EMI data from an archaeological resistive target revisited

LASCANO, EUGENIA; MARTINELLI, PATRICIA; OSELLA, ANA

NEAR SURFACE GEOPHYSICS

EUROPEAN ASSOC GEOSCIENTISTS & ENGINEERS

Año: 2005 vol. 4 p. 395 - 400

1569-4445

In a previous work we presented the analysis and interpretation of geophysical data acquired at Floridablanca archaeological site located in Patagonia, Argentina. The electromagnetic induction method (EMI) was used to quickly detect and localize the anomalous zone of interest. Afterwards a quantitative characterization of the structure responsible for this anomaly was achieved by inverting geoelectrical data. In this work we re-analyze EMI data to study if this data could also provide us with quantitative information about our target, which presents a resistive signature with respect to the host medium. First, an alternative visualization of the data is done that allows us to clearly detect some features of the anomaly that could not be distinguished before. It also makes evident which of the configurations used in the data acquisition presents the best sensitivity and resolution. Then, the EMI data corresponding to the anomalous zone is adjusted with a trial and error procedure, using a 2D forward modeling method based on a Raleigh-Fourier approach. The response of two adobe walls with a tile deposit in between is calculated and the resulting model presents a good agreement with the model obtained from the inversion of the geoelectrical data. Also the synthetic response of two adobe walls with no tile deposit is calculated and we find that this response is different and  the data cannot be adjusted with this model. We conclude then that the EMI method is appropriate to discriminate different types of resistive structures and that it can be used to obtain quantitative information when 2D modeling is performed.