Geophysical Characterization of Archaeological Sites in Active Seismic Zones: The Case of the “Basilica Bath” at Hierapolis (Turkey)

Since 1988, the Hierapolis-Pamukkale site has been included in the UNESCO list for the uniqueness of its archaeological ruins and thermal installations within an extraordinary natural setting. The site is located in the active seismic area of the Denizli basin, which has been affected over the centuries by recurrent strong earthquakes that destroyed numerous ancient cities, some of which were later abandoned due to heavy damage. Hierapolis to this day exhibits faulted architectural relics distributed throughout the site, crossed by natural petrified water channels, and generally related to the largely exposed main faults visible in the SSE-NNW direction. The Basilica Bath is a partially collapsed monumental building located outside the northern part of the Hierapolis walls, where the primary faults are supposed to run, but have not been clearly identified. In this paper, we present the results of electrical resistivity tomography (ERT) carried out to detect archaeological features and, in a selected line, coupled with seismic refraction tomography (SRT) to identify possible fault directions related to the partial collapse of the Basilica Bath. Geophysical measurements provide new data on supposed buried remains, and a likely fault configuration that may have caused the partial collapse of the building, supporting further studies on its reconstruction and reuse in ancient times.