Estimation Of Q And Inverse Q Filtering In Offset Direction For Prestack Seismic Data

Seismic wave propagation in a viscoelastic medium suffers from energy attenuation and velocity dispersion.For prestack seismic data,the earth absorption not only decreases the seismic resolution,but it also distorts the amplitude variation with offset(AVO).Quality factor Q is the most common one used to demonstrate the medium inherent absorption attribute.But the estimation of Q depends strongly on the quality of seismic data via traditional methods,which usually becomes unreliable under the influences of noise and spectral interference.Inverse Q filtering is a technique commonly used to remove absorption effects.However,its application often suffers from instability in the presence of noise.In order to improve the estimation accuracy of Q and enhance the stability of prestack seismic absorption compensation method,we firstly propose a lateral spectral ratio inversion method(LSRI)which uses the variation of seismic spectra in offset direction to calculate Q values.Then,we have developed a two-step scheme to remove the absorption effects.We decompose the seismic absorption into two independent components,namely,the offset and time components.The former is mainly responsible for seismic event variation in the offset direction,whereas the latter is mostly responsible for the decreased temporal resolution.On the assumptions of a horizontally stratified medium and a small incidence angle,we derive the mathematical expression of the effective dissipation factors for both components,and implement absorption compensation in the offset direction by an inversion scheme.Synthetic tests and real seismic data analysis demonstrate that the two-step process enhances the events uniformity and AVO analysis precision.