Monitoring of water table fluctuations of the Barreiras Aquifer using seismic interferometry of noise, Region Barreira do Inferno Launch Center
water table, interferometry, passive monitoring, Barreiras Aquifer-RN (Brazil), seismic noise
The fluctuation of the water table is associated to climatological factors, structural processes and anthropogenic activities. The understanding of this hydrogeological variant is fundamental in the evaluation of the regulatory reserves, besides being important also in the prevention of damages to the existing terrestrial and underground infrastructure. The seismic noise wavefield can be used to monitor these structural changes. Through interferometry it is possible to recover the signals, which contain the structural response of the medium from cross-correlations of noise. Through interferometry it is possible to recover the signals that contain the structural response of the medium from cross-correlations of noise between two stations. In addition, autocorrelations of the noise wavefield recorded in a single station can also be used to monitor media changes. In this way, the present research proposed to use the signal interferometry tool in the recovery of the medium response as an alternative to the unconfined aquifer monitoring in sandstone formations. The preliminary analysis with data of 16 days, obtained by the station MGP installed in the hydrographic basin of the river Maxaranguape, indicate that with few hours of data it is possible to recover the empirical function of Green, especially for the case of the classic correlation. However, it was noteworthy to observe that the rainy periods affected the stability of the autocorrelograms, especially for bands of higher frequencies. This fact corroborates the need for more studies for the winter period, in view of the quantitative analysis of soil saturation and the influence of rainfall on the water table fluctuation. Thus, after the preliminary analysis and the literature review it was possible to find evidence on the applicability of the technique of seismic interferometry in the monitoring of seasonal fluctuation of the water table.