Aproximações hiperbólicas dos tempos de trânsito de raios paraxiais a um raio central refletido e difratado

Abstract

The simulation of a zero-offset seismic (ZO) section from multicoverage, through of stack, is a very used method of seismic reflection imaging, that reduce the amount of data and is aimed to improve the signal/noise ratio. Based on hyperbolic traveltime approximation depending on three kinematic attributes, recently, it was developed a new method to simulate zero-offset (ZO) sections called common reflection surface stack (CRS) method. Also, following this new concept of seismic imaging it was introduzed a method to simulate common-offset (CO) sections from multicoverage data by using a paraxial traveltime approximation for paraxial rays in the vicinity of the finite-offset centra ray. This new traveltime approximation depend on five kinematic attributes. In this work, from the hyperbolic paraxial traveltime approximation with finite-offset central ray, we derive a new formula of traveltime approximation by using the diffraction point condition, reducing the original formula to four parameters. For both approximations, that´s for reflection and diffractions, we show the finite-offset FO-CRS stack operators. We, also obtain these formulas to the four seismic configurations (common-shot (CS), common-receiver (CR), common-midpoint (CMP) and common-offset (CO)). To analise behaviour FO-CRS stack, when this is perturbed, we debatable the sensibility with respect to each one the five parameters (K1, K2, K3, βS and βG). This sensibility analysis was perfomed in two ways: Sensibility through the disturbance of each parameter visualized in the stacking surfaces FO-CRS- and FO-CDS, and the first derivative of the traveltimes FO-CRS and FO-CDS. After realize the sensibility analysis, we utility a new condition, K2 = 0 and therefore, we obtained a new approximation, now depend on three parameters. Using that hyperbolic traveltime approximations (in function of five, four and three parameters), we propose an algorithm multicoverage seismic reflection data. Finally, is presented a studed of Fresnel zone, to delimit the aperture of FO-CRS stacking surface.