一种改进的地震波初至走时逆风差分算法

自Vidale提出有限差分解程函方程的初至波走时计算方法以来，由于最初算法的局限性，又有许多作者提出了改进的算法，主要包括基于波阵面的扩展以及逆风差分算法，这些改进的算法在井间走时计算方面是有效的。但是，在进行初至波走时层析成像研究的过程中发现，利用以往的算法对震源与检波点位于地表的模型进行计算的时候，如果存在速度差异较大的水平分界面时，在速度界面附近的走时计算结果会出现较大的误差，从而影响成像的精度。提出了一种改进的地震波走时计算的逆风差分算法，通过考虑首波和散射波的走时，能有效地减小速度值差异较大的近地表地质模型的走时计算误差，准确地描述速度界面上折射波的滑行描述，特别适用于近地表层析成像及地震勘探中的静校正问题。

Improved upwind finit-difference algorithm for computation of seismic first arrival traveltime

Many wavefront expanding and upwind algorithms have been proposed to improve traveltime computation since the finite difference solution of eikonal equation was initially proposed by Vidale.They have been demonstrated effective in crosswell transmission tomography.However,it was found that these methods failed to give an accurate representation for seismic traveltime along the interface between different velocity layers when it is applied to near-surface velocity model.In order to solve this problem,an improved algorithm is presented in the paper.Results from model data show that the method can diminish traveltime error in near surface model with great difference in slowness and describe accurately seismic sliding along the interface of the velocity layers.