【摘要】 地震数值计算表明:地震速度模型出现误差,对时间偏移和深度偏移有不同的影响,且深度偏移结果的误差往往大于时间偏移的误差,影响了深度偏移方法的广泛应用。根本原因在于时间偏移使用的是均方根速度,而深度偏移使用的是层速度,因此在速度模型相同的情况下,层速度的变化远大于均方根速度的变化。地震数值模拟分析同时说明,深度偏移结果的误差还取决于地下介质的结构和岩性。当界面二边速度差异比较大时,速度摄动值δ引起深度偏移结果的误差,远大于界面二边速度平缓变化的情况。深度成像的误差等于速度摄动值δ和界面二边速度对比度vi+1/vi的乘积。更多还原

【Abstract】 Seismic numerical calculation in this paper shows that effects of velocity model errors on seismic time and depth migrations are different.The depth migration is more sensitive to migration velocity errors than time migration due to the different kinds of velocities used.As we know the RMS velocities are used in time migration and interval velocities are used in depth migration and the variations of RMS velocities are much smoother than the ones of interval velocities under same velocity models.This is the main reason for those two kinds of migrations with different imaging errors in the same velocity perturbation δ.The seismic numerical modeling shows that depth migration errors are also dependent on the structure and lithology of subsurface,which means the relative errors in depth imaging caused by velocity perturbation will be larger in the media with strong velocity contrasts than the cases with smooth velocity contrasts.The depth imaging error is equal to product of velocity perturbation δ and velocity contrast vi+1/vi in a subsurface.更多还原