Sujet
rift zones, ring-faults, stress transfer, basaltic volcanism, calderas, [SDU.STU.VO]Sciences of the Universe [physics]/Earth Sciences/Volcanology

Domaines
Géologie, Sciences de la Terre, Géophysique

Description

International audience Surface deformation accompanying dike intrusions is dominated by uplift and horizontal motion directly related to the intrusions. In some cases, it includes subsidence due to associated magma reservoir deflation. When reservoir deflation is large enough, it can form, or reactivate pre-existing, caldera ring-faults. Ring-fault reactivation, however, is rarely observed during moderate-sized eruptions. On February 21st, 2015 at Ambrym volcano in Vanuatu, a basaltic dike intrusion produced more than 1 meter of co-eruptive uplift, as measured by InSAR, SAR correlation, and Multiple Aperture Interferometry (MAI). Here we show that an average of ∼40 cm of slip occurred on a normal caldera ring-fault during this moderate-sized (VEI < 3) event, which intruded a volume of ∼24 million cubic meters and erupted ∼9.3 million cubic meters of lava (DRE). Using the 3D Mixed Boundary Element Method, we explore the stress change imposed by the opening dike and the depressurizing reservoir on a passive, frictionless fault. Normal fault slip is promoted when stress is transferred from a depressurizing reservoir beneath one of Ambrym’s main craters. After estimating magma compressibility, we provide an upper-bound on the critical fraction (f = 7%) of magma extracted from the reservoir to trigger fault slip. We infer that broad basaltic calderas may form in part by hundreds of subsidence episodes no greater than a few meters, as a result of magma extraction from the reservoir during moderate- sized dike intrusions.

Mots-clés

Langue
English (en-GB)

Auteurs
Shreve, Tara, Grandin, R., Smittarello, D., Cayol, Valérie, Pinel, V., Boichu, M., Morishita, Y.

Contributeurs
Institut de Physique du Globe de Paris (IPGP) ; Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Institut des Sciences de la Terre (ISTerre) ; Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-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), Laboratoire Magmas et Volcans (LMV) ; Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Recherche pour le Développement et la société-Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne (UCA)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC) ; Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne (UCA), Laboratoire d’Optique Atmosphérique - UMR 8518 (LOA) ; Institut national des sciences de l'Univers (INSU - CNRS)-Université de Lille-Centre National de la Recherche Scientifique (CNRS), Geospatial Information Authority of Japan, Ibaraki, ANR-15-CE04-0003,VOLCPLUME,Les panaches volcaniques: emissions, chimie/transport et impact sur l'atmosphère et le climat(2015)

Sources
ISSN: 2169-9313, EISSN: 2169-9356, Journal of Geophysical Research : Solid Earth, https://hal.uca.fr/hal-03353471, Journal of Geophysical Research : Solid Earth, American Geophysical Union, 2021, 126 (6), ⟨10.1029/2020JB020277⟩

Relation
info:eu-repo/semantics/altIdentifier/doi/10.1029/2020JB020277

Couverture
Vanuatu

Nom du journal