ABSTRACT

  • The use of unsupervised machine learning methods such as K-means, Hierarchical Agglomerative Clustering, and Self-organizing maps is constantly increasing in seismic interpretation. Regarding unsupervised methods, the K-means technique is one of the simplest ways to cluster seismic facies, although it presents neither a structure between the generated labels nor a measure of similarity when considering their order. To solve this drawback, we propose two automated label organization techniques that use principal component analysis (PCA) to organize those obtained from the algorithm, preserving some degree of similarity. To demonstrate the effectiveness of these methods, we interpreted two stratigraphic... Leia Mais

  • Wave-seabed interaction is known to be a fundamental cause of sediment instability and entrainment. Observations of burial for surrogate munitions were made with a high frequency, sector scanning sonar acquiring acoustic images of the seabed every 12 min during a storm event in May 2013 in the northern Gulf of Mexico offshore of Panama City Beach, FL. Surrogate munitions burial depth was verified by divers. Driven by time series of pressure observed near the seabed, an existing poro-elastic wave-sediment interaction model in combination with a sediment failure criterion due to liquefaction (loss of vertical effective stress) was used to correctly estimate depth and timing of burial. We introduce the concept of... Leia Mais

  • The transition zone between the Archean blocks, Jequié and Itabuna-Salvador-Curaçá, in the county of Laje, Bahia, Brazil, is potentially important for iron ore deposits of economic interest. This research investigates one of the eighteen anomalies defined by a previous integrated interpretation of geological and airborne gamma ray spectrometry and magnetic data in this transition zone. Its choice resulted from being located in an area with intense transcurrent shear and from the occurrence of pebbles rich in magnetite. Because of paucity of surface geological information, a ground-based geophysical survey added valuable information for the definition of a drilling program in the area... Leia Mais

  • Density differences among subsurface rocks cause variations in the gravitational field of Earth, which is known as gravity anomaly. Interpretation of these gravity anomalies allows assessment of the probable depth and shape of the causative body. For several decades, gravity data were acquired on the surface, but after the scientific and technological advances of the last decades, geopotential models were developed, including gravitational observations on a global scale through space satellite missions. This paper investigated the Moho structure in the region of Recôncavo-Tucano-Jatobá rift-basin system based on the information of the terrestrial gravity field from the EIGEN-6C4 geopotential model. The... Leia Mais

  • Normal moveout (NMO) velocity is used in seismic data processing to correct the data from the moveout effect. This velocity depends on the medium above the reflector and it is estimated from the adjustment of a hyperbolic function that approximates the reflection time. This approximation is reasonable for media formed by isotropic layers. For deeper exploration targets, which effectively behave as anisotropic media, the NMO velocity estimate from the hyperbolic approximation becomes imprecise. One possibility is the use of non-hyperbolic approximations for the reflection time and deeming the medium to be anisotropic. However, these approximations make the NMO velocity estimation a more complex problem... Leia Mais

  • A análise geoquímica foi realizada na porção centro-sul do estado da Bahia, no semiárido baiano, onde afloram o Complexo Paramirim, Unidade Boquira, Granito Boquira, Granito Veredinha, Serra do Espinhaço, Coberturas detríticas e Depósitos aluvionares. A Unidade Boquira é conhecida pelas mineralizações chumbo-zincíferas. Nessa unidade operou a mina Boquira, considerada a maior mina de chumbo e zinco do Brasil até ser subitamente abandonada, o que deixou expressivo passivo ambiental de metais tóxicos como chumbo, zinco, prata, bário, cobre, cromo e níquel. Para caracterizar a água subterrânea utilizaram-se 16 parâmetros físico-químicos de 24 poços, obtidos por meio da Companhia de Engenharia Hídrica e de... Leia Mais

  • A análise de definições sobre a expressão sensoriamento remota permite constatar a existência de divergências e convergências com a fotogrametria, causando confusões no seu entendimento e até na sua aplicação. Os autores apresentam suas argumentações e compreensão sobre esta temática, afim de minimizar este dilema com base em uma retrospectiva histórica, com fatos que favoreceram o desenvolvimento da fotografia, fotogrametria (estabelecendo níveis de evolução), satélites artificiais e por último, das aeronaves remotamente pilotadas. Neste contexto, o presente trabalho traz esta contextualização, expondo os avanços tecnológicos e personagens que contribuíram para o seu sucesso. Por fim, com base nas... Leia Mais

  • Abstract: A set of open-source routines capable of identifying possible oil-like spills based on two random forest classifiers were developed and tested with a Sentinel-1 SAR image dataset. The first random forest model is an ocean SAR image classifier where the labeling inputs were oil spills, biological films, rain cells, low wind regions, clean sea surface, ships, and terrain. The second one was a SAR image oil detector named “Radar Image Oil Spill Seeker (RIOSS)”, which classified oil-like targets. An optimized feature space to serve as input to such classification models, both in terms of variance and computational efficiency, was developed. It involved an extensive search from 42... Leia Mais

  • Abstract: 3D Reverse-time migration (RTM) is a powerful technique for imaging complex geologic structures. This approach requires a significant computational effort, demanding a high amount of memory for storing the source's wavefields, consequently leading to a high cost to perform the imaging condition. Thus, this work aims to reduce these problems by introducing a dynamic approach (DA) that considers the sparsity of the wavefield in the first periods of propagation. The RTM combined with the DA (RTM-DA) approximates the computational domain to the propagation domain, which is the region delimited by the wavefront. In practical terms, the computational domain expands together with... Leia Mais

  • The representation of compressional seismic waves velocity fields from geological models through numerical parameters has a strong geophysical importance, because, it makes possible to quantify such qualitative models, allowing its mathematical manipulation. In this way, the parameterization by Haar wavelet series may be seen as an attractive alternative. The pyramid algorithm is used to obtain a multi-scale wavelet series representation of such models. It is applied filters that assure an optimized parameterization of models with important parameter reduction without significative loss in the model representation. It is accomplished the parameterization of velocity field models... Leia Mais