion
7.5
7
6.5
6
5.5
5
4.5
0.5
0.4
0.3
0.2
0.1
0.0
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
sedimentation
Figure 4 Sedimentation rate influence the slip rate of a 75° north dipping plane fault (friction = 0.02) emerging at the
margin foot.
42
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Non – fickian solute transport in heterogeneous medium
Filip GJETVAJ1 , [email protected]
Philippe Gouze1
1
UM2, Géosciences Montpellier Place Eugène Bataillon, 34095 Montpellier, France
Keywords: Transport, Non-Fickian, Dispersion, Solute, Experiment
Solute transport managed by fluid flow in heterogeneous media has important role when
we want to ensure safe disposal of nuclear waste, access to clean drinking water or to have
control on any other process that includes contaminant transport in aquifers. Classical solute
transport theory developed in 1950s describes solute cloud spreading due to influence of
molecular diffusion and kinematic dispersion. Kinematic dispersion is a mixing phenomenon
that on a pore scale occur due to different path lengths, velocity profile in each pore and
velocity differences between pores. This processes are described by (Fickian) advectiondispersion equation (ADE), but experiments both in situ and in laboratory shows that ADE
fails to predict true behavior of solute transport.
Breakthrough curves (BTCs) obtained by experiment are strongly asymmetrical with long
recovery times. Although concentration in late times has several orders of magnitude lower
value comparing to a peak concentration this tail cannot be neglected. Such behavior is result
of heterogeneities that exists even in most homogeneous structures. Even thought
theoretically if there is large enough homogeneous media, the transport will become Fickian
this is not realistic option for any real aquifer because heterogeneities exists on multiple scales
and they all affect solute transport.
In last twenty years due to technical development it has been recognized that matrix diffusion
is very important transport mechanism. Matrix diffusion is process where solute diffuses
between regions of flowing water and stagnant regions. This effect occur due to concentration
differences between two zones. Solute is transported by flow through mobile zone and
diffuses to stagnant zone. After the peak concentration has passed “clean” water enters mobile
zone and reverse process occur. Now concentration in stagnant zone is larger than in mobile
and solute diffuses back, this process is relatively slow comparing to advection because it is
dominated by diffusion with small concentration gradients. Tailing of BTCs is as well caused
by heterogeneities and it can be difficult to distinguish influences of these two processes.
It is necessary to develop tools that will allow to predict and quantify influence of matrix
diffusion and media heterogeneities to BTCs tailing. This can be achieved by performing
laboratory experiments on porous media with different properties (heterogeneities and
mobile/immobile zone ratio). 3D images of such pore space will give base to perform
numerical simulation of transport and determine coefficients. The same way of determination
coefficient will be used for other samples and results from numerical simulation will be
compared with experiment data in order to validate procedure.
43
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Fig. 1
BTC showing tracer experiment with uranine (non reactive tracer), Fickian (ADE) and non-Fickian model
on same data set
44
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Déformation Holocène de l’Himalaya du Bhoutan, apport de la
géomorphologie et de la paléosismologie
Romain LE ROUX-MALLOUF1, [email protected]
Rodolphe CATTIN1, Matthieu FERRY1, Jean-François RITZ1, Vincent GODARD2
1
2
Laboratoire Géosciences Montpellier - Université Montpellier 2 – 34090 Place Eugène Bataillon
CEREGE – Aix-en-Provence – 13545, Aix en Provence cedex 4
Mots clés : Tectonique active, cycle sismique, paléosismologie, modélisation numérique
La chaine himalayenne est une des régions à la surface de notre planète où les processus
climatiques et tectoniques sont les plus intenses. De nombreuses études menées depuis plus de
30 ans ont permis de documenter la déformation et les séismes majeurs associés de cette
région (M>8) (Chen & Molnar 1977; Schelling & Arita, 1991 ; Lavé & Avouac, 2000).
Bien qu’étant une zone clé pour l’étude des variations latérales le long de l’arc Himalayen, les
premières études de la déformation quaternaire au Bhoutan sont très récentes. Ainsi, Berthet
et al. 2014, à travers une analyse morphotectonique de la partie centrale du Bhoutan, montre
l'existence d'une déformation holocène équivalente à celle observée au Népal (deux séismes
majeurs (M>8) durant les derniers 1100 ans).
Nous proposons ici, d'affiner ces observations préliminaires, en quantifiant plus en détail cette
déformation. Les liens entre les procesus de dénudation et les processus tectonique
(mécanismes et géométries) sont abordés par une analyse des concentrations en 10Be des
sédiments de rivière, le long d'un transect latitudinal dense.
Une première analyse morphotectonique et paléosismologique détaillée de deux sites au front
a également été effectuée lors d'une première mission de terrain.
Le taux de soulèvement vertical ainsi obtenu, couplé à la géométrie des structures en surface,
puis en profondeur devrait aboutir à termes à l'estimation d'un taux de raccourcissement
horizontal qui sera comparé aux données GPS.
45
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
46
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Present-day strain partitioning and strain transfer across the
Fairweather and Denali Faults in SW Yukon – SE Alaska
Anaïs MARECHAL, [email protected]
Stéphane Mazzotti1, Jean-François Ritz1, Matthieu Ferry1
1
Géosciences Montpellier, Université Montpellier 2, Place E. Bataillon, 34 095 Montpellier
Keywords: partition, deformation, GPS, géomorphologie, modélisation
In SW Yukon – SE Alaska, the present-day Pacific – North America relative motion (~55
mm/yr) is highly oblique to the main plate boundary, resulting in strong strain-partitioning
tectonics that link the Aleutian subduction to the west to Queen Charlotte transform to the
south. This transition region is also the site of present-day orogeny (St Elias) and accretion of
the allochthonous Yakutat Terrane to the Northern Cordillera.
Multiple datasets (GPS, geomorphology, seismicity) are integrated to characterize and
quantify strain patterns in this transpressional system, with particular emphasis on strain
partitioning between strike-slip and shortening deformation. New campaign and permanent
GPS stations straddling the main faults (Denali, Fairweather: vertical lithospheric scale faults)
indicate that that 95% of the Pacific-North America strike-slip motion is accommodated on
the main plate-boundary Fairweather Fault, leaving near-zero motion on the Denali Fault only
~100 km inboard. In contrast, the fault-perpendicular component is strongly distributed
between shortening offshore and in the orogen, and 25% of the convergence transferred
inland. This latter strain transfer could explain the seismicity observed in the Mackenzie
Mountains 500 – 800 km from the coast.
In the region of highest convergence obliquity, GPS data show a diffuse indentor-like
deformation, with strong along-strike variations of the main fault slip rates. Preliminary
results of a regional geomorphology study give further information about the Denali fault,
along which previous data indicate a velocity decrease from 8 mm/yr (Matmon et al.,2006) to
4 mm/yr (Seitz et al., 2010) over 200 km along strike. A high resolution DEM (2m) processed
from Pleiades data acquired in September 2013 highlights a significant vertical component on
the Denali fault. Systematic metric scale displacements are measured along the “inactive” part
of the fault, showing recent deformation since the Last Glacial Maximum in the region (~20
kyrs ago). Sampling of geomorphological markers for Be10 and OSL datation is planned in the
summer 2014 in order to estimate slip rates along the southern part of the main transpressional
faults (Denali, Totschunda).
47
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Figure 5: Schematic map of the indentor model and velocity results
48
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Déformations extrêmement lentes et mouvement verticaux : apport du
GPS et du nivellement pour contraindre des modèles numériques
NGUYEN Hai Ninh1,2,3
Philippe Vernant1
Stéphane Mazzotti1
1
Géosciences Montpellier (France) ; 2 TOTAL E&P, Stavanger (Norway) ; 3 TOTAL SA, Pau (France)
Mots clés : Western Alpine, Pyrénées, GPS, déformation, mouvement, convergence
Les chaines de montagnes françaises sont caractérisées par une sismicité modérée et
une déformation horizontale qui ne peut pas pour l’instant être mise en évidence par
les mesures GPS. Seule la borne supérieure des conditions aux limites de ces chaines
peut être donné (±0.5 mm/an, ex. : Nocquet et Calais, 2003, 2004, Vernant, résultats
non publiés). Pourtant avec un séisme de magnitude 5 environ tous les 8 à 10 ans et
un de magnitude 6 tous les 150200 ans dans les Pyrénées (Souriau & Pauchet, 1998),
il semble évident que cette chaine se déforme encore de manière active, même si c’est
de manière très lente. Des résultats préliminaires de modélisation numérique
indiquent que cette déformation pourrait être due simplement à l’érosion. Dans ce cas
les vitesses verticales pourraient être bien supérieures aux vitesses horizontales. La
France est couverte par un réseau GNSS permanent (RGP), et des données sont
disponibles pour les pays limitrophes (Espagne, Italie, Suisse). L’objectif de la thèse
sera multiple :
- Traiter toutes les données du RGP pour identifier les sites stables analyser
précisément les séries temporelles des sites stables pour déterminer leur vitesse
verticale
- Retraiter les campagnes de nivellement disponibles pour la chaine des Pyrénées
- Développer des modèles numériques 3D de la déformation des Alpes et Pyrénées en
tenant compte de l’érosion
L’objectif de cette thèse est donc de mieux comprendre les mécanismes de
déformation des orogènes identifiés comme inactifs au sens des vitesses de
convergence aux limites et de préciser si l’on peut encore utiliser le paradigme de
l’effondrement gravitaire pour expliquer la phase terminale de démantèlement des
orogènes.
49
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Figure 1. Distribution of the permanent GNSS stations used in
this study. Stars show the International GNSS stations of the
IGS Network. Squares show the GNSS stations of the European
Network (EUREF-EPN). Circles show the GNSS stations of the
French permanent GNSS Network (RGP and RENAG
Network). Symbols are colored based on the length of the data
span for each station.
Fig. 10a, b RMS of convergent time of velocity(a) and 1 uncertainty(b) for North, East, Up and 2D component with respect to 7 different
convergent thresholds (1.0, 0.8, 06, 0.5, 0.4, 0.2 and 0.1 mm/yr) for all stations. Forward time solution is F-dashed line, Backward time
solution is B-dash-doted line and synthetic time solution is Solid Line. The blue, green, red and violet represent North, East, Up and 2D
component, respectively. The y axis is in mm/year and the x axis is convergent time span in decimal year .
Fig. 11a, b. Horizontal (a) and vertical (b) velocities (in mm/yr) in the Western Alps and the Pyrenees region. The horizontal
velocities and their 95% confidence ellipses are given with respect to the stable Eurasian plate described in this study. The vertical
velocities and their 1- uncertainty are in ITRF2008 reference frame. Blue arrows: horizontal velocities of GPS stations that
observed for more than 4.43 years; Red arrows: vertical velocities of GPS stations that observed for more than 4.78 years.
50
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Imagerie de l’anisotropie sismique de la croûte – Exemple de la faille de
Denali : localisation de la déformation en profondeur à l’échelle
lithosphérique.
Nathalie RASENDRA1, [email protected]
Christel Tiberi1, Stéphane Mazzotti1
Géosciences Montpellier UMR 5243 - CC 60 Université Montpellier 2 Place E. Bataillon 34095
Montpellier cedex 5
1
Mots clés : Anisotropie sismique, tomographie, corrélations, bruit ambiant, faille de Denali.
La faille de Denali est un décrochement intracontinental dextre s’étendant sur plusieurs
milliers de kilomètres. Elle accommode une partie de la convergence entre la plaque Pacifique
et la plaque Nord-Amérique. La déformation en surface y est distribuée tandis que sa structure
en profondeur est encore méconnue : imager l’anisotropie sismique pourrait contribuer à
comprendre son rôle dans la distribution de la déformation en surface et en profondeur à
l’échelle lithosphérique.
L’analyse des fonctions récepteur a mis en évidence une anisotropie sismique localisée dans
la croûte moyenne et dont la direction de polarisation rapide est parallèle à l’orientation de la
faille. D’ailleurs, cette direction est cohérente avec celle obtenue grâce aux mesures SKS.
Les contraintes sur la caractérisation de cette anisotropie marquée sont encore insuffisantes.
Nous avons donc décidé de coupler les résultats issus des fonctions récepteur avec un autre
outil d’imagerie sismique : la tomographie par corrélations de bruit ambiant. Cette technique
se base sur l’enregistrement continu du bruit ambiant de la Terre présent partout ce qui permet
de s’affranchir de l’occurrence des séismes.
51
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Légende : a) Topographie (du modèle 1 minute d’arc ETOPO1) et schéma géodynamique de
la région d’étude. Les triangles indiquent la localisation des stations sismiques utilisées pour
l’étude. Les principaux systèmes de failles sont en traits pleins (Rasendra and al., 2014
accepted).
b) Variations azimutales des fonctions récepteur sur les composantes radiale et transverse de
la station BVCY.
52
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Realistic simulation of instantaneous nearshore water levels during
typhoons
Fabien Rétif 1 , Frédéric Bouchette 1 , Jiing-Yih Liou 2 , Samuel Meulé 3 , Héloïse Michaud 4 ,
Li-Ching Lin 5 , Kao-Shu Hwang 2 , Nans Bujan 2 , Hwung-Hweng Hwung 6 and the
SIROCCO Team 7
1. Géosciences-M, UMR 5243, University Montpellier 2 & CNRS, 34095 Montpellier, France
2. Tainan Hydraulics Laboratory, National Cheng Kung University, Taiwan
3. Aix-Marseille Université, CNRS, IRD, CEREGE UM34, Aix en Provence, France
4. SHOM, 42 avenue Gaspar Coriolis, 31157 Toulouse Cedex, France
5. International Wave Dynamics Research Center, National Cheng Kung University, Taiwan
6. Department of Hydraulic and Ocean Engineering, National Cheng Kung University, Taiwan
7. Laboratoire d’Aérologie – CNRS & University of Toulouse, 14, Avenue Edouard Belin, 31400 Toulouse,
France
Mots clés: instantaneous water level, wind, wave, current, typhoon, extreme phenomena
3D hydrodynamics simulations were performed on an area covering 600 km around the
Taiwan island (figure 1A) for the period running from September to October 2011. These
simulations discuss the regional hydrodynamic mechanisms which control the sea surface
elevation along the Wan-Tzu-Liao sand barrier (south-west Taiwan).
METHODOLOGY
The simulation is based on SYMPHONIE (Marsaleix et al., 2008), a robust 3D circulation
model dealing with most of the oceanographical forcings (winds, air/sea fluxes), global scale
circulation (tides, Kuroshio current), rivers and waves. In the framework of the KUNSHEN
project (ANR/NSC), a raft of devices were set in front of the Wan-Tzu Liao barrier during 7
months of monitoring including the simulated period. The equipments were deployed along a
cross-shore section (in 18 m, 7 m, 4 m of water depth and on the emerged beach) and
provided robust informations on nearshore hydrodynamics and water levels. We confront
these measurements to the simulated instantaneous water levels, surface and bottom current
velocities to validate the model with a particular emphasis on water level to the shoreline.
RESULTS
The figure 1B shows the sea surface elevation (at the 18m buoy) controlled by tide (harmonic
reanalysis from FES2012), global currents (MERCATOR) and atmospheric conditions
(ECMWF). The maximal elevation generated by the tide is 77 cm. For global currents, the
mean elevation is 70 cm and the maximal is 84 cm. Regarding the atmospheric forcings, the
maximal elevation is 19 cm and the mean elevation is 10 cm. We show that tides and global
currents control mainly the sea surface elevation; but for the analysis of the submersion, it is
also important to take into account the effect of atmospheric conditions. Regardless the wave
effect, the simulation reproduces correctly the measures with a quality equivalent to that
observed in Michaud et al, (2012) in the Gulf of Lions (France).
53
Journée Des Doctorants Géosciences Montpellier – 10 juin 2014
Figure 1 – A) The polar grid with a nearshore resolution of 460 m and 5.6 km at the offshore,
and the typhoon tracks during the considered period; B) analysis of the sea surface elevation
according to the forcings at the 18 m buoy of water depth.
REFERENCES
Marsaleix P., Auclair F., Floor J. W., Herrmann M. J., Estournel C., Pairaud I. and Ulses C.
(2008):Energy conservation issues in sigma-coordinate free-surface ocean models, Ocean
Modelling, Vol. 20, pp. 61–89.
Michaud H., Marsaleix P., Leredde Y., Estournel C., Bourrin F., Lyard F., Mayet C., Ardhuin
F. (2012): Three-dimensional modelling of wave-induced current from the surf zone to the
inner shelf, Ocean Science, Vol. 8, pp. 657-681.
54

Ouvrir - CHU Montpellier

Liste des candidats - Elections Universitaires 2014

FORMATION EXPÉRIENCE

le programme. - CHU Montpellier

cartels gare - Herault Transport

CV (document PDF) - Nicolas Claveau

Invitation

CV Vincent TECHER 2

Profession de foi - Elections Universitaires 2014

Perfectionnement en IRM