Abstract
We use a newly updated GPS dataset and the GPS Imaging technique to show
that the relief of the Apennines Mountain chain in Italy is currently
increasing along its entire length by 1-2 mm/yr. We image positive
uplift along the entire length of the Apennine crest including the
northern Apennines, Calabria and northern Sicily. The maximum uplift
rate is aligned with the topographic drainage divide, the greatest
elevations and the zone of horizontal extension accommodating
east-northeast translation of the Adriatic microplate relative to the
Tyrrhenian Basin. Uplift occurs in a 100 - 150 km wide zone with a
profile similar to the long wavelength topography, but not to shorter
wavelength topography generated by active faulting and erosion. A zone
of lower amplitude uplift aligns with the restive volcanic fields and
high geothermal potential west of the Apennines, e.g., at Campi Flegrei,
Alban Hills, and Monte Amiata-Larderello. Several factors including
consistency of the geodetic rate with geologic uplift rates, and
incompatibility with transient hydrological or earthquake cycle effects
imply that it is a long-lived feature. Uplift occurs despite that the
expected consequence of extension is crustal thinning and subsidence,
suggesting a causal relationship between gravitational forces and active
extension. Anomalies in gravity and upper mantle seismic velocity
suggest that elevation gain is driven by forces originating in the
mantle. We use these observations to address the hypothesis that these
forces result from upward flow of asthenosphere beneath the Apennines,
although the spatial and temporal scale of the mantle circulation is
unclear.