La fédération
Intranet
Séminaire ISTerre
Study of the mantle transition zone by combining earthquake data and seismic noise data: application to the Alps and Massif Central
vendredi 9 octobre 2026 - 10h00
Piel Pawlowski - ISTerre---
The mantle transition zone plays a crucial role in mantle dynamics, particularly regarding mantle convection. Long studied via seismology, this zone is primarily characterized by sharp wave velocity jumps resulting from phase changes in olivine, a mineral abundant in the upper mantle. However, the limited sensitivity and resolution of so-called "global" methods make in-depth study challenging. Investigating these discontinuities at a local scale is difficult due to both their depth and their complexity, specifically their topography, which varies significantly with mantle composition and temperature. Receiver functions, a particularly robust method, have yielded significant insights into this zone and its spatial heterogeneity. In this manuscript, we propose combining this method with a newer observable: body-wave reflections detected in ambient noise correlations. To better constrain the mantle transition zone and understand these two observables, we model them using realistic mantle composition profiles, testing our methods against complex velocity gradients. These synthetic data reveal significant differences in how the two methods respond to compositional changes, particularly regarding broad velocity gradients, where reflected wave amplitudes drop drastically. Observing reflections from the mantle transition zone is now possible thanks to a better understanding of the microseismic wavefield, which requires selecting favorable sources located at great distances from the observation points. We therefore investigated the biases between the theoretically reconstructed Green’s function and synthetic cross-correlations, which depend on these specific source distributions. We demonstrated that such biases are small in Europe, but that noise conditions for this imagery technique can’t be applied anywhere due to source localization. Finally, we jointly compared and interpreted observables from both methods at a European scale, revealing interesting similarities alongside notable differences in key tectonic regions. The observed amplitudes align well with our synthetic modeling and reveal a distinct trend beneath the southwestern Alps, suggesting the presence of water. Signals resulting from conversions and reflections at the 410 km and 660 km discontinuities become more complex in certain areas, appearing sometimes in both methods and sometimes in only one. Meanwhile, measurement variations beneath the Massif Central remain slight but indicate a deepening of both discontinuities, linked either to actual topography or to velocity variations in the upper mantle. This work thus offers new possibilities for interpreting the composition and topography of the transition zone in Europe.
Equipe organisatrice : Ondes et structures
Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères
Informations de visio :
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
Lire la suite
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
Lire la suite
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
Lire la suite
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
Lire la suite
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
Lire la suite
Study of the mantle transition zone by combining earthquake data and seismic noise data: application to the Alps and Massif Central
vendredi 9 octobre 2026 - 10h00
Piel Pawlowski - ISTerre
Equipe organisatrice : Ondes et structures
Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères
Lire la suite
Statistical physics of creep rupture of heterogeneous materials
jeudi 15 octobre 2026 - 11h00
JUAN CARLOS VERANO ESPITIA - ISTerre - Aalto University (Finlande)
Equipe organisatrice : Mécanique des failles
Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères
Lire la suite
The Seismic Response of Faults to Weak Perturbations: A New Probe Into Earthquake Physics and Fault State
vendredi 6 novembre 2026 - 11h00
Eric Beaucé - ISTerre
Equipe organisatrice : Cycle sismique et déformations transitoires
Salle Dolomieu, Maison des Géosciences, 38400 Saint Martin d'Hères
Lire la suite
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
Lire la suite