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 Southalpine thrust front in northeastern Italy obtained by integrating GPS, InSAR and leveling data. The area is characterized by the presence of sub-parallel, 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 of NW-SE shortening associated with the Adria-Eurasia plate convergence, but the horizontal GPS velocity gradient across the mountain front provide limited constraints on the geometry and slip-rate of the several sub-parallel thrusts. In terms of vertical velocities, the three geodetic methods provide consistent results showing a positive velocity gradient, of ~ 1.5 mm/a, across the mountain front, which can be hardly explained solely by isostatic processes. We developed a 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 are 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 (LD = 9.1 km and slip-rate = 2.1 mm/a) 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 often seismological and geomorphological evidence of active tectonics is 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, 2005, 2008; Devoti 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; Pezzo et al, 2012; 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).…”

Mechanical Response of Shallow Crust to Groundwater Storage Variations: Inferences From Deformation and Seismic Observations in the Eastern Southern Alps, Italy

“…In this work we study a segment of the Adria‐Eurasia plate boundary in North‐Eastern Italy (Figure 1), hit by strong historical earthquakes (e.g., the Mw 6.5, 1695 Asolo earthquake; Rovida et al., 2020) and where the larger part of plate convergence is presently accommodated across a south‐verging fold‐and‐thrust belt (Anderlini et al., 2020; Serpelloni et al., 2016). The main thrusts are, from the internal parts to the foreland, the Valsugana thrust, the Belluno thrust, and the Bassano‐Valdobbiadene thrust (BVT), the latter being associated with a morphological relief of ∼1,200 m above the plain, known as Pedemountain flexure (Figure 1).…”

Common mode signals and vertical velocities in the great Alpine area from GNSS data

“…The Eastern Southern Alps is the region where the largest part of the Adria-Eurasia converge is accommodated (1-3 mm yr -1 ), through active thrust faults and shortening (Serpelloni et al, 2016). Here, maximum uplift rates are likely due to interseismic deformation, and their position, across the belt, is driven by thrust fault geometries, slip-rates and locking depths (Anderlini et al, 2020).…”

“…We focus on the vertical component, which is nominally less accurate and precise than the horizontal ones, because this mountain belt is characterized by significant ground uplift and spatial vertical velocity gradients that are correlated with topography (Serpelloni et al, 2013). The present-day convergence between Adria and the Eurasian plate is largely accommodated in the Eastern Southern Alps (e.g., Serpelloni et al, 2016) where the Adriatic lithosphere underthrusts the Alpine mountain belt, and here part of the observed vertical uplift is associated with active tectonics (Anderlini et al, 2020). Conversely, in other Alpine domains, positive vertical velocities most likely derive from a complex interplay of deep-seated geodynamic and isostatic processes (e.g., Sternai et al, 2019).…”