HR: 10:50h
AN: G32A-03    [Abstracts]
TI: A New Tectonic Plate Model Based on ITRF2005: Implications on the Global Kinematics
AU: * Fernandes, R M
EM: rmanuel@di.ubi.pt
AF: DEOS, TUDelft, Faculty of Aerospace Engineering, Delft, 2629 HS, Netherlands
AU: * Fernandes, R M
EM: rmanuel@di.ubi.pt
AF: UBI, CGUL, IDL, Department of Computer Sciences R. Marquês d'Avila e Bolama, Covilhã, 6201-001, Portugal
AU: Bos, M S
EM: msbos@fc.up.pt
AF: Astronomical Observatory of University of Porto, Monte da Virgem, V. N. Gaia, 4430-146, Portugal
AU: Ambrosius, B A
EM: B.A.C.Ambrosius@tudelft.nl
AF: DEOS, TUDelft, Faculty of Aerospace Engineering, Delft, 2629 HS, Netherlands
AB: Tectonic plate models have been routinely computed in the last years using space-geodetic solutions of the motions of discrete points on the Earth's surface. Such models have been referenced with respect to different realizations of the ITRS (International Terrestrial Reference System). In particular, several models were produced based on the different ITRF solutions. This is the case of DEOSVel (Fernandes et al., 2003), which used the official ITRF2000 velocity solutions for 154 sites (supplemented with 14 own-computed solutions in Africa) to estimate the angular velocity for the stable part of eight major tectonic plates. A new realization of ITRS, ITRF2005, was recently (October 2006) released. It presents position/velocity solutions for a total of 338 different sites, based on four different techniques: GPS, VLBI, SLR and DORIS. Although the number of sites decreased (ITRF2000 presented solutions for 487 sites), the derived ITRF2005 velocity solutions are based on a much longer time-series of positions (until the beginning of 2006) than the previous ITRF2000 velocity solutions (until mid 2000). Consequently, the reliability of the estimated solution improved substantially for most of the stations. In this work, we present a new tectonic plate model based on ITRF2005: DEOSVel05a. This model is based exclusively in the ITRF2005 velocity solutions in order to ensure the best internal consistency of the input data. However, the formal uncertainties associated with the ITRF2005 solutions are too optimistic because temporal correlations between observations were not taken into account. Therefore, we investigated the implications of using a rescaled covariance matrix to compute the plate model uncertainties. We compute our own position solutions for a global set of GPS stations. For each station, the spectral index of the power-law noise in the time- series was estimated and new uncertainties of the motion estimates derived. By computing the ratio between these values and the formal errors provided in the ITRF2005 solution, an average scale factor was estimated and applied to the input covariance matrix used to derive the angular velocities in the least squares sense. We will discuss the implications of using DEOSVel05a instead of other space-geodetic derived models to constrain the present-day kinematics of the stable part of the analyzed tectonic plates. In particular, we focus on the variation of the angular velocity estimates for Americas and Africa. We demonstrate that for many plates, the estimates provided by these different models are converging. However, for some plates (e.g., Somalia), the number of available data points is still not enough to provide a robust answer about the present-day kinematics of these tectonic blocks.
DE: 1209 Tectonic deformation (6924)
DE: 1229 Reference systems
DE: 3040 Plate tectonics (8150, 8155, 8157, 8158)
DE: 8149 Planetary tectonics (5475)
SC: Geodesy [G]
MN: 2007 Joint Assembly