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PhD Position in the “Volcanoes” Team of
Laboratoire de Géophysique Interne et Tectonophysique-Chambéry, France
From:
Philippe Lesage <lesage@xxxxxxxxxxxxxx>
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Magma-crust mechanical interactions modeling: Application to storage
zones and andesitic volcanic conduits.
In physical volcanology, it is necessary to develop new models in order
to benefit from the increasing quality of geodetic and seismic
measurements (Sparks et al., 2003; Poland et al., 2006). New models have
improved our knowledge of storage zones geometry or crustal rheology.
But in order to obtain predictive information on the ongoing eruptive
history it is crucial to correctly take account of the coupling between
magma (Newtonian fluid with gas) and the surrounding crust, which
behaves as an elastic solid on the time-scale of an eruptive cycle. This
PhD will focus on this aspect trying two answer two key questions:
- How a modification of the stress field condition (resulting from
surface load variations or seismic events… ) may act on the storage? Any
given stress field change around a magma chamber affects the magma
pressure, which may in turn lead to changes of gas content and induces
surface deformation (Voight et al., 2006). Such a stress field variation
also induces changes of the threshold pressure above which an eruption
may start. 3D numerical models will be performed based on previous 2D
analytical results (Pinel et al., 2005). This study will be applied to
Icelandic sub-glacial volcanoes for which seismic and deformation data
(Pinel et al., 2007) are available inside the European Project VOLUME
(http://www.volume-project.net) (2005-2008).
- Which constraints can bring seismic and deformation data on the
conduit flow conditions? Correlation between deformation, seismicity
rate and eruptive activity has been shown at Soufriere Hills volcano
(Voight et al, 1998). Fluid mechanics models are developed to understand
modification of magma physical properties which could explain variations
of eruptive activity (Melnik et al., 2005). Despite recent progress
(Neuberg et al., 2006), the link between these models and deformation or
seismicity induced is not completely done yet. We will work on this
subject with an application to Mexican volcanoes (Colima, Popocatepetl)
for which data are available through our collaboration with the
Universidad Nacional Autonoma de Mexico (Extension of European project
VOLUME, Memorandum of Understanding between LGIT and UNAM). Numerical
modeling of fluid flow will be carried out with Hélène Massol (UMR 8148
CNRS-Université de Paris-Sud).
A solid background in geophysics and an interest for numerical modeling
is required.
Start date: September 2007,
Application before 1st June 2007.
Contact: Philippe Lesage (Philippe.Lesage@xxxxxxxxxxxxxx), Virginie
Pinel (Virginie.Pinel@xxxxxxxxxxxxxx), (33) 4 79 75 86 51.
Melnik, O., Sparks, R. S. J., Control on conduit magma flow dynamics
during lava dome building eruptions , 2005, J. Geophys. Res.,110,
doi:10.1029/2004JB003183.
Neuberg, J. et al., 2006. The trigger mechanism of low-frequency
earthquakes on Montserrat. J. Volcanol. Geotherm. Res., 153: 37-50.
Pinel, V. , Jaupart, C., Some consequences of volcanic edifice
destruction for eruption conditions, 2005, J. Volcnol. Geotherm.. Res.,
145, 68-80, doi:10.1016/j.jvolgeores.2005.01.012.
Pinel, V., Sigmundsson, F., Sturkell, E., Geirsson, H., Einarsson, P.,
Gudmundsson, M. T., Hognadottir, T., Discriminating volcano deformation
due to magma movements and variable surface loads: Application to Katla
subglacial volcano, Iceland, 2007, Geophys. . J. Int., sous-presse.
Poland, M. and Hamburger, M. and Newman, A., The changing shapes of
active volcanoes: History, evolution and future challenges for volcano
geodesy, 2006, J. of Volcanol. Geoth. Res., 150,1-13,
doi:10.1016/j.jvolgeores.2005.11.005.
Sparks, S. R. J. , Forecasting volcanic eruptions, 2003, Earth Planet.
Sci. Lett, 210, 1-15
Voight, B., Hoblitt, R. P. ,Clarke, A. B. ,Lockhart, A. B., Miller, A.
D., Lynch, L., Remarkable cyclic ground deformation monitored in
real-time on Montserrat, and its use in eruption forecasting, 1998,
Geophys. Res. Lett., 25, 3,405-3,408.
Voight, B.; Linde, A. T.; Sacks, I. S.; Mattioli, G. S.; Sparks, R. S.
J.; Elsworth, D.; Hidayat, D.; Malin, P. E.; Shalev, E.; Widiwijayanti,
C. Young, S. R.; Bass, V.; Clarke, A.; Dunkley, P.; Johnston, W.;
McWhorter, N.; Neuberg, J.; Williams, P., 2006. Unprecedented pressure
increase in deep magma reservoir triggered by lava-dome collapse,
Geophys. Res. Lett., Vol. 33, No. 3, L03312
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