Crustal velocity and strain-rate fields in Italy and surrounding regions: new results from the analysis of permanent and non-permanent GPS networks

Abstract

SUMMARY We present a new geodetic velocity solution for Italy and the surrounding areas, obtained from an analysis of continuous and survey‐mode Global Positioning System observations collected between 1991 and 2002. We have combined local, regional and global networks into a common reference frame velocity solution, providing a new detailed picture of the regional‐scale deformation field in the central Mediterranean. Our velocity estimates are computed with respect to a new stable Eurasian reference frame, constraining the kinematics of the greater African–Eurasian plate boundary system in the study area. We provide strain‐rate values for the main seismotectonic districts, which are in good agreement with the seismic deformation inferred from earthquake focal mechanisms. The southern Tyrrhenian area, Calabria, the Apennines, the southeastern Alps, the southern Dinarides and the Albanides display deformation rates at the order of 20–30 nanostrain yr−1. The Corsica–Sardinia block moves according to Eurasian Plate motions, and there is no indication that the opening of the Tyrrhenian is still active. The Pelagian and Sicilian domains are separated by a northwest–southeast discontinuity, the Sicily Channel rifted area, and marginally significant relative motion between the Pelagian Plateau and the African Plate is also observed. The southern Tyrrhenian is affected by north–south compression and accommodates up to 50 per cent of the Africa–Eurasia relative plate motion, whereas the Calabrian Arc exhibits ∼2 mm yr−1 northwest–southeast extension. The observed deformation pattern suggests the presence of a major approximately north–south tectonic discontinuity separating the Sicilian and Calabrian domains. An extensional boundary observed along peninsular Italy coincides with the distribution of seismogenic faults along the axis of the Apennines. This boundary separates a Tyrrhenian and an Adriatic domain with diverging velocities, orientated north–NNW‐ward and northeastward, respectively. The Apennines are extending perpendicularly to the chain axis at rates of less than 3 mm yr−1, and only in the outer northern Apennines indications of active shortening are observed. Insignificant deformation is observed in the western Po Plain and the western Alps, while the central and eastern Alps display north–south shortening. The eastern Adriatic domain is shortening perpendicular to the Dinaric front with strain rates increasing from north to south. The locus of collision between the Aegean/Balkan system and the Adriatic and Ionian domains is marked by the Kephalonia fault system, which accommodates up to 20±1 mm yr−1 of right‐lateral motion. The deformation pattern observed in the peri‐Adriatic domain is well described by a counter‐clockwise rotation of the Adriatic microplate around a pole located in the western Alps.

Tectonics, climate, and mountain topography

“…[51] Alps (Eastern) (EAL): We rely on GPS results showing that the Apulian peninsula rotates about an axis in or near the western Po Basin and converges with Eurasia at 2.2 AE 1 mm/yr [Calais et al, 2002b], which agree sufficiently well with GPS results of Battaglia et al [2004] and Serpelloni et al [2005], and with the rate of shortening measured by Benedetti et al [2000] for the bounding thrust fault of the Alps in southern Italy.…”

“…[52] Alps (Western) (WAL): We rely on the GPS results of Calais et al [2002a], and corroborated by several other studies [Calais et al, 2002a;D'Agostino et al, 2008;Serpelloni et al, 2005;Weber et al, 2010], which show essentially no present-day convergence across the western Alps, but extension and strike-slip movement parallel to the belt and internal deformation of it. This range may be a singular case, because active shortening is null but recent geological history shows that shortening across the range occurred during the Pliocene, and has apparently stopped since then.…”

“…[72] Dinarides (DNR): We use the GPS rate of 4.5 AE 1 mm/yr given by Bennett et al [2008], which supersedes the rates of 6 AE 1 mm/yr of Battaglia et al [2004] and Serpelloni et al [2005].…”

Holocene environmental history of a small Mediterranean island in response to sea-level changes, climate and human impact

“…(Lambeck and Bard, 2000;Lambeck and Purcell, 2005;Peltier, 2004). But even if the Corso-Sardinian block was not affected by significant tectonic processes during the Holocene (Conchon, 1975;Lambeck et al, 2004;Serpelloni et al, 2005), the glacio-hydro-isostatic component in this area is more difficult to estimate and the amplitude/timing of late-Holocene relative sea-level rise (RSLR) is a matter of debate (Pirazzoli, 2005). In Corsica and on the Southern France coasts, many studies, suggest a sub-linear RSLR of about 2.5 to 1.5 m during the last 5000 years, with a rapid rise until 1500 years BP, then a stabilization close to the modern sea-level 500 years ago (Laborel et al, 1994;Morhange et al, 1996Morhange et al, , 2001Vacchi et al, 2016a;Vella and Provansal, 2000).…”

Error propagation in time-dependent probability of occurrence for characteristic earthquakes in Italy

“…In Italy, the fatalities are due to moderate-to-strong events in regions inhabited for a long time and subjected to small deformations. Only two events in the earthquakes catalog (CPTI Working Group 2004) are referred to as M > 7 earthquakes (but magnitudes are still controversial), the deformation rates from geodetic measurements are in the order of 20-30 nanostrain per year (e.g., Serpelloni et al 2005) in this part of the Mediterranean, and consequently, long-term slip rates of Italian faults rarely exceed 1.5 mm/year. Small values, if compared with those of other seismically active regions.…”