East-west extension and Holocene normal-fault scarps in the Hellenic arc

Examination of surface fault traces with Spot images and in the field corroborates the inference that the active tectonics of southern Peloponnesus and Crete are dominated by approximately north-south normal faulting and approximately east-west extension. The heights of Holocene normal-fault scarps yield first-order regional estimates of fault slip rates between 0.1 and 2-3 mm/yr. Most of the surface scarps probably ruptured during past earthquakes, such as that which destroyed Sparta in 464 B.C. On the Sparta fault the Holocene average slip rate and the recurrence time of large earthquakes may be ∼1 mm/yr and 3000 yr, respectively. The regional pattern of Quaternary faulting suggests that the east-west extension near the Hellenic subduction zone is fast (about 5%-10%/m.y.). The change from north-south to east-west extension in the late Pliocene (∼2-4 Ma) implies that the Aegean is starting to collide with the northern margin of Africa.