ISTerre seminar

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Crustal and Upper Mantle Structure Variations Along the Alpine Chain Revealed by Teleseismic Full Waveform Inversion

Wednesday 10 December 2025 - 14h00

Najmieh Mohammadi - ISTerre
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The tectonics of the Alps and Apennines arise from complex interactions among the African, Eurasian, and Iberian plates, modulated by asthenospheric mantle dynamics. This system originated with the closure of the Neo-Tethys Ocean during the Middle Jurassic, triggering a sequence of geodynamic processes including subduction, mountain building, slab rollback, and back-arc basin formation. These interactions have produced a highly heterogeneous and laterally variable lithospheric structure across the region. Understanding the crustal and upper mantle architecture is therefore essential for constraining the geodynamic evolution of the Alpine–Apennine system. High-resolution imaging methods are required to elucidate these deep Earth processes. In this study, we developed the first high-resolution, three-dimensional elastic multiparameter model extending to a depth of 700~km using Full Waveform Inversion (FWI) of 84 teleseismic earthquakes recorded by the AlpArray, SWATH-D, and CIFALPS2 networks. The model simultaneously inverts for $V_P$, $V_S$, and density. A semi-automated data selection and quality control procedure was implemented to ensure consistency and reliability across the large dataset. The FWI results reveal significant crustal and mantle-scale features beneath the Alps. They delineate crustal anomalies, variations in fault zone velocities, and the subducted European lithosphere beneath the Adriatic region. The Moho deepens progressively from the southwestern to the northwestern Alps, with the Central Alps exhibiting a deeper Moho than the Western Alps. In the Eastern Alps, two distinct Moho structures are observed: a flat Adriatic Moho at approximately 40~km depth and a European Moho extending southward to 60–65~km, subducting along the Penninic Front. At upper mantle depths, the results indicate continuous subduction of the European slab beneath the Western and Central Alps to around 250~km. The model highlights complex, laterally variable slab geometries in the Western Alps and confirms that the Alpine and northern Apenninic slabs remain distinct above 300~km depth. In the Central Alps, the European slab subducts actively beneath the Po Basin without evidence of detachment, although localized slab gaps may occur. In the Eastern Alps, the results support a near-vertical subduction of the Alpine slab, clearly separated from the Adriatic slab, and suggest possible asthenospheric upwelling associated with slab retreat.

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Organizing team : Ondes et structures

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

Informations de visio :

https://univ-grenoble-alpes-fr.zoom.us/j/95496607088?pwd=UuSVyVX0SCxaFwJ8BOzQujEfEjydwi.1