基于应力偏量的横波纯应力逆时偏移成像方法

基于弹性波解耦延拓方程的波场分离方法不仅可以得到解耦的纵、横波质点振动速度场，还可以获得纵、横波应力场.针对横波纯应力场在利用单一分量成像时不具有明确物理意义的问题，本文将应力偏张量引入到横波应力场中，基于应力偏量第二不变量构建得到横波应力不变量并将其用于应力场的逆时偏移成像中，获得了可完整表征横波应力场的成像结果.模型试算表明，本文构建的横波应力不变量可以有效利用横波应力张量中的波场信息，并得到准确的弹性逆时偏移成像结果.

A reverse time migration method for shear wave pure stress based on stress partial tensor

Both the decoupled P-wave and S-wave particle velocity field and stress field can be obtained through wavefield separation. To investigate the physical meanings of S-wave pure stress field in single component imaging, stress partial tensor is introduced to S-wave pure stress field in this paper. Based on the second invariant of stress partial tensor, S-wave stress invariant is established and applied to stress field reverse time migration, from which the imaging results can completely characterize S-wave stress field. Numerical tests demonstrate that the wave-field information of S-wave stress tensor can be effectively utilized via the established S-wave stress invariant, which contributes to accurate elastic wavefield imaging.