论文部分内容阅读
为了解决海底起伏变化对地震波场的影响问题,本文提出将(x-z)域中的曲网格映射成(ξ,η)域中的矩形网格,推导出(ξ,η)域中的二维标量声波方程,根据推导出来的波动方程采用逆时有限差分法将海面上采集到的地震波场在(ξ,η)域中向下延拓至海底面,延拓时采用海水的速度,然后采用顺时有限差分法将延拓后的地震波场再反延拓到海面上,延拓时采用海底面以下地层的速度,从而消除了海底起伏带来的负面影响。模型及实际地震资料的计算分析表明该方法不但能够校正由于海底起伏所引起的海底面下地层反射波场的不连续性还能够校正由于海底起伏所引起的地震波的动力学特征的变化。对延拓前后的地震波场进行速度反演,延拓后反演的地层速度比延拓前反演的地层速度的精度提高很多,延拓前后地震波场的叠加剖面对比表明该延拓方法能够明显提高地震波场的成像质量。
In order to solve the problem that seafloor fluctuation affects the seismic wavefield, this paper proposes to map the meshes in the (xz) domain into a rectangular grid in the (ξ, η) domain and deduce the two-dimensional Scalar sound wave equation, according to the derivation of the wave equation using inverse time-difference method to the seismic wave field collected on the sea surface in the (ξ, η) domain extends down to the sea floor, the extension of seawater speed, and then use The time-dependent finite difference method extends the continuation of the seismic wavefield back to the sea surface, and uses the velocity of the formation below the seafloor when it is extended to eliminate the negative impact caused by the seafloor fluctuation. The calculation and analysis of the model and the actual seismic data show that the proposed method can not only correct the discontinuity of reflected wave field in the sub-surface seafloor caused by seafloor fluctuation, but also correct the change of dynamic characteristics of the seismic wave caused by seafloor fluctuation. The velocity inversion of the seismic wavefield before and after extension is much more than that of the stratum inversion before extension, and the comparison of the superimposed sections of the seismic wavefield before and after extension shows that the continuation method can be obviously improved Seismic wavefield imaging quality.