Séminaire ISTerre

Volcano monitoring and geothermal exploration from seismic network cross-correlations: source- and noise-based approaches

mercredi 9 novembre 2022 - 10h00
Jean Soubestre - ISTerre/Séminaire Post-doc (café-croissant à 9h45)
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Volcanic activity implies volcano hazards associated with volcanic unrests and eruptions, but also opportunities including boosted agriculture productivity, volcano tourism and geothermal energy. In this seminar, I will present results from two newly developed methods based on seismic network cross-correlations to study volcanoes, with both noise- and source-based approaches. On the one hand, we developed an ambient noise tomography (ANT) method using nonlinear multiscale inversions to image volcanoes for a geothermal exploration purpose. The method is designed to overcome typical challenges of ANT at volcanoes including pronounced topography effects and high velocity contrasts. It also uses a transdimensional inversion at depth, providing the uncertainties associated with the obtained velocity model, which is crucial for geothermal exploration studies. To date, it has already been successfully applied to different datasets from the Canary Islands. On the other hand, we developed a network covariance matrix method to monitor the seismic activity of volcanoes. The method enables detection, clustering, location and classification of any kind of seismo-volcanic signal, including the continuous volcanic tremor for which traditional seismic methods based on phase picking are not adapted. It has been successfully applied on both real-time and existing datasets at different spatial scales, with network aperture ranging from continental (~4000 km) to regional (~100 km) down to local (a few kms) scale. In terms of perspective, we show that the developed network covariance matrix method can be applied on any kind of data in the form of network time series (e.g. DAS, GNSS, accelerometers, infrasounds, hydrophones, inclinometers,...) and is useful for characterizing seismic tremor from different origins (volcanic but also tectonic, hydrothermal, glacial, geothermal, landslides). Finally, this latter source-based method can be complementary to noise-based approaches and extend their applicability in time.

Equipe organisatrice : Organisation labo

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