CRUSTAL MOTIONS IN SOUTH-EAST ASIA DERIVED FROM THE GEODYSSEA OBSERVATIONS BY DUT
SIMONS, W.J.F., B.A.C. AMBROSIUS, and R. NOOMEN 1)
In the framework of the GEODYSSEA Project, a dense network of geodetic points
in South-East Asia was measured twice in campaign style with GPS in November
1994 and in April 1996. At DUT, the complete data sets, which also include
observations from 4 additional stations in Australia and 5 nearby IGS stations,
have been processed with the GIPSY-II software. For the network deformation
analyses, the so-called 3D-Motion software, developed at DUT, was used.
First, independent free-network solutions were computed for every single day of
the campaigns. The GPS orbits were held fixed using the IGS precise ephemerides.
Also, since the networks included different receiver antenna types, the latest
version of the antenna phase center variation tables, recommended by the IGS,
were applied in the analyses. Next, the daily solutions were combined into two
separate campaign solutions which were subsequently transformed into the ITRF-94
reference frame using the IGS stations as fitting points. In a final step, the
relative motions of the stations were computed using the 3D-Motion software.
In this paper, an overview of the data analysis is given in which the quality
of the coordinate solutions is addressed. Also, an interpretation of the
observed station velocities is presented. The observed motions are in general
agreement with the motions predicted by the NUVEL-1A model, except for stations
at or near the deformation zones. The vectors recovered for the latter stations
provide significant new information which may be used as constraints in the
development of better geodynamic models. The results also provide new evidence
that the motion of the Sundaland block is somewhat different from that of the
Eurasian plate. This was confirmed by the results of an additional analysis
using a global network of IGS stations for reference. From these results a new
independent pole and vector of rotation for the Sundaland block has been
derived.
1) Delft University of Technology (DUT)
Faculty of Aerospace Engineering
Kluyverweg 1, NL-2629 HS Delft
the Netherlands
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