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将遗传算法和单纯形算法相结合,得到了一种高效、健全的2D混合地震走时反演方法.把速度场划分为不同的空间尺度,定义网格节点上的速度作为待反演参数,采用双三次样条函数模型参数化,正问题采用有限差分走时计算方法,反问题采用多尺度混合反演方法.首先在较大的空间尺度内反演,然后减小空间尺度,将大尺度的反演结果作为次一级尺度反问题的初始模型,再进行混合反演,如此类推逐次逼近全局最优解.一个低速度异常体的数值模拟试验和抗走时扰动试验表明该方法是有效和健全的.我们将该方法应用到青藏高原东北缘阿尼玛卿缝合带东段上部地壳速度结构研究中,并与前人的成果进行了对比.
Combining genetic algorithm and simplex algorithm, an efficient and robust 2D seismic traveltime inversion method is proposed, which divides the velocity field into different spatial scales and defines the velocity of the nodes on the grid as parameters to be inverted. The bi-cubic spline function model is parameterized, the finite-difference traveltime calculation method is adopted for the positive problem, and the multi-scale hybrid inversion method is used for the inverse problem. Firstly, inversion is performed on a larger spatial scale, then the spatial scale is reduced, The results are used as the initial model for the inverse problem of the next-level scale, and then the hybrid inversion is performed, and so on. The results of numerical simulation and anti-walk-away perturbation tests show that this method is effective and robust We apply this method to the study of the upper crustal velocity structure in the eastern segment of the Animaqing suture zone in the northeastern margin of the Qinghai-Tibet Plateau and compare it with the previous achievements.