Elastic Full Waveform Inversion(EFWI)makes full use of the dynamics and kinematic information of seismic waves to invert the P-and S-wave velocity models by minimizing the misfit function with high-resolutions.However,the conventional EFWI may suffer from severe cycle skipping without the low-frequency components in seismic data,which seriously affects the accuracy of P-and S-wave velocity parameters inversion.In this paper,we propose a Elastic Wave-Equation-Based Local-Scale Traveltime Inversion(ELTI)method to simultaneously recover the low-wavenumber components of the P-and S-wave velocity models by using the local-scale traveltime information of elastic full wavefields,which can effectively mitigate the cycle skipping problem of EFWI.The ELTI method makes full use of the local traveltime information of the elastic full wavefields,and is able to invert the P-and S-wave velocity parameters at the same time,which is a good solution to the defect of the conventional traveltime inversion method that can only obtain the P-wave velocity parameter.In addition,because the ELTI simultaneously utilizes the elastic full wavefields traveltime information,it can effectively improve the accuracy of the P-and S-wave velocity parameters inversion and provide a better initial velocity model for EFWI method.In this paper,first,the local-scale transformation is used to extract the local-scale traveltime information of the seismic elastic wave data,and then the local-scale traveltime difference between the observed and synthetic data is used to construct the ELTI misfit function;secondly,the gradient operator of the P-and S-wave velocity parameters corresponding to the ELTI misfit function is derived in detail by combining the chain rule and the adjoint-state method;finally,the P-and S-wave velocity models are updated simultaneously by combining the L-BFGS optimization algorithm.The results of the Marmousi model tests show that the elastic wave-equation-based local-scale traveltime inversion can better obtain the low-wavenumber components of the subsurface P-and S-wave velocity parameters,and thus mitigate the cycle skipping problem of EFWI.
Traveltime inversionLocal-scaleElastic waveFull waveform inversionMisfit function
万方数据
维普
