Present‐Day Upper‐Mantle Architecture of the Alps: Insights From Data‐Driven Dynamic Modeling

Abstract

The dynamics of the Alps and surrounding regions is still not completely understood, partly because of a non‐unique interpretation of its upper‐mantle architecture. In particular, it is unclear if interpreted slabs are consistent with the observed surface deformation and topography. We derive three end‐member scenarios of lithospheric thickness and slab geometries by clustering available shear‐wave tomography models into a statistical ensemble. We use these scenarios as input for geodynamic simulations and compare modeled topography, surface velocities and mantle flow to observations. We found that a slab detached beneath the Alps, but attached beneath the Northern Apennines captures first‐order patterns in topography and vertical surface velocities and can provide a causative explanation for the observed seismicity.

Plain Language Summary: Present‐day surface deformation, including earthquakes, plate motion, and mass (re)distribution, results from processes operating at the surface and in the interior of the Earth. Understanding these processes and their coupling is of utmost importance in light of the hazard they pose to society. The Alps provide an excellent natural laboratory to understand such coupling. Here, we use seismic tomography models to constrain its upper‐mantle architecture. We further use these models to quantify forces originating from the resolved architecture and their effects on the present‐day surface deformation. The models can reproduce first‐order patterns in the observed topography and vertical surface motions. We found a causative correlation between the presence of a shallow slab attached to the overlying lithosphere in the Northern Apennines and the seismicity in the region. Our results allow us to better understand the transfer of internal forces to the surface, thereby helping to quantify the present‐day mechanical setup of the area.

Key Points:

Statistical ensemble of S‐wave tomography models is used to infer the Lithosphere‐Asthenosphere Boundary configuration and slab geometries in the Alps.

The 3‐D upper‐mantle architecture from the statistics reproduce first‐order patterns in observed topography and Global Navigation Satellite Systems vertical velocities.

A shallow/attached slab in the Northern Apennines is consistent with the mantle depth seismicity observed in this region.