GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 3.2 GNGTS 2024 Fig. 1 – a) Locaton of the Valley of the Temples; b) aerial view of the Sanctuary of Chthonian deites; c) locaton of EM surveys and d) locaton of ERT surveys. Methods and Data Collecton The electromagnetc survey method is one of the widely used techniques in archaeological research. It can identfy the contrast of magnetc and electrical propertes between buried structures and surrounding lithotypes (Bigman, 2012). This method is used to measure the electric currents produced in the subsurface by electromagnetc feld inducton using transmitng and receiving coils in the frequency domain (FDEM) (Di Maio et al. 2016). The EM survey was performed on an area of about 3000 m², with an acquisiton step of 0.5 m (Fig. 1c). Along each profle, the data were collected using a sampling step of 0.50 m. The equipment used is an AEMP14 multfrequency electromagnetometer, which consists of three coils: one transmitng and two receiving coils. The distance between the transmitng coil and the frst receiving coil is 1.5 m, and the distance to the second receiving coil is 2.5 m. The device is capable to operate at 14 frequencies ranging from 2.5 kHz to 250 kHz. Electrical resistvity tomography (ERT) is a geophysical method with a wide range of applicability. It allows to obtain 2D sectons and 3D models showing the distributon of the resistvity in the subsoil (Tong and Yang, 1990; Sasaki, 1992). The investgated area was divided into 4 sectors, investgated by 38 ERT surveys spaced 0.50 m apart in sector 1, while the spacing increased to 1 m in sectors 2, 3 and 4 (Fig. 1d). The acquisitons were performed with two quadripolar confguratons for each linear array: DD (Dipole-Dipole) and MGA (Multple Gradient Array).