Forgotten Faults that are Compatible with the Kinematics of the External Hellenides (Greece)

Current GNSS data from southwestern Greece indicates an extension rate of 6 mm.yr^-1 in the NE-SW direction, i.e., perpendicular to the Hellenic subduction zone. Additionally, there is a significant NW-SE extension component, parallel to the trench. Around the Gulf of Corinth and the Gulf of Evia, the extrusion of the Anatolian microplate transitions into pure N-S extension at rates of up to 15 mm.yr^-1. Farther west, this extension evolves into a complex network of strike-slip faults in the Ionian region (e.g., Patras, Cephalonia, etc.). These movements are often accommodated by fault systems that originated up to 3 million years ago, with offsets reaching several kilometers.

In the External Hellenides, older faults associated with late-orogenic collapse or early supra-subduction extension also exist. These include structures active during the intense Aegean crustal thinning in the Mio-Pliocene, such as in the Cretan Sea and the Gulf of Argos. In the Peloponnese, remnants of late-orogenic fault systems define the borders of Quaternary sedimentary basins like Megalopolis, Sparti and Olympia.

From new tectonic mapping and GNSS data in southwestern Greece, we discuss if some older, currently seismically inactive faults could be aligned with modern deformation gradients and potentially exhibit creep or interseismic strain accumulation.