Characterization of a Pre-Trajan wall by integrated geophysical methods

The purpose of this study was to characterize a pre-Trajan mosaic-decorated wall structure located beneath the Cryptoporticus of the 'Baths of Trajan' complex in Rome. The surveyed wall is 15m long, 0.9m wide and 3 to 5m high. Ground penetrating radar (GPR) and P-wave seismic refraction tomography profiles were used to reconstruct the wall's inner structure, generate a map of the fractures and to evaluate the seismic velocities of the building materials. The wall was surveyed with horizontally and vertically dense GPR profiles and two seismic lines. The seismic lines and GPR profiles were capable of detecting a discontinuity between brick and travertine materials that compose the wall. The combined interpretation of the two non-invasive techniques allowed us to locate weak zones and fractures. This rapid, non-destructive and multi-parametric approach has proved to be effective for characterizing the current status of the wall and the results will be used by archaeologists to evaluate the wall's integrity and to preserve the structure in the future archaeological excavations.