Limited-aperture CSP gathers used for AVO analysis

Content Provider	CiteSeerX
Author	Sun, Shuang Bancroft, John C.
Abstract	Traditionally amplitude variation with offset (AVO) is performed on CMP gathers on prestack data. However even if the subsurface has a mild structure, the common mid-point is no longer the common depth point. Thus AVO analysis after prestack migration is desired. The formation of the common-scatterpoint (CSP) gather provides a useful tool for such method. METHOD Cheops pyramid and Specular energy In seismic modelling an event may be constructed from a series of scatterpoints. Using a 2-D zero-offset forward model (x,t) the scatterpoints can be modelled by spreading energy on hyperbolas, the shape of which is defined by RMS velocity at the scatterpoint. Prestack modelling uses 3D surface of Cheops pyramid to recreate the reflection surface in (x,h,t). The prestack data (x,h,t) for a 2D line can be modelled by spreading energy in this volume with the shape of Cheops pyramid defined by RMS velocity at the scatterpoint. Modelling a horizontal reflector Figure 1 shows a horizontal hyperbolic cylinder that represents the hyperbolic moveout from a horizontal reflector in a constant velocity medium. Below the hyperbolic cylinder is a Cheops pyramid formed from one scatterpoint that lies on the horizontal reflector. The Cheops pyramid is tangental to the hyperbolic cylinder at constant x, or at the CMP gather that passes through the scatterpoint. The hyperbolic cylinder can be considered a reconstruction of many Cheops pyramids from many horizontal scatterpoints. In Figures 1a- b, the Cheops pyramid has had the time reduced by a small fraction, so that it will protrude through the hyperbolic cylinder, to illustrate the area of tangency. This area of tangency is visible in (b), surrounding the CMP gather located at the scatterpoint.
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Subject Keyword	Limited-aperture Csp Gather Amplitude Variation Rms Velocity Common Depth Point Many Horizontal Scatterpoints Cmp Gather Specular Energy Many Cheops Pyramid Hyperbolic Cylinder Method Cheops Pyramid Horizontal Hyperbolic Cylinder Prestack Migration Thus Avo Analysis Cheops Pyramid Constant Velocity Medium Horizontal Reflector Figure Reflection Surface Avo Analysis Prestack Data Common Mid-point Hyperbolic Moveout Horizontal Reflector Mild Structure 2-d Zero-offset Forward Model
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