C. Tiberi et al., Crustal and upper mantle structure beneath the Corinth rift (Greece) from a teleseismic tomography study, J GEO R-SOL, 105(B12), 2000, pp. 28159-28171
We report here the results of a tomographic lithospheric study in the area
of the Corinth and Evvia rifts (Greece), designed to constrain the mechanis
m of continental extension. Sixty seismological stations were deployed in t
he area for a period of 6 months, and 177 teleseismic events were recorded
by more than five stations and gave more than 2000 travel time residuals (P
and PKP phases), which were inverted to image the velocity structure down
to 200 km depth. We use both a linear and a nonlinear method to invert the
data set. The main result is a long-wavelength positive velocity anomaly lo
cated in the upper mantle, which is interpreted as the subducted African li
thosphere. The subducted lithosphere is well defined from similar to 70 km
depth down to 200 km. From synthetic tests as well as from the amplitude of
the anomaly (more than +7%) we conclude that the subduction continues belo
w 200 km. In addition, a second positive velocity anomaly of about +4% from
the surface down to 40 km depth, located north of the Gulf of Corinth, has
been found. This is interpreted as the result of a crustal thinning of sev
eral kilometers (similar to5 km), shifted to the north from the Gulf of Cor
inth and trending obliquily NW-SE. We suggest that this crustal thinning is
mainly related to the Miocene widespread extension in the Aegean and that
the Quaternary Corinth rift initiated where the dust was already thinned. T
he different styles of deformation of the eastern and western part of the r
ift are consistent with this interpretation. No clear velocity anomaly can
be related to the Evvia rift.