Partial angle domain anisotropy offset method based on TTI medium four-order travel-time equation

The invention discloses a partial angle domain anisotropy offset method based on a TTI medium four-order travel-time equation. The method comprises the steps that a TTI medium four-order time difference term is introduced in step-out time analysis, simplification is carried out with the help of horizontal reflector hypothesis of pre-stack time offset, and a concise travel-time inversion equation is further given out for achieving anisotropy parameter estimation; on this basis, common offset distance domain earthquake offset is expanded to a partial angle domain offset system, accurate description on seismic wave rays is achieved, and a fracture prediction level is improved. The method essentially improves the level of the anisotropy offset technology, more accurate and quantitative extraction and description on anisotropy characteristics (such as speed and amplitude) are achieved, fracture detection can be served better, and fracture inversion quality and accuracy can be improved. Azimuth information of seismic data can be fully utilized, sampling on azimuth is sufficient, the credibility of finally obtained information is improved, and the method is less influenced by noise.