Terra - feições ilustradas

Sem resumo no origina

ANALYSIS OF SURFACE WAVES RECORDED AT A MASS MOVEMENT IN BRASÍLIA, BRAZIL: AN IMPLICATION IN HAZARD MITIGATION

Ever increasing urbanization over the thick and less cohesive soil of the Federal District (DF), Brazil has increased area's vulnerability to natural hazards, especially the soil erosion and mass movement. This preliminarily study applied noise based geophysical techniques like power spectral density (PSD), horizontal to vertical spectral ratio (HVSR), multichannel analysis of surface waves (MASW) and noise interferometry to a mass movement in Brasilia for the understating of geodynamic processes working in the background of these hazards. Here obtained results show a uniform stratigraphic peak at 2 Hz observed on all HVSR curves, a four layered shear wave section was obtained by MASW. Dispersion curve (frequency vs phase velocity) shows first and second fundamental modes at frequencies of 5 and 25 Hz, respectively. Noise correlograms show time delay larger than +- 0.5 sec on the waveforms of ZR (vertical-radial) component, mainly in acausal part. Relative velocity changes calculated by stretching technique show anomalous trends in response to rainfall events. Follow research will focus on the detection of possible changes in noise records within mass movement mainly related to natural triggering factors (rainfall and river erosion) under more controlled data conditions

Georadar Application for Site Characterization of a Waste Disposal on Quartzite Soil

Abstract Poorly managed disposal of solid waste on permeable soil may have serious environmental concerns which can greatly benefit from quick site investigation using non-invasive and cost-effective methods. Therefore, the present research examines the efficiency and agility of ground penetrating radar (GPR) in dumpsite characterization. A case study was conducted on the Alto Paraíso de Goiás dumpsite (Brazil), where the natural ground is composed of coarse-grained quartzite soil. The GPR data were acquired with 200 MHz shielded antennas, at a sampling interval of 0.05 m, covering the dumpsite and its adjoining. A commonly adopted processing workflow, and as a result, four predominant reflection patterns and a discontinuous surface were identified and interpreted in terms of site stratigraphy, contaminant pathways, and plume geometry. The GPR interpretation was enhanced by incorporating the lithological information from nearby monitoring wells. The study shows the potential of applying the GPR method as an effective geophysical characterization tool for waste disposal sites on quartzite

Benefits of the successive GPM based satellite precipitation estimates IMERG–V03, –V04, –V05 and GSMaP–V06, –V07 over diverse geomorphic and meteorological regions of Pakistan

Launched in 2014, the Global Precipitation Measurement (GPM) mission aimed at ensuring the continuity with the Tropical Rainfall Measuring Mission (TRMM) launched in 1997 that has provided unprecedented accuracy in Satellite Precipitation Estimates (SPEs) on the near-global scale. Since then, various SPE versions have been successively made available from the GPM mission. The present study assesses the potential benefits of the successive GPM based SPEs product versions that include the Integrated Multi–Satellite Retrievals for GPM (IMERG) version 3 to 5 (–v03, –v04, –v05) and the Global Satellite Mapping of Precipitation (GSMaP) version 6 to 7 (–v06, –v07). Additionally, the most effective TRMM based SPEs products are also considered to provide a first insight into the GPM effectiveness in ensuring TRMM continuity. The analysis is conducted over different geomorphic and meteorological regions of Pakistan while using 88 precipitations gauges as the reference. Results show a clear enhancement in precipitation estimates that were derived from the very last IMERG–v05 in comparison to its two previous versions IMERG–v03 and –v04. Interestingly, based on the considered statistical metrics, IMERG–v03 provides more consistent precipitation estimate than IMERG–v04, which should be considered as a transition IMERG version. As expected, GSMaP–v07 precipitation estimates are more accurate than the previous GSMaP–v06. However, the enhancement from the old to the new version is very low. More generally, the transition from TRMM to GPM is successful with an overall better performance of GPM based SPEs than TRMM ones. Finally, all of the considered SPEs have presented a strong spatial variability in terms of accuracy with none of them outperforming the others, for all of the gauges locations over the considered regions

Typological analysis of slidequakes emitted from landslides : experiments on an expander body pile and Sobradinho landslide (Brasilia, Brazil)

Reactivation of a landslide is usually accompanied by microseismic signals emitted from the deforming soil mass. The reproduction of similar signals in a physical model test conducted under control conditions can allow researchers to explore and test such complicated signals to improve the prediction of full-scale failure. The present study investigates the similarity between the slidequakes (microseismicity) naturally emitted from an existing colluvial landslide (Sobradinho, Brazil) in response to rainfalls and the emissions generated by a pullout test of an expander body (EB) pile in tropical soil under controlled conditions. The microseismic signals emitted from both experimental sites (i.e. the landslide and the EB pile test) were recorded and compared. Data were acquired by mini-arrays of four short-period seismometers. For the signal nomenclature, a typological scheme was adopted, in which sonograms/spectral contents of the signals were used. As a result, short duration microseismic signals were observed during the pullout test. In contrast, at the Sobradinho landslide, the testing detected signals of different characteristics whose source mechanisms have remained ambiguous, mainly because of the short duration of the data campaigns. However, at the landslide, propagating events were observed that might be attributed to the energies generated by the river bedload during the heavy rains. The present study offers some insight into the pre-collapse dynamic behavior of unstable slopes in clayey formations

Terra - feições ilustradas

Sem resumo no origina

DISTRIBUIÇÃO ESPACIAL DE DEPRESSÕES NA BACIA DO ALTO RIO PRETO (GO, DF, MG) E SUAS RELAÇÕES COM CONTROLES GEOLÓGICOS E PEDOGEOMORFOLÓGICOS

O presente estudo tratou das feições doliniformes na bacia do alto rio Preto. De um total de 177 feições identificadas, a maioria está próxima ou conectada à drenagem, sendo menos circulares que outras identificadas como isoladas. Tais feições possuem agrupamentos nítidos e sua distribuição indica que são controladas por falhas associadas a dobras da Faixa de Dobramentos Brasília, diante da comparação de seus eixos de orientação com alinhamentos geológicos. Foi observado que 90% das depressões se assentam sobre as rochas carbonáticas do Grupo Bambuí.</p