全走时反演及其应用

波动方程速度建模方法是利用地震数据或成像道集中的旅行时信息或运动学特征自动反演出背景速度模型,但是已有方法普遍面临一个严重的问题,即反演过程无法避免受振幅信息的影响。为此,提出了一种基于波动方程的旅行时反演方法,称之为全走时(即完全依赖于走时信息)反演,从地震数据中自动估计出运动学意义上正确的速度模型,其核心思想是使反演完全依赖于走时信息,从而防止反演受到振幅信息的干扰。基于速度扰动只产生旅行时变化这一假设,介绍了数据域和成像域两种全走时反演方法,分别对应透射波和反射波走时反演。全走时反演不需要准确的初始速度模型和地震数据中的低频信息。理论模型和实际资料测试结果表明,全走时反演在常速度初始模型的情况下也能得到令人满意的反演结果。

Many previously published wave-equation based methods,which attempt to automatically invert traveltime or kinematic information in seismic data or migrated gathers for smooth velocities,suffer a common and severe problem,that is the inversion are involuntarily and unconsciously hijacked by amplitude information.To overcome this problem,we present a new wave-equation based traveltime inversion methodology,referred to as full traveltime inversion (FTI),to automatically estimate a kinematically accurate velocity model from seismic data.The key idea of FTI is to make the inversion fully dependent on traveltime information,thus prevent amplitude interferenceduring the inversion.Under the assumption that velocity perturbations cause only traveltime changes,we derive the FTI method in both data domain and image domain which are applicable to transmitted arrivals and reflected waves,respectively.FTI does not require an accurate initial velocity model or the low frequencyseismicdata.Synthetic and field data tests demonstrate that FTI produces satisfactory inversion results,even using constant velocity models as initials.