井间地震层析成像初始速度模型

地震直达波走时层析成像可归结为求解一个大型的、稀疏的、常常是病态的线性方程组.求解方程组常用的迭代法,需要一个比较合理的初始猜测解,也即是初始速度模型.初始模型关系到反演的效率甚至成像的正确性.本文在前人研究基础上提出一种生成模型网格节点初始速度方法,假定震源到检波点路径为直线,记录每条射线穿过的单元和统计每个网格单元穿过的射线数目、自动拾取网格节点所在单元的数目等.实例中,由原始数学模型的正演旅行时资料生成节点初始速度模型,效果可以.最后,分别采用均匀模型和本文方法生成的初始模型进行迭代反演,通过比较,证实该自动生成节点初始模型的可行性和可靠性,并对存在的问题进行讨论和解释.

Initial velocity model of crosswell seismic tomography

The direct wave tomography is to solve one large-scale,sparse,ill condition linear equation.The rational initial solution and speed model is commonly used in the iterative method of linear equation.The initial model concerns the exactness and efficiency in the inversion.The paper puts forward a method to produce the node initial speed of the models based on the former study.The straight line from source to receive is assumed especially,the program records the cells for each ray,and makes the statistics of the ray number cross each cell,automatically picks up the nodal number of cells and so on.In the instance it is fine that the initial node speed produced by the forward travel time based on the primitive mathematics model.Finally we made the iterative inversion between the homogenous model and the initial model produced by our method separately.We verify that the produced automatically model is the feasibility and dependability through comparing,and discuss and explain about the existing problem.