Imaging near-surface tectonic structures using GPR: Western Eliki Fault, Gulf of Corinth, Greece

We present ground-penetrating radar data from the footwall region of the Western Eliki Fault, a normal fault on the southern shores of the Gulf of Corinth, Greece. The fault bounds the southern edge of the Eliki Plain, the site of repeated destructive earthquakes, most notably in 373 BC, 1861 AD and 1995 AD. A number of linear scarps, suggestive of recent tectonic disturbance, were identified from aerial photographs cutting an alluvial fan apron, the Nikolaiika Fan, at the eastern end of the Western Eliki Fault. In the field, the Nikolaiika Fan scarps are 0.5-1.0 m high morphological steps. These steps generally coincide with, and are indistinguishable from, the risers of agricultural terraces. To assess the likelihood of a tectonic origin, GPR common offset surveys were collected on three roads crossing the fan surface and running perpendicular to the scarps. Surveys were conducted using a pulseEKKO 100 with 50, 100 and 200 MHz antennae. GPR profiles reveal offset reflections, possible warping of reflections between offsets and regions of scattering beneath suspected fault zones, indicating that a number of surficial scarps are the surface expressions of faulting. Offsets are visible throughout the GPR profiles in sediments deposited in the last few thousand years, confirming late Holocene activity on the Western Eliki Fault. The profiles indicate that fault activity may not be confined to the main escarpment footwall, suggesting activity in the uppermost hanging-wall sediments.