Insights into present-day crustal motion in the central Mediterranean area from GPS surveys

Abstract

Summary In this paper we present observations of crustal motion related to a large GPS network located in the central‐western Mediterranean area. Velocities are obtained by the analysis of more than 30 observing sites at which at least three different GPS campaigns were carried out in the time span 1991–1999. The results are presented both in the ITRF96 reference frame and with respect to a Eurasian fixed reference frame. The sites located along the northern African margin, in Sicily and southern Italy show prevalent northeastward movements with a mean velocity of roughly 0.7 cm yr−1. The relatively dense network available in the southern Apennines led us to try a tentative estimate of the average strain rate in this zone, resulting in a maximum extension of 0.021 ± 0.006 × 10−6 yr−1 normal to the chain. In Ionian Greece the two sites located south of the Kephallinia discontinuity (Lefkas and Kastro Ilias) consistently indicate a south to southwestward motion at an average rate of roughly 15 mm yr−1.

Seismic strain and seismogenic stress regimes in the crust of the southern Tyrrhenian region

“…Alternative modelling of the regional geodynamics was proposed by Mantovani et al [31^33] who explained the strain pattern in the Mediterranean area by adopting the convergence of the African, Arabian and Eurasian blocks as the only driving mechanism of tectonic activity in the region. Debate on the most appropriate model is still open, basic constraints are in particular expected from current developments of geodetic monitoring [34].…”

Geodetic strain in peninsular Italy between 1875 and 2001

“…Estimates of the extension rate evaluated from summation of seismic moment tensors of recent and historical earthquakes range from 0.3 mm/yr in the northern Apennines to 2.0 mm/a in the central and southern Apennines [Selvaggi, 1998], though earlier estimates have ranged from 3 mm/yr to as high as 10 mm/yr [Westaway, 1992], with differences between these estimate reflecting different choices of seismic catalogue and M s -M o relationship. Existing geodetic measurements suggest that between 3 -6 mm/ yr of extension takes place across the Apennines, but with only limited information on whether the strain is localized in regions of active faulting [D' Agostino et al, 2001;Anzidei et al, 2001]. In this paper we evaluate active crustal deformation in the Italian peninsula over time span of 126 years.…”

Earthquake focal mechanisms and stress inversion in the Irpinia Region (southern Italy)

“…The inversion of these fault plane solutions, which were mainly normal faults, showed an extensional stress field along a NE-SW direction. Analysis of GPS data also provides a significant SW-NE extension in the Southern Apennines (Anzidei et al 2001). …”

“…In particular, Amato and Montone (1997) and Montone et al (1999) studied the active stress in Fig. 13 Stress field orientations obtained from former studies using: 1 GPS data (Anzidei et al 2001); 2 strong earthquakes (Montone et al 1999); 3 breakout data (Montone et al 1999); 4 focal mechanisms of the Southern Apennines earthquakes Frepoli and Amato (2000); 5 this study the Southern Apennines through the analysis of breakout and fault plane solution data of moderate to strong earthquakes. They inferred that the Southern Apennines is ongoing through a NE-SW extension, with a horizontal σ 3 and a vertical σ 1 .…”