No Relative Movements between South American and Scotia Plates in Tierra Del Fuego
In December, 1993, a twenty points precise GPS network for cartographic and geodetic purposes was first established in the argentine portion of the Tierra del Fuego Island. The northern part of the network (15 points) is placed on the Southamerican plate (SAM), three points are situated on the Scotia plate and two points are located near the main fault. Redundant baselines were measured in such a way that each point is directly related to at least three neighbor points. During December, 1994 and December, 1995, the network was partially remeasured (12 common points) to detect tectonic movements between SAM and Scotia plates. TRIMBLE 4000 SSE receivers were used during the 1993 campaign, and Ashtech Z12 receivers were used in 1994 and 1995 campaigns. Each time, the individual baselines were processed using the GPSurvey software, and the Trimnet program was used to compensate the redundant baselines. Precise IGS orbits were used in all cases. The estimated accuracy of each individual network was 1 cm in latitude and longitude and 2 cm in ellipsoidal height.
The repetitivity of the coordinates between the results of the different campaigns, after a Helmert transformation is better than 1 cm in latitude and longitude and about 2 cm in ellipsoidal height. Due to the relatively small distances between the extremes of the network (about 150 km), the spatial coordinates were transformed to plane Gauss Krüger coordinates and a two dimension transformation was performed (a scale factor, one rotation angle and X, Y origin offsets). The repetitivity of the plane coordinates is better than 1 cm. In conclusion, no movements were detected in this region during the last two years, to this level of accuracy.
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