New geophysical "scan" of the Alps helps explain current deformation field

Pelvoux massif and Briançonnais area © Stéphane Schwartz
New ambient background geophysical data provide an unprecedented 3D image of the deep geometry of the boundary between mantle and continental crust beneath the Western Alps, also known as the Moho. These high-resolution data enable the deep geometry to be correlated with sub-surface geological data.

These data show the presence of a cold, rigid mantle body located 20 kilometers below the Po plain south of Turin. This portion of the Adriatic mantle acts as an indentor, controlling the deformation of the European plate.

In detail, the geometry of the Adriatic mantle, divided into two units (ASB and ALI), is responsible for the instantaneous deformation field recorded by seismicity. In this context, the current distribution of earthquakes (representing instantaneous deformation) observed at the scale of the Alps is a response to the counter-clockwise rotation of the Adriatic plate and its indenter imposed by the global NW/SE shortening between Africa and Europe.

Seismotectonic and structural model of the Western Alps showing the relationship between the surface deformation field and the deep geometry revealed by wave tomography (Vs). Indentation of the European crust by the Adriatic mantle (ALI) is controlled by counter-clockwise rotation of the Adriatic plate in a global context of convergence between the two plates.

Reference

Schwartz, S., Rolland, Y., Nouibat, A., Boschetti, L., Bienveignant, D., Dumont, T., Mathey, M., Sue, C., Mouthereau, F., 2024. Role of mantle indentation in collisional deformation evidenced by deep geophysical imaging of Western Alps. Communications Earth & Environment, DOI.

Scientific contact

– Stéphane Schwartz, maître de conférence UGA/ISTerre