Geoacta

Comparison of seismic noise signal processing methodologies for data recorded in the Paraná, Chaco-Paraná and Pantanal basins region

2023-10-04T22:54:15+00:00

The extraction of the Green's function from the cross-correlation of seismic noise data between pairs of stations is achieved because seismic noise is recorded at both stations, without the need for an earthquake to occur. The stacking of cross-correlations over a long period of time improves the waveforms and contributes to reduce the difficulties generated by the irregular distribution of noise sources. In this study we compare two methodologies for the cross-correlation determination, the Geometrically Normalized Cross-Correlation and the Phase Cross-Correlation, and two different procedures of stacking, the Linear Stack and the Phase-Weighted Stack, applied to seismic noise data recorded in the region of the Paraná, Chaco-Paraná and Pantanal basins, in South America. The analysis of similarity based on the amount of days considered in the stack, allows us to define certain parameters of the preprocessing, such as the cut-off frequencies of the bandpass filter and the length of the records. Based on this analysis, we have concluded that the Phase Cross-Correlation methodology is the best option for these data, being one year of data enough to obtain the adequate stability in the results. Both procedures of stacking have produced similar results for these data.

Calculation of groundwater storage in the northern dune chain of the Villarino district from electrical resistivity tomographies

2023-10-05T04:40:18+00:00

In the northern sector of the Villarino district, in the southwest of the province of Buenos Aires, there is a chain of continental dunes. This chain of sands contains a phreatic aquifer, which carries water of good physicochemical quality and is the only source of water supply for the populations of the area. The present work aims to estimate the volume of groundwater storage in this aquifer, using electrical resistivity tomography (TRE), defining the saturated thickness of interest. Using this methodology, seven tomographies were carried out in different portions of the chain of sand dunes. The interpretation of the resulting images made it possible to identify the resistivity intervals correlated with the hydrogeological characteristics of the dune chain and the thickness saturated with fresh water in each area, in order to subsequently calculate the volume of groundwater storage in each sector. As a result, thicknesses of interest greater than those obtained in previous measurements were observed, thus calculating a volume of groundwater storage of 344 Hm³. This is considered the most appropriate estimate according to the available data. The methodology applied is of great use for the hydrogeological knowledge of the subsoil and provides data of interest for a more accurate calculation of groundwater storage, which is of great importance for the management and rational and sustainable exploitation of groundwater.

Evaluation of a 5 pillars baseline for MED equipment calibration

2023-10-09T02:58:25+00:00

This paper presents the implementation of a baseline for the calibration of electro-optical distance meters (MED) commonly used in engineering and surveying works. A baseline is made up of a series of fixed points aligned on the ground, and meets with a series of characteristics that allow determining the magnitudes of the systematic errors of a MED equipment together with their corresponding expressions of uncertainty (calibration parameters) from the observed distances. The distances between the points must be nominal values obtained with a higher precision equipment than those to be tested, they must also be traceable measurements. A baseline should be understood as a tool that makes it possible to generate observations of distances that constitute representative statistical samples of the measurements that are commonly carried out with the tested equipment.

This work covers the set of analyzes carried out on a baseline design, the most appropriate measurement procedure and the type of calculation adopted to achieve the results. In order to validate these proposals, experimental measurements were made with test equipment in a transitory baseline. To carry out these tests, equipment from the Argentinian German Geodetic Observatory (AGGO) was used, which complies with the technical specifications required to obtain the distances that were used as nominal values.

The implementation of a transitory baseline made it possible to develop the test on the test equipment, applying the developed procedures, and as a result its calibration parameters were obtained.

Geoelectric study in the town of Nogolí: A contribution to the understanding of the structure and hydrogeology in the western foothills of the Sierra de San Luis

2023-11-08T03:44:52+00:00

The following work, used the application of vertical electrical sounding (VES) with the Schlumberger symmetrical electrode array for the determination of the electrical properties of the subsoil in Nogolí town. With the information obtained in each VES, an integration and subsequent construction of apparent resistivity profiles (pseudo section), isopach maps of Quaternary and Neogene sediments, igneous-metamorphic basement and the unconfined aquifer of the locality was carried out. The use of the geoelectric method in different points of interest, allowed us to understand the behavior of the western edge of the Sierras de San Luis in a geological context of contractional dynamics, which gave rise to a prograding deformation towards the center of basin (piedmont forelands). The hydrogeological conditions of the locality are affected by the structuring of the sector that produces the discontinuity of the aquifer in the footwall located to the west of the detected faults, also generating a north and south bifurcation.