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Thrust fault ruptures during earthquakes do not often propagate down to the brittle‐ductile transition. Lithological variations control the behavior and depth of regional basal thrusts and decollement planes. Thrust fronts may be discontinuous along strike, limiting the dimension of single coseismic ruptures. These factors control the maximum expected magnitude in one region. This is the case of Italy where the convergence of few millimeter per year in the Apennines accretionary prism and along the retrobelt of the Alps generates compressional earthquakes with moderate to strong magnitudes. Here, using geological and geophysical data, we first compile a map of the undulated active basal thrust decollement for Italy that occurs from 1 to 17‐km depth. Then, we verify the relationship between the length of seismogenic ruptures in thrust faults (Lf) and the maximum depth of thrust faulting (zmax) of related earthquakes and find that their ratio (Lf/zmax) ranges between 2 and 4. Finally, we compute the potential seismogenic volume and estimate the maximum magnitude using an empirical relationship that multiplies the decollement depth and the Lf/zmaxratio. Maximum calculated magnitude is 6.7 ± 0.37 (depending on Lf/zmaxand fault dip angle), consistent with the largest magnitude of thrust‐related earthquakes recorded in Italy (6.5–7.0). Lower magnitudes are predicted in the Ionian Seas at the external front of the Apennines where smaller crustal volumes are involved, whereas higher magnitudes are expected in the southern Po Basin, the western Adriatic Sea, Sicily offshore, and the Southern Alps where the decollement is deeper and the brittle volumes are far greater. Earthquakes are due to different kinds of crustal fault ruptures, and the observed magnitude depends on the rupture dimension, hence on the involved brittle volume. Those related to thrust faults generate magnitudes lower than expected if the decollement is shallow, whereas the magnitudes increase where the decollement is deeper. This is the case of Italy where many factors can explain the moderate to strong (M 5–7) observed magnitudes recorded so far in the contractional areas of the country: (i) the slow convergence rate (few millimeters per year) observed for the Apennines and Alps; (ii) the thrusts do not cut down the entire seismogenic crust; and that (iii) thrusts are undulated and segmented along strike, limiting the dimension of the fault rupture. We compile a map of the thrust decollement depth for Italy that is situated between 1–17 km. Then, we quantify the along‐strike discontinuity, verifying the ratio between thrusts length and faulting depth of related earthquakes. Finally, we estimate the maximum expected magnitude for the study area. Calculated magnitudes are consistent with those occurred for thrust‐related earthquakes in Italy, pointing to the importance of knowing the depth and the lateral continuity of faults to correctly assess the seismic potential of a region. The basal active thrust decollement is mapped on the Italian accretionary prismsWe define the relationship between the length of thrusts ruptures and maximum faulting depth (Lf/zmax) for Italian earthquakesSeismic volumes calculated from faulting depth and Lf/zmaxratio provide a good estimation of expected magnitudes

The evolution of the Apennine wedge has seen the time‐space migration of the forebulge, foredeep, thrust wedge, and back‐arc extension phases in the wake of the Eastward rollback of the subducting Adria slab. In this framework, thrusting and post‐orogenic extensional faulting have occurred in two parallel forelandward‐migrating ribbons, with extensional deformation overprinting or partly exploiting anisotropies of the inherited thrust system. Here, we explore the tectonic framework and the timing of thrusting and subsequent negative inversion of the Circeo thrust, one of the major thrusts in the inner portion of the central Apennines, with the main aim to constrain the timing and mode of the compression to extension switch. Structural analysis, carbonate C and O and clumped isotopes analysis, X‐ray diffraction of clay minerals, and U‐Pb dating of calcite slickenfibers have been integrated with seismic interpretation, cross‐section balancing, and 1D burial and thermal modeling. We show that the Circeo thrust developed during Langhian‐Serravallian time. Its extensional reactivation is dated at the Serravallian, during the stacking of an underlying thrust slice, before the onset of Pliocene back‐arc extension in the area. Combination of our data with the age of thrusts, extensional basins, and base of the foredeep infill of the central Apennines, demonstrates that forelandward migration of the foredeep‐thrust system occurred at variable velocities. Accelerations and decelerations are synchronous, respectively, with the opening of the Liguro‐Provençal and Tyrrhenian back‐arc basins and with the interluding quiescent period. We build a balanced cross section across the Circeo thin‐skinned thrust, one of the innermost structures of the central ApenninesThe section is validated by means of carbonate C and O and clumped isotopes, U‐Pb dating, seismic interpretation and burial modelingA regional synthesis of the age of foredeep infill, thrusts, and extensional basins for the central Apennines is presented We build a balanced cross section across the Circeo thin‐skinned thrust, one of the innermost structures of the central Apennines The section is validated by means of carbonate C and O and clumped isotopes, U‐Pb dating, seismic interpretation and burial modeling A regional synthesis of the age of foredeep infill, thrusts, and extensional basins for the central Apennines is presented

Two main types of subduction zones can be distinguished: (1) those where the subduction hinge migrates away from the upper plate; and (2) those in which the subduction hinge migrates toward the upper plate. Apart from a few exceptions, this distinction seems to apply particularly for W-directed subduction zones and E- or NE-directed subduction zones, respectively. Moreover, the rate of subduction is larger than the convergence rate along W-directed subduction zones, whereas it is smaller along E- or NE-directed subduction zones. Along W-inclined slabs, the subduction rate is the convergence rate plus the slab retreat rate, which tends to equal the backarc extension rate. Along E- or NE-dipping slabs, the shortening in the upper plate decreases the subduction rate, and no typical backarc basin forms.Relative to the mantle, the W-directed slab hinges are fixed, whereas they move west or southwest along E- or NE-directed subduction zones. The single vergent accretionary prism related to W-directed subduction zones is formed at the expenses of the shallow layers of the lower plate. The orogens generated by E- and NE-dipping subductions are double vergent since the early stages, and upper plate rocks mostly compose them until continental collision takes place, eventually involving the rocks of the lower plate more extensively. The convergence/shortening ratio in this type of orogens is higher than 1 and is inversely proportional to the viscosity of the upper plate. The higher the viscosity, the smaller the shortening and faster the subduction rate. The convergence/shortening ratio along W-directed subduction zones is instead generally lower than 1.W-directed subduction zones provide larger volumes of lithospheric return into the mantle than the opposite E- or NE-directed subduction zones. The latter may contribute to refertilize the shallow upper mantle. These observations suggest that subduction zones are passive features with respect to the far-field velocity of plate motions and the relative "eastward" mantle flow, implicit with a net "westward" rotation of the lithosphere.

The Tyrrhenian back‐arc basin developed at the rear of the E‐ward migrating Apennine fold‐and‐thrust belt, with northward decreasing rollback of the subducting Adria slab leading to northward fading of back‐arc extension. The northern portion of the Tyrrhenian basin is made of thinned continental crust, whereas in the central/southern portion extension eventually evolved to oceanic crust production. In this framework, a long‐lasting debate concerns the existence of a >200 km long transform zone along the 41st parallel, which should separate the two portions of the Tyrrhenian basin. At its eastern termination, a branch of the presumed transform zone enters the Tyrrhenian margin of the Apennine belt and occurs as an accommodation zone made of a ribbon of extensional faults and related basins. This accommodation zone, which separates areas of mutually perpendicular extension directions, is here introduced, described, and named the Ponza‐Alife accommodation zone. Interpretation of seismic lines and new structural and stratigraphic data from this accommodation zone have been used to constrain the pre‐orogenic and syn‐orogenic architecture of the subducting plate and the Plio‐Quaternary back‐arc extensional stage. Our data indicate that the studied zone retraces a deep‐seated transform fault system located in the subducting plate and inherited from an Early Jurassic rifting episode, which caused the lateral juxtaposition of different rift domains in the subducting plate. We propose that during collision and trench retreat, this lateral juxtaposition has controlled differential retreat of the subducting plate across the studied zone, forcing the development of the Ponza‐Alife accommodation zone in the overlying back‐arc basin's margin. The Ponza‐Alife accommodation zone segmenting the Apenninic margin of the Tyrrhenian back‐arc basin is introducedStructural and stratigraphic data, and seismic interpretation allowed us to unravel the evolution of this accommodation zoneThe accommodation zone originated from tearing in the downgoing plate reworking Jurassic faults that segmented the associated rift system The Ponza‐Alife accommodation zone segmenting the Apenninic margin of the Tyrrhenian back‐arc basin is introduced Structural and stratigraphic data, and seismic interpretation allowed us to unravel the evolution of this accommodation zone The accommodation zone originated from tearing in the downgoing plate reworking Jurassic faults that segmented the associated rift system

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. Seismic reflection profiles in the northern Adriatic Sea allow to reconstruct the Apennines fold‐thrust belt geometry and its forelandOffshore CGPS data allow computation of the active shortening in the accretionary prismAnalytical modeling provides a first‐order estimation of the current slip rate of the unlocked and locked surfaces of the basal decollement

The Oman Mountains expose Permo‐Mesozoic shelf rocks of Arabia overridden by continental slope/basinal sediments and Semail Ophiolites during Late Cretaceous. A major syntaxis is represented by the Musandam Peninsula and Dibba Zone. The overthrusting of allochthonous units onto the Musandam shelf carbonates initiated during the Cenomanian. Structural analyses in the Musandam Peninsula constrained top‐to‐the‐west thrusting that took place 74–60 Ma ago (U‐Pb datings of synkinematic calcites), about 15–30 Ma after the obduction of the Semail Ophiolite. The Dibba faults exhibit a first interval of thrusting (top‐to‐the‐west) followed by dextral slip. We propose that SW vergent thrusts, initially parallel to those of the Central and Southern Oman Mountains, were subsequently rotated to their present‐day NE‐SW strike during the development of the syntaxis and then reactivated by dextral slip. Mixed layers illite‐smectite (I‐S) constrain the thermal evolution of the passive margin sequence and of the allochthonous deep‐water sediments. In particular, the proximal Hawasina unit (Hamrat Duru) and Sumeini groups of the Dibba Zone are characterized by long‐range ordered mixed layers I‐S with an illite content of 90–95%, whereas Musandam carbonate units show mixed layers I‐S with illite layers ranging from 80–90%, indicating deep diagenetic conditions. Such levels of thermal maturity were acquired during the Late Cretaceous emplacement of a 3.5‐km‐thick pile of allochthonous units, which were removed by erosion and denudation since the Campanian. U‐Pb dating of synkinematic calcite vein highlights reactivation of thrusts at 13.2 Ma, likely due to the involvement of the Musandam area in the Arabia‐Eurasia collision. Musandam faults display multiple kinematics acquired between 74 and 13 MaMixed layers illite‐smectite paleothermometers indicate deep diagenetic conditionsLevels of thermal maturity were acquired during the Late Cretaceous obduction