S U M M A R YGravitational signatures of subduction are a major feature of the Earth's gravity pattern, being visible as lineaments parallel to the arc-trench systems. The novelty of our study resides in the simulation of this subduction fingerprint via a newly developed dynamic subduction model based on the finite-element approach, which includes the compositional stratification of the lithosphere into a light upper crust and a dense lithospheric mantle. Crustal material sinks in the mantle in proximity to the top of the slab due to the viscous dragging forces and off-scraping of the overriding plate. We show that the sinking of light crustal material from both the subducting and overriding plates to depths of the order of 200 km may be responsible for a trough of about 100 MGal extending 100-200 km in a direction perpendicular to the trench. This anomaly is superimposed on a global positive gravity anomaly due to thermal contraction of the mantlelithosphere system. The negative gravity anomaly due to compositional stratification of the crust has comparable magnitude and horizontal extent of that due to the negative dynamic topography of the trench. The gravity patterns from compositional stratification of the crust and from dynamic trench topography are evaluated for different tectonic subduction styles related to active convergence, with and without roll-back. In general, we found that case without roll-back produces a broader and smoother dynamic topography gravity anomaly than with roll-back, while the gravity signature from compositional stratification is less sensitive to the style of subduction.

S U M M A R YThe thermomechanic evolution of the lithosphere-upper mantle system during Calabrian subduction is analysed using a 2-D finite element approach, in which the lithosphere is compositionally stratified into crust and mantle. Gravity and topography predictions are cross-checked with observed gravity and topography patterns of the Calabrian region. Modelling results indicate that the gravity pattern in the arc-trench region is shaped by the sinking of light material, belonging to both the overriding and subduction plates. The sinking of light crustal material, up to depths of the order of 100-150 km is the ultimate responsible for the peculiar gravity signature of subduction, characterized by a minimum of gravity anomaly located at the trench, bounded by two highs located on the overriding and subducting plates, with a variation in magnitude of the order of 200 mGal along a wavelength of 200 km, in agreement with the isostatically compensated component of gravity anomaly observed along a transect crossing the Calabrian Arc, from the Tyrrhenian to the Ionian Seas. The striking agreement between the geodetic retrieved profiles and the modelled ones in the trench region confirms the crucial role of compositional stratification of the lithosphere in the subduction process and the correctness of the kinematic hypotheses considered in our modelling, that the present-day configuration of crust-mantle system below the Calabrian arc results from trench's retreat at a rate of about 3 cm yr −1 , followed by gravitational sinking of the subducted slab in the last 5 Myr.