复杂地表条件静校正中的3D表层速度层析反演研究

针对复杂山地的静校正问题，研究了利用基于初至时间的3D表层速度层析反演技术。给出了反演方法的基本原理，即采用基于最短旅行时原理的射线路径追踪法计算初至波的路径和旅行时，采用同时迭代重建技术（SIRT）计算速度修正量．修改速度模型。最终的速度模型通过正演和反演多次迭代获得，不依赖于初始模型。用一个速度变化复杂的卵论模型对该方法进行了试算，结果表明．该方法很好地重建了横向剧烈变化的3D速度结构。对南方某山地3D资料处理结果表明，用该方法可以获得可靠的3D近地表速度模型和静校正量。

3-D tomographic imaging of nearsurface velocity for complex near surface statics calculation

Aimed to an approach that derives the 3-D nearsurface velocities,on which the reasonable field static values for complex nearsurface can be calculated, from the arrival time of first break by using tomography technology. The approach is two steps included the forward and inversion. Shortest Path Ray Tracing is used in the forward step to calculate first break time as well as ray path and SIRT (Simultaneous Iterative Reconstruction Technology) in the inversion step to determine the adjustment to previous near-surface velocity model. A new velocity model is constructed by adding the adjustment to previous one. The final velocity model will be reached by iteration of the two steps and is independent of initial model. The example of theoretical model, containing highly variable near-surface velocities in 3 directions, shows that the sharp lateral variations of 3-D near-surface velocities can be reconstructed appropriately by the approach.Results demonstrate that the reliable 3-D near-surface velocities and also static values can be achieved by using the approach from the south China mountainous area.