Ground-penetrating radar and electrical resistivity tomography studies in the biblical Pisidian Antioch city, southwest Anatolia

Abstract

Pisidian Antioch was founded as a military base in the Hellenistic period around 300 bc. A consecutive archaeological structure, extending 55 m long, mainly includes two adjacent abscissas and a wall remain thought to be a watchtower. An integrated geophysical survey including ground-penetrating radar (GPR) and electrical resistivity tomography (ERT) techniques was conducted to determine the existence of counterparts of this structure in a small-scale area. GPR scans acquired via zigzag mode using 500 MHz antenna along 45 parallel lines were evaluated by a series of basic data processing steps. Considering the results obtained, two-dimensional (2D) ERT data collected in a restricted area using Wenner-alpha array along 41 parallel lines were inverted using 2D and three-dimensional (3D) tomographic inversion schemes. On the basis of the findings obtained from various GPR and ERT imaging techniques, the existence of one of the abscissa, displaying dimensional parameters being in good accordance with those of ones still standing on the west side of the survey area was clearly revealed. Moreover, some regular anomalies, which can be attributed to the remains of the watchtower in question and various wall ruins, were successfully traced from the GPR depth slices. The existence of an antisymmetric geometry for the consecutive archaeological structure under investigation was also determined in the survey area. Combining all of that information, a possible 3D virtual image of the military headquarters was then created, and this pointed out a small square quadriburgia characteristic of the structure investigated. Thus, we can conclude that the integration of GPR and ERT and imaging techniques used in the evaluation were quite effective to provide useful prior information for the subterranean targets in the non-excavated parts of the ancient city. An archaeological evaluation by trial trenching is therefore required to confirm the results of the archaeo-geophysical survey in the investigation area.