Present-day tectonic plate motions and crustal deformations from the DORIS space system

Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) data acquired between January 1993 and December 1996 from the SPOT-2, SPOT-3, and TOPEX/Poseidon satellites have been analyzed to determine velocities for 45 sites on eight major tectonic plates. For 28 sites far from deformation zones, the velocity estimates agree with plate model predictions. Least squares computation of poles of rotation, which model the plate motions, shows that for Eurasia, Africa, Pacific, and South America plates, the agreement is better with NUVEL-1, while for Australia, Antarctica, Nazca, and North America plates the DORIS Euler vectors are closer to NUVEL-1A. In general, DORIS results do not differ significantly from other space geodetic techniques determinations but provide better estimates for plates poorly or inhomogeneously covered by Global Positioning System (GPS), Very Long Baseline Interferometry (VLBI) and Satellite Laser Ranging (SLR) networks, such as Africa. The DORIS coverage of this plate allows discussion of intraplate deformations due to the motion of the eastern Africa part which constitues the Somalia plate. Sites located in deformation zones, such as western Eurasia boundaries, central Asia, southwestern America coast, South East Asia, show motion with respect to their own plates. Comparisons with other geodetic measurements for colocated stations, or with regional geodynamical models, show the interest of DORIS in active zones where global plate models are not valid.