Insights into the magma transport beneath active volcanoes from seismic and geodetic networks

• Main Author: Journeau, Cyril
• Other Authors: Institut des Sciences de la Terre (ISTerre), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)-Université Gustave Eiffel-Université Grenoble Alpes (UGA), Université Grenoble Alpes 2020-., Nikolai M. Shapiro, Aline Peltier
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: HAL CCSD 2022
• Subjects: Magma transport; Network-Based methods; Volcano seismology; Volcano deformation; Piton de la Fournaise volcano; Klyuchevskoy Volcanic Group; Transport du magma; Méthodes de réseaux; Sismologie volcanique; Déformation des volcans; Piton de la Fournaise; Groupe volcanique du Klyuchevskoy; [SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology; Kamchatka
• Online Access: https://theses.hal.science/tel-03925423; https://theses.hal.science/tel-03925423/document; https://theses.hal.science/tel-03925423/file/JOURNEAU_2022_archivage.pdf

The occurrence and style of volcanic eruptions are largely controlled by the mechanisms ofmagma storage and transport from the deep roots of the system to the surface. This functioning often remains misunderstood, in particular for the deep part.In this thesis, we use geophysical measurements from seismic and GNSS networks to constrain the sources activated before and during the eruptions of Piton de la Fournaise (La Réunion, France) and the Klyuchevskoy Volcanic Group (Kamchatka, Russia).The dense networks of instruments present in these two contexts and their strong volcanic activity make them ideal natural laboratories for testing new sophisticated methods aimed atexploring and extracting information on magma transport.We thus applied seismic network methods to analyze in detail the large seismic tremor database associated with the 23 eruptions of Piton de la Fournaise that took place in the 2014-2022 time period. The mechanism of generation of this tremor is directly linked to the shallow magma degassing close to the eruptive sites. The monitoring of its different properties (frequency, amplitude, state) and the comparison with other observables available at the OVPF-IPGP allows a better constraint of the eruptive dynamics of the Piton de la Fournaise dominated by the interactions between the magma liquid and gas phases.The analysis of continuous data from the GNSS network at Piton de la Fournaise allowedus to image the pressure sources active in its deep and shallow system. We also performeda comparison of these pressure sources with the associated seismicity for the pre-eruptive and co-eruptive periods.At the Klyuchevskoy Volcanic Group, the analysis of the tremor over the 2015-2016 timeperiod reveals a wide spatial distribution of its sources spanning the entire crust and connecting different volcanoes of the group. Tremor activity is characterized by rapid vertical and lateral migrations explained by fast pressure transients and dynamic permeability L’occurrence et le style des éruptions volcaniques ...