High-precision Joint Velocity Inversion With Seismic First-break And Reflection Travel-time

Seismic wave velocity is important during every procedure of seismic prospectingincluding collection, processing and explanation of seismic data. Therefore, how to preciselyget propagation velocity of seismic wave underground is one of the essential problems inseismic prospecting all the time.Seismic travel-time velocity inversion is one of inversion method which can inverseimportant information of underground medium such as structure, velocity distribution andelastic parameter by reconstructing algorithm with models using seismic travel-timeinformation collected. Seismic travel-time tomography is nonlinear inversion problem.Comprehensive velocity information can’t be obtained just through single wave inversion. Sovelocity-interface inversion with as more seismic information as possible has always been animportant way sought by geophysicists. First-break has high stability and obvious advantagesin velocity analysis of near surface and complex surface static move-out because it is easy todistinguish and trace while reflection wave can reflect deeper and finer structure andparameter distribution underground because of its strong energy with abundant undergroundinformation. Consequently, joint velocity-interface inversion with first-break and reflectiontravel-time is needed to provide more stable and precise velocity analysis for high-precisionseismic prospecting.This paper research the method of the forward modeling and joint velocity-interfaceinversion with first-break and reflection travel-time. Based on the forward and inversionmethod analysis, achieved the algorithm of travel time linear interpolation of the ray tracingmethod and LSQR method by programming.Obtained the following research achievement:1, based on the traditional travel time linearinterpolation of the ray tracing method, adopted the combination of column and line loops tocalculate travel-time of each grid node to eliminate the effect of inconsideration of rays comefrom all directions;2, combine the multi-stage calculation technology and ray tracing toachieve forward modeling of2D complex layered media reflected wave. Take theregularization to solve the mixed set problem of travel-time velocity inversion;3, Brought outa new algorithm of parameter weighted normalize in reflection travel-time velocity-interface inversion;4, To combine the first wave travel time speed inversion with reflected wave traveltime velocity-interface inversion acquired a quite good results.Verified the practicality and effectiveness of the methods in this paper by theoretical modeland real data testing and brought out methods and recommendations to further improve theaccuracy of inversion.