旅行时差值曲线方法在时间项反演中的应用

因对初至旅行时层数的确定和拐点拾取存存不确定性．导致时间项反演方法在近地表复杂区建立的速度模型精度不高，静校正效果不理想。对此提出了利刚旅行时差值曲线方法进行层数确定和拐点拾取。理论分析认为，运用旅行时差值曲线方法时，应尽餐选择相邻的激发点。通过对三层近地表速度模型进行射线追踪。得到初至旅行时，根据其旅行时曲线初步判定层数，再运用旅行时差值曲线进一步确定层数。观察时间项反演速度模型，其与近地表速度模型较接近，经计算反演速度模型与设计的近地表速度模型之间的均方根误差仅为0．95m，可见该方法可有效提高时间项反演的精度。

Application of Travel-time Difference Curve Method in Time-term Inversion

Time-term inversion is a simple and efficient method in constructing near-surface velocity model, and it employs observed first travel-times in modeling. In the common surveys, the method is effective, but it is ineffective in the complex surface area surveys. The precision of velocity method becomes bad, because assigning layers to first arrivals is difficult and crossover points can not be determined easily. In the paper, two near-surface velocity models are simulated, and then inversion velocity models are created by time-term inversion with travel-time difference curve method. At last, through analyzing the inverted results, one fact is found that precision of inversion is improved.