The northern Adriatic plate underwent Permian-Mesozoic rifting and was later shortened by three orogenic belts (i.e., Apennines, Alps and Dinarides) developed along three independent subduction zones. The inherited Mesozoic horst and graben grain determined structural undulations of the three thrust belts. Salients developed in grabens or more shaly basins, whereas recesses formed regularly around horsts. A new interpretation of seismic reflection profiles, subsidence rates from stratigraphic analysis, and GPS data prove that the three orogens surrounding the northern Adriatic plate are still active. The NE-ward migration of the Apennines subduction hinge determines the present-day faster subsidence rate in the western side of the northern Adriatic (> 1 mm/year). This is recorded also by the SW-ward dip of the foreland regional monocline, and the SW-ward increase of the depth of the Tyrrhenian sedimentary layer, as well as the increase in thickness of the Pliocene and Pleistocene sediments. These data indicate the dominant influence of the Apennines subduction, which controls the asymmetric subsidence in the northern Adriatic realm. The Dinarides front has been tilted by the Apennines subduction hinge, as shown by the eroded Dalmatian anticlines subsiding in the eastern Adriatic Sea. GPS data suggest that southward tilting of the western and central Southern Alps, whereas the eastern Southern Alps are uplifting. The obtained strain rates are on average within 20 nstrain/year. The horizontal shortening obtained from GPS velocities at the front of the three belts surrounding the northern Adriatic plate are about 2-3 mm/year (Northern Apennines), 1-2 mm/year (Southern Alps), and < 1 mm/year (Dinarides). The shortening directions tend to be perpendicular to the thrust belt fronts. The areas where the strain rate sharply decreases along a tectonic feature (e.g., the Ferrara salient, the Venetian foothills front) are proposed to be occupied by locked structures where stress is accumulating in the brittle layer and thus seismically prone. Finally, we speculate that, since the effects of three independent subduction zones coexist and overlap in the same area, plate boundaries are passive features

The external part of the Northern Apennines accretionary wedge in northern Italy is buried beneath its fast subsiding and asymmetric foreland basin in the Po Plain. It is characterized by a diffused noncylindrical geometry resulting in salients and recesses in the study area, namely, the Cremona salient, the Parma recess, and the Ferrara salient. The interpretation of borehole and seismic reflection data suggests that the thrust belt is characterized by thin‐skinned tectonic style. Two main décollement levels have been identified: a basal décollement located in the Upper Carnian units (San Giovanni Bianco Clay and Raibl Group) and a shallow décollement located in the late Eocene‐Oligocene formations (Gallare Marls). The décollement surfaces dip SSW toward the hinterland of the accretionary prism, parallel to the steep (>10°) regional monocline. The geometry of the seismically active Northern Apennines system of salients and recesses is essentially controlled by the interplay of two factors: (i) the lateral facies variations of the stratigraphic units hosting and controlling the location and depth of the décollement levels and (ii) the slope of the basal décollement. Salients occur where, due to the inherited variable stratigraphy of the Mesozoic‐Cenozoic Tethyan passive margin, the shaly formations hosting the two décollements are well developed allowing larger forward propagation of the thrust wedge. Recesses are instead associated to erosional‐nondepositional areas. Moreover, salients are more pronounced where the flexural behavior of the Adriatic subducting slab has generated a steeper geometry of the foreland monocline and consequently of the basal décollement.

The Adria microplate is the foreland of the oppositely verging Apennines and Alps or Dinarides fold-thrust belts associated to the related subduction zones. Along its western margin, the Adria plate hosts the active Northern Apennines accretionary prism, which is buried under the Adriatic Sea and the Po Plain. The interpretation of seismic reflection profiles and borehole data allowed us to define the geometry of the transition from the Apennines fold-thrust belt to its undeformed foreland. Moreover, continuous GPS (CGPS) data from offshore hydrocarbon platforms anchored to the seabed of the northern Adriatic plate allow to measure present-day kinematics. Although the CGPS signals are affected by non-tectonic components associated with hydrocarbon extraction, the integration of geodetic analysis, subsurface geological reconstructions, and analytical modeling allowed us to constrain the ongoing tectonic activity. Shortening is currently accommodated by aseismic slip along the basal detachment, likely accumulating elastic energy along the frontal ramp that may eventually seismically slip. Our multidisciplinary study suggests that the study area may not be sheltered from relevant seismic sequences similar to the Mw 6 Emilia 2012 events and that the occurrence of potential seismogenic sources in the area should be carefully evaluated. Similar studies may be useful to constrain the present-day activity in other marine areas and to identify potential and hitherto unrecognized seismogenic sources along the entire Apennines belt and other accretionary prisms worldwide.

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