No abstract

Electrical resistivity tomography (ERT) and ground‐penetrating radar (GPR) were collected on the eastern side of the northern Ishtar gate in ancient Babylon, Iraq, to locate the palace wall and other surrounding walls. Due to the presence of a low resistivity (highly conductive) top layer associated with brick rubble and other debris, the GPR reflection profiles show a high‐energy attenuation, but a series of processing and filtering steps produced coherent reflections of about 2 m depth. Profile analysis shows the geometry and layering of the walls and the surrounding matrix. With the ERT, the surface conductive zone produces various distortions in ERT inverse models, making identifying the features' lower boundaries difficult. Here, we suggest that instead of analysing these two data sets independently, the integration of both reveals not just the walls but their composition and defines material in the surrounding units. This integration shows how the interpretation of the shallow features on the 3D ERT maps is improved by comparison and interpretation in conjunction with the reflections visible on both reflection profiles and the 3D GPR amplitude slices. The orientation of these features and reflections emphasizes the existence of one series of buried walls at a depth of 90–150 cm. The thickness of these walls varies between 0.25 and 1 m. Another wall‐like feature is visible only on 3D ERT maps and not with the 3D GPR slices at 2 m depth, which indicates a thickness of 11 m. It is interpreted as the palace wall, which is consistent with earlier archaeological excavations. An analysis of the geometry and composition of both wall components, perhaps of different ages, and constructed for different reasons, indicates that some shallower walls may be the remains of rooms built as residences for soldiers, or they may belong to the other ruins of northern Ishtar gate.

Electrical resistivity tomography was conducted in nine locations within ancient Babylon city, using Wenner-Schlumberger array, to map groundwater-bearing layers. The inverted models were integrated and correlated with the geological information extracted from six boreholes drilled during the 1970s. The interpreted inverse models of the Wenner-Schlumberger show identical corresponding with the lithological sequence of the boreholes. This corresponds related to the presence of one thick layer of sand deposits, with a thickness that may reach 60 m, and several thin interbedded clay layers that are locally extended. The sand layer is considered the main groundwater-bearing layer in the area. Further, the results proposed that a high discharge rate from any future boreholes which will be drilled for lowering the groundwater levels in the ancient Babylon area can easily cause a washing out of sand deposits which in turn can cause serious damages in archaeological remaining even after all measures to prevent sand washing.

A survey was conducted to investigate buried archaeological walls near the Ishtar temple in the ancient Babylon city using electrical resistivity tomography and ground‐penetrating radar methods. The survey includes applying 12 electrical resistivity tomography profiles using dipole–dipole array and a ground‐penetrating radar grid of 55 m × 50 m using 250 MHz antenna. Although the buried walls are consisting of mudbrick masonry and are embedded in a clayey environment, the electrical resistivity tomography method is still able to differentiate the tiny differences between the host materials and the buried walls, which show distinctive wall‐like features with resistivity values ranging between 9 and 15 Ω m. These features may reflect underground‐buried walls with a general width reaching about 2.5 m. The comparison of ground‐penetrating radar profiles and their corresponding electrical resistivity tomography profiles presents that the main architectures are coinciding well. The analysis of the geometry and composition of the walls around the Ishtar temple suggested that the wall‐like reflections on the ground‐penetrating radar slice at a depth between 140 and 150 cm (may be shallower) are underground‐buried walls. These wall‐like reflections show a special trend and orientation that indicate that they may be the remains of rooms belonging to two small houses or the remains of one big private house.