The Study Of Inversed Regularity About Quality Factor In Absorbable Stratum

Seismic waves will attenuate because of the anelasticity of the media. Presently there are two interpretations for the attenuation. The one is elastic delay theory. It means under the durative function of external force, the internal structure of object changes; when external force disappears, the object cannot completely restore its original shape, and it has residual deformation. The exist of residual deformation consumes elastic energy, which makes amplitude of mechanical wave to take place attenuation during spreading process in the medium. The other is inner friction theory: It means to regard viscosity of medium as inner friction existing in solid interior, therefore during the distortion process of medium external force needs to over come friction and do work ,and transforms the energy of seismic wave to heat energy, which causes to attenuation of seismic wave. There is energy attenuation when seismic wave spreads in the medium, which inevitably affects the resolution of seismic survey. There are many methods to enhance the resolution, forward Q method is a commonly used method. The key to carry forward Q is the quality factor of stratum.During this research the author has read a mass of articles about seismic wave attenuation and inverse Q, knows the physical mechanism of attenuation,parameters of attenuation and main factor which influences attenuation of stratum, the author is also up to many of methods which geophysics summarize to inverse Q. On the foundation of above, the author bases on CMP gathers quality factor inverse method put forward by Changjun Zhang in 2002,applies it to different geological models, analyzes the effect using this method in different model parameters, expands application scope of this method. We can get the following conclusion:â‘ The precision of peak frequency directly affects accurate degree of inversed Q;â‘¡When there is low speed layer or high speed layer in the stratum, the inversed effect of low speed layer is better than high speed layer;â‘¢When there is a layer of strong attenuation, the thickness of this layer affects inversed result of the layers under it;â‘£When computing seismic wavelet using offset, I choose shallow layer data of near offset. The calculational result of model indicates: the method is suitable for many different geological model, and also can get well inversing effect .