Springer Online Journal Archives 1860-2000
Architecture, Civil Engineering, Surveying
Abstract We have used Very Long Baseline Interferometry (VLBI) data to compute the site coordinates and constant velocity components for 29 fixed antenna sites and 25 mobile sites. The three singularities which occur in the adjustment with respect to the rotation of the system have been resolved by a constraint holding the net rotation of seven fixed antennas, distributed on the stable portions of four of the geologic plates, to the net rotation for these sites as defined by the NNR-NUVEL1 no net rotation model. In order to achieve a minimally constrained adjustment of this type we have found it necessary to use a new adjustment procedure in which we solve for the coordinates of each site at the weighted mean epoch of all the observations involving that site. Using the results of the above solution we have computed the departure for each site from the NNR-NUVEL1 rigid plate model. These departures show that the transition zone in western North America from the region of rigidity to the plate boundary is at least 400 km wide, in general agreement with Ward (1988,1990).
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