Global positioning system constraints on plate kinematics in the southern alps at the nubia-Eurasia boundary

We present and interpret deformation velocities from continuous Global PositioningSystem (GPS) observations at 42 sites around the Adriatic region (central Mediterranean)to investigate the active tectonics of the Nubia-Eurasia plate boundary in thenortheast of Italy, the seismically most active region of the Southern Alps. In total,1600 days of GPS observations, from June 2002 to November 2006, were processedusing GAMIT/GLOBK. In detail, we present our processing scheme that is based ona three-step approach: i) estimation of station coordinates, atmospheric zenith delay,orbital and Earth orientation parameters using daily GPS observations and applyingloose constraints to geodetic parameters; ii) combining, on a daily basis, the looselyconstrainedsolutions with loosely-constrained SOPAC solutions; and combining thedaily combinations into monthly averages while adjusting the final x2 to 1 by rescalingthe daily h-files (method to account for white noise); and iii) defining the referenceframe, determining the site velocities and estimating the error by including both the effectof white noise and random walk component (monument instability). We estimatethe random walk component station by station using the "realistic sigma" algorithm ofHerring (2003b).All eight stations of the Friuli Regional Deformation Network (FReDNet), whichform the focus of this chapter, present at least 2.5 years of data, and so exceed theminimum time span for a reliable determination of deformation velocity. The geodetic data indicate shortening of the crust in the region, with southern Friuli moving NNWtowards northern Friuli at the relative speed of 1.6 to 2.2 mm/yr. One of the eight processedFReDNet stations (i.e. CANV - Caneva), situated closely north to the activePolcenigo-Maniago Thrust, is moving faster than its expected long-term, geologic velocity.As there are no other plausible reasons for this discrepancy, we interpret thisanomalous high velocity to be an indication of a locked thrust and predict that strain isaccumulating to the north of it. © 2010 by Nova Science Publishers, Inc. All rights reserved.