Séminaire ISTerre

« How active volcanism changes topography: Applications of radar interferometry techniques for the monitoring of ground deformation and the tracking of erupted volumes.» 

jeudi 31 mars 2022 - 11h00
Fabien Albino - ISTerre
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Over the past three decades, satellite radar interferometry (InSAR) has shown its ability to detect ground deformation and topographic changes associated with volcanic activity. Although InSAR has a much better spatial resolution than ground instrumentation, most of the InSAR ground deformation signals are still detected a-posteriori due to delays for acquiring and processing the data. Thanks to the Sentinel-1 mission, the near real-time monitoring of volcanic ground deformation is now achievable with InSAR, as data are freely available only 1-2 hours after acquisitions. Using the automated InSAR processing chain LïCSAR, we are able to produce time series of ground deformation to response rapidly to ongoing volcanic crisis such as the 2017 seismic crisis at Agung volcano. For this tropical volcano, we first show that the corrections of atmospheric signals in the interferograms are crucial to extract ground deformation signals. We then detect a persistent 5 km radius uplift signal of 8-10 cm on the north flank of Agung volcano prior to the 2017 November eruption. Numerical inversion of InSAR data using 3D FEM models indicates that the ground deformation signal is consistent with a deep sub-vertical magma intrusion located at midway between Agung and its neighbor, Batur caldera.  Bi-static missions such as TanDEM-X are designed for the production of high-resolution Digital Elevation Model (DEM), as phase changes are only dependent on terrain. Although TanDEM-X DEMs have been widely used to quantify the thicknesses of lava flows, until now, the method had not been applied to pyroclastic flows, because the thin deposits are often emplaced in steep-sided valleys where DEM accuracy is expected to be low. Here, we demonstrate the benefit of TanDEM-X DEMs to characterize the spatial distribution of the topographic changes associated with the emplacement of the Pyroclastic Density Currents (PDC) during the 2018 Fuego eruption. Erosion and collapses of 30 m occurred close to the summit whereas the deposits (up to 25 meters) mainly accumulated inside the main channel of the SE flank. Analysis of the volume budget indicates that a large proportion of the PDC volume originated from the summit collapse, which confirms that bulking increases the run-out distance of pyroclastic flows and explains why the 2018 eruption was particularly destructive.

Equipe organisatrice : Grands Séminaires ISTerre

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères

Informations de visio :

 https://univ-grenoble-alpes-fr.zoom.us/j/92459210214?pwd=bkp1NElHZ2wzc3AwaEZmOCtaMGNmUT09

“Minimalist seismology”: studying earthquakes with sparse instrumentation

jeudi 17 septembre 2026 - 11h00

Mathieu Causse - ISTerre

Equipe organisatrice : Organisation labo

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères

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Stable‑to‑dynamic expansion of fault slipping area through fluid injection observed in laboratory experiments using a sub‑meter scale specimen

vendredi 18 septembre 2026 - 14h00

Takatoshi Ito  - Université de Tohoku, Japan

Equipe organisatrice : Mécanique des failles

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères

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Tectonics, Mantle Dynamics and Coupled Lithosphere-Mantle-Core Evolution of Earth and Other Rocky Worlds

jeudi 24 septembre 2026 - 11h00

Paul Tackley - ETH Zurich

Equipe organisatrice : Grands Séminaires ISTerre

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères

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Tectonics, Mantle Dynamics and Coupled Lithosphere-Mantle-Core Evolution of Earth and Other Rocky Worlds

jeudi 24 septembre 2026 - 11h00

Paul Tackley - ETH Zurich

Equipe organisatrice : Grands Séminaires ISTerre

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères

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Apport des expériences analogiques pour la modélisation et le suivi en temps réel de la propagation du magma en profondeur : Exemple du Rift Est Africain

jeudi 1er octobre 2026 - 11h00

Virginie Pinel - ISTerre

Equipe organisatrice : Organisation labo

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères

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A t-on encore besoin de plaques pour expliquer la tectonique de la vallée du Rhône et des Alpes Occidentales ?

vendredi 2 octobre 2026 - 11h00

philippe VERNANT - Geosciences Montpellier

Equipe organisatrice : Tectonique active et sismicité

Salle Dolomieu, Maison des Géosciences, 38400 Saint Martin d'Hères

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TBA

vendredi 2 octobre 2026 - 14h00

Hugo Boulze - 

Equipe organisatrice : Cycle sismique et déformations transitoires

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères

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TBA

vendredi 9 octobre 2026 - 11h00

Eric Beaucé - ISTerre

Equipe organisatrice : Cycle sismique et déformations transitoires

Salle Dolomieu, Maison des Géosciences, 38400 Saint Martin d'Hères

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TBA

vendredi 20 novembre 2026 - 11h00

Farzaneh Mohammadi - ENS Paris

Equipe organisatrice : Cycle sismique et déformations transitoires

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères

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