Along-strike variations of strain partitioning within the Apennines determined from large-scale multi-temporal InSAR analysis
Résumé
In the Apennine Mountains of the Italian Peninsula, GPS data display 3–4 mm/yr of divergent motion oriented
N50◦E between the Adriatic and Tyrrhenian coastlines. However, the mechanisms driving this extension remain
debated and along-strike variations of extension within the actively deforming belt remain poorly constrained.
Here, we derived the first large-scale extensional and vertical velocity field for the Apennines by multi-temporal
InSAR analysis of 7 years of Sentinel-1 data at the scale of the entire range, improving the spatial resolution and
vertical accuracy of existing GPS measurements. The results reveal along-strike variations of extensional rates
and gradients, with extension concentrated on single fault systems in the north, consistent with the loci of
seismicity and recent moderate earthquakes, and distributed throughout the central Apennines, where the range
is widening. Vertical surface displacements do not resolve any active long-wavelength uplift of the orogenic belt
and, on average, show more subsidence than uplift relative to the Tyrrhenian and Adriatic coasts. This work
provides the first InSAR-based geodetic map of differential extension and uplift within the Italian Peninsula. Our
results are compatible with a pure shear extensional model of the crust, driven by both boundary and gravita-
tional forces.