CONICET | Buscador de Institutos y Recursos Humanos

In this work we present the application of the strain analysis approach to site velocity vectors derived from repeated geodetic Global Positioning System (GPS) observations in order to investigate the deformation of the earth crust along an active tectonic plate boundary. The region under investigation is located in the southernmost part of South America, in the Argentine side of Tierra del Fuego island. It includes the Magallanes-Fagnano Fault System (MFFS), the only on-land segment of the South American/Scotia tectonic plates boundary. The MFFS represents a left-lateral transform fault. The presented analysis is based on precise GPS observations in a network of 30 stations and spanning 14 years. Using the Bernese GPS software in combination with state-of-the-art trategies, models and products, site velocity vectors were determined for each station with an accuracy of less than 0.2 millimeter per year. The obtained horizontal velocities were used as an input for a strain analysis. Our results demonstrate that the strain analysis is a convenient tool to reveal and analyze the spatial pattern of the crustal deformation within the GPS network. Geodynamically stable regions are clearly distinguished from an active deformation zone along a 30 km-wide belt centered on the main trace of the fault system. Within this deformation zone a change from stretching (transtensional deformation) on the East to predominant shortening (transpressional deformation) on the West is detected. Further in sights are obtained by the correlation of the strain rates with the vertical velocities and rotation rates. The identification of rigid zones in either sides of the MFFS allows a more precise determination of the relative transform velocity between the South American/Scotia tectonic plates.

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