Abstract：Normal Moveout (NMO) is one of key steps in seismic data processing,its precision has direct impact on whether the interference wave can be effectively suppressed by horizontal stacking.NMO is also a tool used for velocity analysis.Ordinary NMO processing uses Dix hyperbolic formula to align event under two preconditions:① it's in isotropic layered medium;② it's for middle or near offset receiver spread.But the long offset receiver spread usually is adopted when explored geological targets is beneath a high velocity stratum,so that the useful reflection beneath the high velocity stratum can be received.Under the circumstances,using Dix formula for NMO correction of long offset data can bring large errors,so higher order polynomial fitting must be adopted.The paper analyzed different NMO methods for long offset seismic data by forward calculating horizontal layered medium model,considering that there is no such thing for NMO correction of long offset seismic data as that the higher the used order in polynomial fitting is,the better the precision of NMO correction is and that shifted hyperbola is not optimum everywhere.In a condition of without considering influence of anisotropic medium temporarily,the coefficient of high order terms in polynomial is key factor having impact on NMO correction of long offset seismic data, determining what NMO method should be used in practical processing of long offset seismic data.
