EGU2020-11571
https://doi.org/10.5194/egusphere-egu2020-11571
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Piton de la Fournaise, elasto-plastic models of stresses and deformation accounting for the topographic load and a magmatic injection

Muriel Gerbault1, Fabrice Fontaine2, Aline Peltier2, Lydie Gailler3, Riad Hassani4, Jean-Luc Got5, and Valerie Ferrazzini2
Muriel Gerbault et al.
  • 1IRD, GET, Toulouse, France (muriel.gerbault@get.omp.eu)
  • 2Observatoire Volcanologique du Piton de la Fournaise, IPGP, La Réunion, France
  • 3CLERVOLC, UCA, Clermont-Ferrand, France (lydie.gailler@uca.fr)
  • 4Geoazur, UNSA, Valbonne, France (riad.hassani@unice.fr)
  • 5ISTERRE, Université de Savoie, Chambery, France (Jean-Luc.Got@univ-smb.fr)

Building on previous work aimed at identifying and characterizing the potential mechanical trigger controlling eruptions and destabilization at Piton de la Fournaise, we study the mechanical behavior of the volcanic edifice on a crustal scale. Do the recurrent earthquake pattern correspond to a destabilization structure, precursor of a large-scale flank sliding? Or instead to a reactivated area of magma storage (partially crystallized “sill”)? To answer these questions, we design numerical models which estimate the stress field associated with the volcanic complex. We use the ADELI finite element method in three dimensions, which handles elasto-visco-plastic rheologies. In these models, we take into account 1) the topographic load, 2) the major density and resistance heterogeneities within the volcano obtained from previous studies, and 3) the overpressure induced by the intrusion of a dike of arbitrary geometry.
The model
ed dike injection generates deformation and stress fields such that their isocontours highlight an ellipsoidal cup structure extending from the central cone to a depth close to 0 and reaching the ends of the eastern flank. This zone could be assimilated to the zone of seismicity observed and described previously. Together with several systematic test cases, we will discuss the significance of these results, such as whether it reveals a rheological delimitation zone of the hydrothermalized bedrock, resulting from the combined influence of the topographic load and that of a magmatic injection.

How to cite: Gerbault, M., Fontaine, F., Peltier, A., Gailler, L., Hassani, R., Got, J.-L., and Ferrazzini, V.: Piton de la Fournaise, elasto-plastic models of stresses and deformation accounting for the topographic load and a magmatic injection, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11571, https://doi.org/10.5194/egusphere-egu2020-11571, 2020

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Presentation version 1 – uploaded on 02 May 2020
  • CC1: Questions and answers from the live chat during EGU2020, Michael Heap, 11 May 2020

    Q: How about multiple injection events? Did you consider and model the possible cumulated effect?

    A: See Camila might better answer, but given the signal, i'm not sure multiple injections were discernable

    Q: Are the values required to explain the observed deformation with a purely elastic model unrealistic?

    A: Pure elasticity fit the spatial pattern but not the timing, unless a scenario like LeMevel et al.

    Q: Any change in deformation observed after the M8.8 Maule event?

    A: There is no change in the uplift trend during the earthquake of 2010

    Q: What type of viscoelasticity did you use? As this can strongly influence the temporal deformation pattern...

    A: We use Maxwell viscoelasticity. Because modeling was made to fit the dataset, the aim was only to provide average viscosity property within the prefound shell geometry, therefore simple linear maxwell elastoviscosity

    Q: Could gravity data be used for Laguna del Maule?

    A: Yes, there is data, ref. in slide 1 in small: used to think of the shell reservoir and partially molten properties as reasonable for the viscosity obtained, 10¹⁷Pa.s

    Q: How did you decide the geometry of the VE mush, and how do you tackle non-uniqueness?

    A: We made an inversion to find the shape that best fit the surface pattern of displacemnts. To complement Camila's answer, in the paper are the details about non-uniqueness solutions.