  We analyze data from four GPS campaigns carried out between 1997 and 2002 on
a network of 11 sites in the Suez-Sinai, the area of collision between the
African and the Arabian plates. This is the key area to understand how and in
which way Sinai behaves like a sub-plate of the African plate and the role
played between seismic and geodetic (long term) deformation release. Our
analysis shows that, on average, the Suez-Sinai area motion (in terms of ITRF00
velocities) matches African plate motion (NNR-NUVEL-1A model). However, the
baseline length variations show transient deformations in Sinai and across the
Gulf of Suez, reaching up a maximum value of about 1.5 cm in five years. Since
current geodynamical models do not predict significant tectonic deformation in
this area, we worked under the hypothesis that a contribute may be due to
post-seismic relaxation. Under this hypothesis, we compared the baselines
length variations with the post-seismic relaxation field associated with five
major local earthquakes occurred in the area, testing two different
viscoelastic models. Our results show that the transient deformations are
better modelled for viscosity values of 1018 Pa s in the lower crust and 1020
Pa s in the asthenosphere. However, since the modelled post-seismic effect
results modest and a certain amount of the detected deformation is not
accounted for, we think that an improved modelling should take into account the
lateral heterogeneities of crust and upper mantle structures.
