近地表介质地震初至波层析成像

发展了适于复杂近地表介质的初至波层析成像方法.介质单元的速度用双线性函数表示,推导了计算Jacobi矩阵元素的解析公式,提高了精度和速度;初至波正演计算采用最新研究的动态网络最短路径射线追踪方法,克服了同类方法得到的射线路径呈之字形、计算出的旅行时比实际旅行时系统偏大的缺陷;用LSQR算法求解该大型约束最优化反演问题.用该方法求取塔里木盆地边缘复杂山地的近地表速度和静校正量,取得了良好的应用效果.

First Break Tomography for Near-surface Layers in Seismic Exploration

A tomography method of seismic first arrival traveltime for complex near-surface layers is developed. The velocity in a rectangular cell is represented as a bilinear function with depth and lateral position, and the analytic formulas for computing Jacobin matrix elements are deduced to improve the computation precision. The new shortest path ray-tracing method with dynamic network is used to calculate synchronously all type of first break traveltime and raypaths more accurately than others with fixed network. The inverse equation is resolved by using constrained least square QR decomposition algorithm. The method has been applied successfully to obtain effective near-surface velocity structure and static values, from field data, in mountainous district of Tarim Basin, China.