Abstract:

In this paper we present a combination of several near surface geophysicalΒ investigation techniques with high resolution remote sensingΒ image interpretations, in order to define the groundwater flow pathsΒ and whether they can be affected by future seismic events. A seasonalΒ spring (Amvrakia) located at the foot of Meteora pillars near the villageΒ of Kastraki (Greece) was chosen as a test site. The Meteora conglomeraticΒ formations crop out throughout the study area and areΒ characterized by large discontinuities caused by post Miocene till presentΒ tectonic deformation [Ferriere et al. 2011, Royden and PapanikolaouΒ 2011]. A network of groundwater pathways has been developedΒ above the impermeable marls underlying the conglomeratic strata. OurΒ research aims to define these water pathways in order to investigate andΒ understand the exact mechanism of the spring by mapping the exposedΒ discontinuity network with classic field mapping and remote sensingΒ image interpretation and define their underground continuity with theΒ contribution of near surface geophysical techniques. Five Very Low FrequencyΒ (VLF) profiles were conducted with different directions aroundΒ the spring aiming to detect possible conductive zones in the conglomeraticΒ formations that the study area consists of. Moreover, two ElectricalΒ Resistivity Tomography (ERT) sections of a total length of 140m wereΒ carried out parallel to the VLF profiles for cross-checking and verifyingΒ the geophysical information. Both techniques revealed important conductiveΒ zones (<200 Ohm m) within the conglomerate strata, which weΒ interpret as discontinuities filled with water supplying the spring, whichΒ are quite vulnerable to displacements as the hydraulic connections betweenΒ them might be easily disturbed after a future seismic event.

Notes:

Applied Geophysics; Electrical tomography; hydrogeology; 3D modellingAnnals of Geophysics6