CRUSTAL DEFORMATIONS IN THE MEDITERRANEAN AREA COMPUTED FROM SLR AND GPS OBSERVATIONS

Space geodesy provides an efficient technique to determine contemporar y crustal deformations. This paper discusses the computation of tecton ic motions in the Mediterranean area from observations acquired by Sat ellite Laser Ranging (SLR) and Global Positioning System (GPS) instrum ents. The SLR contribution is based on measurements on LAGEOS-1, taken in the period September 1983 to December 1992. For this analysis, the period was divided into 38 consecutive intervals. An independent stat ion coordinates solution was computed for each subinterval. During thi s 9.3 year interval, the WEGENER project organized four mobile SLR obs ervation campaigns in the Mediterranean region, resulting in three or four independent position solutions for the majority of the sites in t his area. The GPS contribution is based on observations taken during t he Euref'89 campaign, which took place from May 16 to 28, 1989, and du ring the WEGENER/GPS-92 campaign, which took place from July 29 to Aug ust 3, 1992, as a sub-campaign for the IGS Epoch'92 campaign. Most of the space-geodetic reference points in the Mediterranean area were occ upied with GPS receivers during both campaigns, providing two valuable additional position solutions. The time-series of position solutions for each station are converted into individual station motion vectors. The horizontal components of the latter reveal a clear and consistent picture of the deformations taking place in the area: the northward m otion of Arabia, the lateral escape to the west of Anatolia, the NE-SW expansion in the Aegean Basin and the northward motion of Africa bein g transduced into the central part of the Mediterranean. The results a re in agreement with the qualitative kinematical models for this regio n, derived from geophysical evidence. The vertical station motion solu tions are generally very small and insignificant from a statistical po int of view. The internal and mutual consistency of the independent SL R and GPS network solutions is also investigated. The agreement is sho wn to be at the level of 5-20 mm.