Navegando por Autor "FERNANDES, Lindemberg Lima"

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Acesso aberto (Open Access)
Modelagem sísmica por diferenças finitas em meios bidimensionais com difratores
(Universidade Federal do Pará, 2000-09-14) FERNANDES, Lindemberg Lima; CRUZ, João Carlos Ribeiro; http://lattes.cnpq.br/8498743497664023
The subject of this work is the seismic modeling in medium with strong discontinuities in physical properties with enphasis in diffractions events. This research intend to contribute for a better comprehension and control of seismic modeling in complex medium. According to various authors, the Amazon Basin is formed by sedimentary rocks deposited since the Ordovician to the present, reaching depth up to 5 Km. The bodies of basalt between the paleozoic sediments are arranged as basaltic layers reaching thickness of hundred meters, which add to 90,000 km3. The ocurrence of these structures is responsible for the existence of multiple reflections during the propagation of the seismic waves, which makes impossible a better imaging of horizons located bellow the basaltic layers An accoustic velocity model was used to demonstrate this geological situation. The seismograms were calculated with a program of finite-difference with a fourth order aproximation of the acoustic wave equation in space and time. The aplication of the finite-difference method for modeling the propagation of the seismic waves has improved the understanding of the wave propagation in significant heterogeneous medium and achieves a good resolution in the interpretation of seismic reflection events in areas of interest As a result of numerical experiments accomplished in a complex geological medium a significant influence due to multiple reflection observed in a high velocity layer causing an increase in a loss of energy that made the data more dificult to analise. Because of this problem I advise the integration of the data from both surface and wells, to achieve a better imaging below the basaltic layer.
Acesso aberto (Open Access)
Modelagem sísmica via métodos das diferenças finitas: caso da bacia do Amazonas
(Instituto Nacional de Pesquisas da Amazônia, 2009-03) FERNANDES, Lindemberg Lima; CRUZ, João Carlos Ribeiro; BLANCO, Claudio José Cavalcante; BARP, Ana Rosa Baganha
This paper discusses the seismic modeling in medium with strong discontinuities in its physical properties. The approach takes in consideration the existences diffractions and multiple reflections in the analyzed medium, which, at that case, is the Amazon Basin. The stability and boundary conditions of modeling were analyzed by the method of the finite differences. Sedimentary rocks deposited since the Ordovician to the present, reaching depth up to 5 Km. The bodies of diabasic between the paleozoic sediments are layers reaching thickness of hundred meters, which add to 90.000 km3, form the geology of the Amazon Basin. The occurrence of these structures is responsible for multiple reflections during the propagation of the seismic waves, which become impossible a better imaging of horizons located bellow the layers. The representation this geological situation was performed an (synthetic) acoustic velocity model. The numerical discretization scheme is based in a fourth order approximation of the acoustic wave equation in space and time The understanding of the wave propagation heterogeneous medium has improved for the application of the finite difference method. The method achieves a good resolution in the interpretation of seismic reflection events. The numerical results discusses in this paper have allowed to observed the influence of the multiple reflection in a high velocity layer. It increase a loss of energy and difficult the interpretation of the target. For this reason the integration of surface data with the well data is recommended, with the objective to get one better image of the targets below of the diabasic layer.
Acesso aberto (Open Access)
Variação da precipitação por método de interpolação geoestatística
(2013-08) LOUREIRO, Glauber Epifanio; FERNANDES, Lindemberg Lima
This article analyses the variation of rainfall in the Tocantins-Araguaia hydrographic region in the last two decades, based upon the rain gauge stations of the ANA (Brazilian National Water Agency) HidroWeb database for the years 1983, 1993 and 2003. The information was systemized and treated with Hydrologic methods such as method of contour and interpolation for ordinary kriging. The treatment considered the consistency of the data, the density of the space distribution of the stations and the periods of study. The results demonstrated that the total volume of water precipitated annually did not change significantly in the 20 years analyzed. However, a significant variation occurred in its spatial distribution. By analyzing the isohyet it was shown that there is a displacement of the precipitation at Tocantins Baixo (TOB) of approximately 10% of the total precipitated volume. This displacement can be caused by global change, by anthropogenic activities or by regional natural phenomena. However, this paper does not explore possible causes of the displacement.