论文部分内容阅读
局部优化和全局优化方法广泛应用到地球物理反演,但是两者各有其优缺点。将两类方法结合起来可以取长补短。将退火遗传算法(SAGA)和单纯形算法相结合,得到了一种高效、健全的2D非线性混合地震走时反演方法。首先,利用SAGA进行大范围的全局搜索,然后由单纯形方法进行快速局部搜索。为了降低层析成像的多解性,我们采用了多尺度逐次逼近的技巧。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。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rlet,Meyer,Marr,缝合带东段上部地壳速度结构研究中。数字模型试验和实际资料的应用表明了方法的有效性和健全性。
Local optimization and global optimization methods are widely used in geophysical inversion, but both have their own advantages and disadvantages. The two types of methods can complement each other. Combining annealing genetic algorithm (SAGA) and simplex algorithm, an efficient and robust 2D nonlinear seismic walk-time inversion method is obtained. First, a large-scale global search is performed using SAGA, and then a quick local search is performed by the simplex method. In order to reduce the multi-resolution of tomography, we adopted the technique of multi-scale successive approximation. The velocity field is divided into different spatial scales. The velocity on the grid nodes is defined as the parameter to be inverted. The parameters are modeled by bicubic spline function model. The positive problem is calculated by finite difference travel time. The inverse problem is solved by multi-scale hybrid inversion method. A numerical simulation of a low-velocity anomaly and anti-walk-away perturbation tests show that the method is effective and robust. We apply this method to the study of the velocity structure of the upper crust in the eastern segment of the Animaqing rlet, Meyer, Marr, northeast of the Tibetan Plateau. The application of digital model test and actual data shows the validity and soundness of the method.