Late Quaternary Tectonic Activity of the Udine-Buttrio Thrust, Friulian Plain, NE Italy

Abstract

The NW-SE trending Udine-Buttrio Thrust is a partly blind fault that affects the Friulian plain southeast of Udine in NE Italy. It is part of a wider fault system that accommodates the northward motion of the Adriatic plate. Although seismic reflection data and morphological evidence show that the fault was active during the Quaternary, comparably little is known about its tectonic activity. We used high-resolution digital elevation models to investigate the surface expression of the fault. Measured vertical surface offsets show significant changes along strike with uplift rates varying between 0 and 0.5 mm/yr. We then analyze a topographic scarp near the village of Manzano in more detail. Field mapping and geophysical prospections (Georadar and Electrical Resistivity Tomography) were used to image the subsurface geometry of the fault. We found vertical offsets of 1–3 m in Natisone River terraces younger than 20 ka. The geophysical data allowed the identification of deformation of the fluvial sediments, supporting the idea that the topographic scarp is a tectonic feature and that the terraces have been uplifted systematically over time. Our findings fit the long-term behaviour of the Udine-Buttrio Thrust. We estimate a post-glacial vertical uplift rate of 0.08–0.17 mm/yr recorded by the offset terraces. Our results shed light on the Late Quaternary behaviour of this thrust fault in the complicated regional tectonic setting and inform about its hitherto overlooked possible seismic hazard.

Present-Day Surface Deformation in North-East Italy Using InSAR and GNSS Data

“…Considering the presence of active thrusts and the termination of the Dinaric strike-slip faults, such as Idrija, Predjama, and Raša faults in the area, we suggest a potential correlation between the deformation pattern and the tectonic structures (i.e., buried thrusts and transcurrent and transpressive faults) in the area. The activity of these buried structures is also suggested by Viscolani et al [121], whose estimated vertical rates agree with our observations (Figure 7). Moreover, Serpelloni et al [15] identified residual westwards, sub-mm/yr, motions in an Adria-fixed reference frame near Udine.…”

Surface deformation analysis in Northeast Italy by using PS-InSAR and GNSS data 

“…4.11), as confirmed by the GNSS data. The low uplift rates detected close to the thrusts near Udine also agree with the estimated rates in the study of Viscolani et al (2020). North of the JOAN site, we observe a velocity gradient up to 2 mm/yr across the Carnic-Julian Alps, which gradually decreases toward Austria (~ 1mm/yr).…”

“…Finally, the Friulian plain is characterized by the presence of south-verging thrusts, especially around Udine, like the Udine-Buttrio and Medea thrusts, buried by the thick Quaternary sediment cover (Burrato et al, 2008;Viscolani et al, 2020). Despite the low seismic activity, based on geological evidence, the tectonic structures are potentially capable of generating earthquakes (Galadini et al, 2005;Burrato et al, 2008).…”

Geodynamic and seismotectonic model of a long-lived transverse structure: The Schio-Vicenza Fault System (NE Italy)

“…5) has experienced repeated opposite strike-slip movements over time. The emplacement of N-trending basaltic dykes north of PTJ in the damage zone of the SVF suggests dextral transtension (Zampieri et al, 2003;Fondriest et al, 2012) during the Paleogene, when the area was deformed by nearly E-W extension (Zampieri, 1995). During the initial stages of the Neogene contraction, the SVF may have slipped by sinistral movements, partly inverted by subsequent dextral movements, when the wedge structure north of the triple junction opened the zipper of the merging faults.…”