GPR and Geoelectical Studies in a Historical Site in Buenos Aires, Argentina, for Locating an Old Cistern and Evaluating

We performed a geophysical study in a historical site. The main objective was to localize and characterize an old water cistern, no longer in use. Considering its expected dimensions, high density GPR data and geoelectrical dipole-dipole profiles were acquired. This allowed achieving very good resolution of the subsurface structures.

We could localize the cistern and determine that it would not be risk of collapse. While a very resistive electrical anomaly related to this structure was identified (with a diameter of approximately 1.5 m and extending up to a depth of about 0.9 m), considering the GPR results, this anomaly was associated to resistive filling material and not to the presence of a void. Below that depth, the structure seems to be filled with compacted material similar to the surrounding soil. Two other anomalous zones were detected that could correspond to structures with historical lineage. Exploratory excavations are being carried out.

Regarding the geoelectrical data, first, conventional 2D inversions were done. Then, a pseudo-3D model was built by transversally interpolating those results, and also a fully 3D inversion was performed. This aided to further improve the delineation of the anomalies.