Inversão Sísmica Em Três Dimensões A Partir De Dados De Reflexão Sísmica Por Algoritmos Genéticos Híbridos

Abstract

The objective of the present work is to investigate a method to help in the quantification of seismic characteristics underground. The two-dimensional seismic model of reflection employs the equation Normal Move Out (NMO) to calculate the travel times of P waves reflected on inclined and isotropic layers. This equation uses the root mean square velocity as a representative value of the joined layers velocities. At the inversion process, for multiple layers, the root mean square velocities are the main problem to estimate the layer velocities. Consequently, to solve that problem, the proposed method estimates sequentially the parameters of the seismic model using travel times and the Hybrid Genetic Algorithms (Genetic algorithm and the Nelder Mead Simplex algorithm). The travel times are synthetic and the estimation of parameters is treated as a minimization problem. With proposed method was obtained high grade of accurate, and the reduction of 85.23% of computing time when the method uses only Genetic Algorithms. For decreasing the complexity and the delay to generate the models in three dimensions is proposed the construction of a three-dimensional seismic model formed with two-dimensional models, under every rectangular cell of the mesh of receptors of the seismic survey, for curved isotropic layers with soft variations in the gradient and without discontinuities. The twodimensional models form polygons that represent the surfaces of interfaces that are designed under the rectangles of the surface or soil. Two sets of polygonal surfaces are generated to help at the geometric localization of layers.