The Joint Inversion Of The P-wave First-arrival Times And Rayleigh-wave Dispersion Curves

In recent years,shallow seismic exploration has increasingly attracted the interest of geophysicists.Near-surface model parameter can provide initial static corrections for field seismic data which obtained through shallow seismic exploration.It can provide the high quality seismic data for the processing.There are two commonly used near-surface velocity modeling methods---first-arrival wave travel-time inversion and surface wave dispersion curve inversion.Each method has its own advantages and limitations.In this paper,there are four main researching aspects as follows:(1)At first,take the inversion of the first-arrival wave travel-time and the model was trial-calculated.Through the conclusion analysis,it was concluded that the method requires the velocity of near-surface model to increase with depth.And the SNR of first-arrival wave data should be higher.(2)Secondly,the near-surface model inversion is applied to the surface wave dispersion curve.Through the model trial-calculated,it was concluded that the inversion accuracy will decline with the depth of the formation,mainly due to the sharp decline in surface wave energy as the depth declines.(3)Finally,the joint surface inversion method was used to model the near surface velocity.Rayleigh surface wave dispersion curves and first-arrival wave travel-time are jointly inverted using the least-squares algorithm.The relationship between the P-wave velocity and the S-wave velocity in the Poisson's ratio is used to relate these two geophysical data.The data columns are linked and constrained by the covariance matrix,so that the two seismic wave velocities are linked and constrained in the inversion process to reduce the ambiguity of inversion.Through the inversion of models,it is verified that the method of joint inversion can effectively avoid the limitation of single inversion and effectively improve the accuracy of near-surface velocity modeling.And through the error analysis of the inversion results,it is concluded that this inversion method is especially effective for improving the P-wave velocity inversion results when the first arrival wave data contain noise.