Three-dimensional strain tensor estimation by GPS observations: methodological aspects and geophysical applications

The aim of this paper is to describe the theoretical fundamentals, the main features and some geophysical applications of a software (STRAINGPS) suitably implemented to estimate the strain tensor from repeated GPS surveys of deformation control networks. Current softwares developed for geophysical applications generally estimate or compute bi-dimensional strain, since this is the most requested use. On the contrary, this software allows for a three-dimensional (3D) estimate of the strain tensor and does not need a subdivision of the network in triangles. It accounts for all the significant coordinate differences (or velocities) coming from repeated surveys and estimates the strain tensor components by the least squares method, starting from the hypothesis of one homogeneous strain field. Moreover, some tests to control both model adequacy and detecting outliers are performed, allowing a subdivision of the field into sub-domains with homogeneous strain field. We applied this software to three real geophysical situations. The first concerns the geodynamic (long term) induced deformation at regional scale, by estimating extensional strain rate ((0.22 ± 0.06) × 10−7) per year in central-southern Italy across the Apennines chain; the second is co-seismic strain by the assessment of the strike slip style of the Molise (central-southern Italy) earthquakes (31 October and 1 November 2002); the last regards the subsidence induced strain in the Travale-Radicondoli (central Italy) exploitation area. © 2004 Elsevier Ltd. All rights reserved.Published1-18reserve