Mantle Structure Beneath the Greater Alpine Region From Teleseismic Full P‐Waveform Inversion

Abstract AlpArray data were employed to infer a new mantle model of the Alps from teleseismic full P‐waveform inversion. It features hybrid numerical forward modeling in the time domain, compression of wavefields by Fourier transform at selected frequencies, the use of frequency domain waveform sensitivity kernels and a multi‐scale approach by successively increasing frequencies with each iteration. Full waveform inversion has an excellent resolution in the crust and the shallow upper mantle, hence no a priori crustal corrections are applied. Above 90 km depth, we find a thick crustal root beneath the Alps bounded by the Alpine fronts reaching depths of 50–70 km. The root of the Apennines is sharply bounded to the east and north by the Apenninic Front (AF) and is about 50 km thick. Commencing at about 90 km depth, a band of vertically hanging slabs presumably associated with the collision of Europe and Adria beginning in the Eocene roughly follows the Periadriatic Fault System and extends to depths of 250 km. The slabs are generally detached from shallow fast lithosphere along a common shear horizon located at 90–100 km depth. In the central and western Alps, weak connections of the slabs with shallow fast European lithosphere are observed along narrow corridors. A near‐vertical slab beneath the Apennines commences at 70 km depth and extends vertically to 400 km depth. This slab still seems to be weakly connected to Adriatic lithosphere to the north and east of the AF.