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Seismometer component orientation is one of the most critical parameters for seismology, especially for methods that take wave field polarization effects into account, such as receiver functions, seismic anisotropy, surface wave dispersion and seismic tomography. Using P-wave particle motion combined with directional statistics, we estimated the orientation for 90 stations of the Brazilian Seismographic Network (RSBR), corresponding to 105 seismometers. The difference between the number of stations (90) and seismometers (105) is due to instrument replacement during station operation. We observed that 81 seismometers have an orientation of ±5° and 19 seismometers greater than ±5°. Only one seismometer has an orientation greater than 90° (BOAV station). ON and BR are the subnetworks of RSBR with the largest number of seismometers with orientation errors bigger than ±10° (6 for each one) and NB is the only subnetwork with no misoriented station. All the estimated orientations were close to the measured in the field, which is evidence that our approach is more accurate to detect misoriented stations than previous studies that analyzed the orientation of RSBR stations. The Watson's U2 statistical test indicated that the back azimuth deviations for Precambrian Basement and Phanerozoic Cover were significantly different, suggesting that the regional geology could affect back azimuth estimates. • P-wave particle motion was effective in detecting seismometer misorientation. • Directional statistics proved to be a suitable approach in back azimuth estimation. • Brazilian Seismographic Network has 14 stations with misoriented seismometers. • Stations deployed on Precambrian terrains tend to produce more accurate back azimuth estimates. [ABSTRACT FROM AUTHOR]

We present a P-wave structure for the sub-continental lithospheric mantle (SCLM) beneath the southern segment of the Amazonian Craton (Central Brazil Shield – CBS) using multiple-frequency tomography. Our model includes 469 seismic events recorded between 2009 and 2017 through 314 seismic stations distributed over South America. From these events, we obtained 20507 P and 12329 PKIKP cross-correlation delays in six frequency bands centered at 0.03, 0.06, 0.13, 0.25, 0.5 and 1 Hz. Despite the limited and heterogeneous resolution throughout the CBS, because of the difficulty in the installation of seismographic stations in areas of dense coverage of tropical forest, our tests show reasonable resolution for lithospheric domains with dimensions greater than 390 × 390 km in most of the study area. We recognized a good correlation between the P-wave anomalies and the tectonic domains defined previously based on geochronology and geological data. The surface projection of these anomalies and their margins are associated with clusters of important Au, Cu–Au and IOCG deposits, as well as diamond-bearing kimberlite intrusions, allowing relating deep structures with shallow features and showing a province-scale control in the distribution of mineral deposits and occurrences in the southern Amazonian craton. • Multiple-frequency seismic tomography in areas with low seismic stations coverage. • Relationship between deep structures and shallow features. • Correlation between P-wave anomalies and mineral deposits in the Amazonian Craton. [ABSTRACT FROM AUTHOR]

In forensic geophysical research, using controlled experiments assists forensic search practitioners in identifying optimal technique(s) and equipment configuration(s) in different burial scenarios. The objective of the research is to observe the geophysical response to different types of buried wrappings, taking into consideration the influence that the presence or absence of a decomposing body (pig carcass) in a lateritic soil in central-western Brazil can have. In this article, the GPR results are presented after a 15day burial period during the rainy season, and the results of Electrical resistivity tomography (ERT) after a burial period of 6 months during the dry season. The controlled site was built in the research area of the University of Brasília, in a region with soil, typical of the Brazilian savannah. 14 simulated clandestine graves of murder victims were constructed, in which seven pig carcasses were wrapped or covered by: soil (backfill), a plastic bag, a bed sheet, cement block, construction debris, a wooden coffin and hydrated lime, respectively a further seven burials, presenting only the wrappings acted as comparison (control burial). During the GPR survey a 400MHz frequency antenna was used. The resistivity surveys were carried out before and after the burial of the targets with dipole-dipole and Wenner-Schlumberger array configurations, with different spacing of electrodes (1.00 and 0.50m). The comparison between the various scenarios with and without pig carcasses revealed that good reflection events occurred mainly due to the wrappings and that pig carcasses attenuated the GPR signal. Electrical resistivity results showed that the Wenner-Schlumberger array presents a better resolution of the lateral boundaries of the burials, and the dipole-dipole array presents a better sensitivity to heterogeneity of the buried materials. The burials with the pig carcasses wrapped in the various materials presented better resistivity contrasts as opposed to the control burials. [ABSTRACT FROM AUTHOR]

The development and use of open-source software in geophysics over the last decade have grown considerably. However, there are few open-software alternatives for seismic methods and even fewer regarding seismic refraction data processing and inversion. We present Refrapy, an open-source package for seismic refraction data analysis written in Python, using some of the main libraries for scientific computing and geosciences. Divided into two main programs (Refrapick and Refrainv), it is possible to perform basic waveform processing, picking of first breaks, and inversion through time-terms analysis or traveltimes tomography, all with GUIs interaction. To evaluate and validate the products obtained using Refrapy, we analyzed sets of synthetic data and real field data. The calculated models recovered the geometry and velocities values of the actual synthetic models satisfactorily. The joint interpretation of the results obtained with both available inversion techniques permitted a more detailed interpretation. As for the analysis of real data, the results presented a compatible response compared to the model obtained by a well-established commercial software, satisfactorily representing the geological context interpreted initially. The software presented in this work is expected to contribute to the activities of researchers, practitioners, and students regarding the analysis of seismic refraction data as a free, open, and user-friendly alternative. • A new Python program based on GUIs for processing and inversion of seismic refraction data is presented. • Two inversion methods are offered: the time-term analysis and traveltimes tomography. • The use of the software is validated with the evaluation of velocity models obtained from synthetic and field data inversions. [ABSTRACT FROM AUTHOR]