Shear-wave splitting studies on seismograms from local earthquakes at the site of the
Mornos delta (Gulf of Corinth, Greece) has revealed a clear seismic anisotropy,
with a fast S polarization striking $N55\pm25^o$.
Magneto-telluric soundings in the frequency range
0.01 to 100 Hz on the delta showed a clear electric anisotropy, with a $N55^o
\pm 10^o $ direction for
the highest frequency. This anisotropy spans through the whole layer of sediments,
about 1 km thick. Comparison of the 1966-1972 triangulations and the
1991-1995 GPS
positions of geodetic points in and around the delta showed rapid
extension strain (2x$10^{-6}$/year) in the direction
$N340^o\pm 30^o$, perpendicular to
the fast S and the highest conductivity directions, suggestive of a causal relationship bet
ween these
observations.
We thus propose that this strain controls the two reported anisotropies, by the formation
and maintaining of fluid filled, steeply dipping antithetic faults and fractures, and
fluid filled vertical cracks, all striking $N55^o \pm 20^o$.
The source of strain is likely to be active normal
faulting near and under the delta, as
independently evidenced by the recent discovery
of nearby offshore faults, striking about $N60^o$, significantly
different from the dominant E-W strike of the major faults of the Gulf.