弹性波各向异性高斯束逆时偏移

Elastic reverse time migration with Gaussian beams in anisotropic media

弹性波高斯束逆时偏移是一种兼具计算效率和成像精度的多分量地震成像算法,具有面向目标成像的能力,但目前研究主要集中在声波各向同性、各向异性和弹性波各向同性介质,有关弹性波各向异性介质的研究较少。首先,基于地震波矢量特性,在震源点和检波点分别采用P波和S波进行射线追踪,发展了一种基于相速度的各向异性弹性波射线追踪算法,该算法不仅具有较高的计算效率,而且能消除求取地下介质各向异性参数时的不确定性;然后,通过弹性波动力学高斯束表征的格林函数来实现波场正反向延拓;最后,对正反向延拓波场进行互相关获取成像值,实现弹性波各向异性高斯束逆时偏移。VTI复杂构造模型和TTI断层模型数据的应用表明该方法能够对各向异性构造准确地成像,与传统的基于弹性参数的算法相比,其算法的计算效率更高。

The elastic wave reverse time migration with Gaussian beams is a multi-component seismic imaging algorithm with both computational efficiency and imaging accuracy,which can be used for target-oriented imaging.The current research mainly focuses on acoustic isotropic,anisotropic,and elastic-wave isotropic media.Relatively few studies have been conducted on elastic-wave anisotropic media.In this study,relying on the vector characteristics of seismic waves,the P-wave and S-wave at the shot points and receiver points,respectively,were adopted for ray tracing.Then,an elastic-wave anisotropic ray-tracing algorithm was developed based on the phase velocity.This algorithm not only has a high calculation efficiency but can also eliminate uncertainty when calculating the weak anisotropic parameters of subsurface media.Then,the Green function characterized by the elastic wave dynamic Gaussian beam was used to realize the forward and backward continuation of elastic wave fields.Finally,cross-correlation of forward and backward wave fields was carried out to obtain the imaging results,and thus,an elastic wave reverse time migration with Gaussian beams for anisotropic media was realized.The imaging performance of the proposed method were verified using the VTI complex structure model and the TTI fault model.Compared with the traditional algorithm based on elastic parameters,the computational efficiency of the proposed algorithm is higher.