New insights into active tectonics and seismogenic potential of the Italian Southern Alps from vertical geodetic velocities

Abstract

Abstract. This study presents and discusses horizontal and vertical geodetic velocities for a low strain rate region of the south Alpine thrust front in northeastern Italy obtained by integrating GPS, interferometric synthetic aperture radar (InSAR) and leveling data. The area is characterized by the presence of subparallel, south-verging thrusts whose seismogenic potential is still poorly known. Horizontal GPS velocities show that this sector of the eastern Southern Alps is undergoing ∼1 mm a−1 of NW–SE shortening associated with the Adria–Eurasia plate convergence, but the horizontal GPS velocity gradient across the mountain front provides limited constraints on the geometry and slip rate of the several subparallel thrusts. In terms of vertical velocities, the three geodetic methods provide consistent results showing a positive velocity gradient, of ∼ 1.5 mm a−1, across the mountain front, which can hardly be explained solely by isostatic processes. We developed an interseismic dislocation model whose geometry is constrained by available subsurface geological reconstructions and instrumental seismicity. While a fraction of the measured uplift can be attributed to glacial and erosional isostatic processes, our results suggest that interseismic strain accumulation at the Montello and the Bassano–Valdobbiadene thrusts it significantly contributing to the measured uplift. The seismogenic potential of the Montello thrust turns out to be smaller than that of the Bassano–Valdobbiadene fault, whose estimated parameters (locking depth equals 9.1 km and slip rate equals 2.1 mm a−1) indicate a structure capable of potentially generating a Mw>6.5 earthquake. These results demonstrate the importance of precise vertical ground velocity data for modeling interseismic strain accumulation in slowly deforming regions where seismological and geomorphological evidence of active tectonics is often scarce or not conclusive.

Active Fold‐Thrust Belt to Foreland Transition in Northern Adria, Italy, Tracked by Seismic Reflection Profiles and GPS Offshore Data

“…At the time scale of a few years, Adria plate kinematics can be considered as a stationary process (Anderlini et al, 2020;D'agostino et al, 2005Devoti et al, 2008). Therefore, we consider the linear velocity model as the most suitable description of the tectonic displacement at the CGPS points; however, the offshore platforms may be affected by local ground deformation due to the exploitation of gas fields, and CGPS velocities may thus vary with time.…”

“…In order to estimate the current slip rate of the major identified faults, we simulated the surface deformation associated with an uniform slip over the regional thrust detachment, by using a simple 2-D modeling approach, largely applied to different tectonic domains worldwide (e.g., Anderlini et al, 2020;Fialko, 2006;Ponraj et al, 2019;Vergne et al, 2001). The computation of a 2-D profile model allowed us to simulated an infinite wide (perpendicular to the profile) regional thrust detachment, avoiding lateral deformation effects ( Figure 6).…”

Paleo-Seismicity in the Euganean Hills Province (Northeast Italy): Constraints From Geomechanical and Geophysical Tests in the Schio-Vicenza Fault Area

“…The estimated vertical slip rate of the Euganean Hills is at least 0.4 mm/y once compared with Mt. Netto (Livio et al, 2020) and Montello (Anderlini et al, 2020). Even though during glacial stages, the alluvial plain grew remarkably faster than the Euganean Hills (3-7.5 times faster during the LGM), the uplift of the latter could have filled the gap during interglacial times, when the alluvial sedimentation was lower.…”

“…If the slip rate of the frontal part of the Euganean Hills was at least 0.4 mm/y, as estimated by Livio et al (2020) for Mt. Netto near Brescia, and by Anderlini et al (2020) for the Montello thrust, then ∼2^10 6 years could have been sufficient to deform and expose the Scaglia Rossa after the formation of the gouge layer.…”

Comment on se-2021-19

“…Historical seismicity (e.g. Galadini et al, 2005) and clustering of (micro-)seismic hypocenters (Romano et al, 2019;Anderlini et al, 2020;Jozi Najafabadi et al, 2020) along these fault systems and morphological evidence of fault surface rupture (Moratto et al, 280 2019;Romano et al, 2019) indicate that this younger phase of shortening is still active.…”