On the tectonic processes along the Hellenic Arc

A. G. GALANOPOULOS

Abstract


On the grounds of existing geophysical data one
might be allowed lo conclude t h a t the origin of t h e stress field in the Ionian
center (Ceplialonia-Zante-Patras) at t h e northwestern margin of the Aegean
microplate is r a t h e r shallow and in the southeastern center (Dodecanese-Crete)
is surely under the crust.
In the area occupied by the second center of higher earthquake activity
t h e relief of the Moho-discontinuity is shallower and smoother in comparison
to t h a t derived from g r a v i t y and seismic d a t a for t he area of t h e northwestern
center. Another difference derived from the fault-plane solutions is t h a t the
Ionian center is seated in a region of horizontal pressure; the second center in
the southeastern Aegean Sea belongs to a region of paramount horizontal
tension.
In the western side of the Hellenic arc the high sediment supply rate,
combined with a thickening of the E a r t h ' s crust along the Ionian zone, is
interpreted as evidence t h a t accretion has occurred there until recently or
may still be occurring locally; plate consumption, if any, is rather low.
The existence, 011 t h e other hand, of two very deep subparallel trenches
with little fill southeast of Crete (Pliny trench, Strabo trench), combined
with a very high subcrustal activity in the southeastern margin of t h e Aegean
Bubplate, suggest that the subduction rate at the northern boundary of the
African plate must be relatively high; 110 p l a t e accretion is expected to occur
there.

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DOI: https://doi.org/10.4401/ag-4932

Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X