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为了解决复杂速度模型中的走时正、反演问题,例如:含不规则起伏地表、不规则地下波阻抗界面、以及不规则速度异常体的复杂地学模型,本文采用三角网格单元模型参数化下的分区多步改进型最短路径算法,实现了多震相地震射线的追踪计算,结合共轭梯度法求解带约束的阻尼最小二乘反演问题,实现了多震相走时联合同时反演成像的方法技术.当界面起伏较大时出现散射,从而造成散射点所在区域射线密度过密,导致该区域内速度和界面的过度更新.为了克服上述问题,我们在同时反演中引入了射线密度的概念,从而有效地解决了上述过度更新问题.数值模拟实验表明:采用三角网格单元进行模型参数化,可保证在复杂模型中的正演计算具有较高的计算精度;同时反演中可以准确地刻画不规则异常体和不规则反射界面.因此,本文提出的走时成像方法技术具有较广的实用价值.
In order to solve the problem of forward and inverse traveltimes in complex velocity models, such as complex geologic models with irregular surface and irregular wave impedance interface and irregular velocity anomalies, this paper uses the triangular mesh element model to parameterize The multi-step improved shortest path algorithm is adopted to realize the tracking calculation of multi-seismic phase seismic ray. Combined with the conjugate gradient method to solve the constrained damped least square inversion problem, Method and technique, scattering occurs when the interface fluctuates greatly, which results in the ray density in the region where the scattering point is located is too close, resulting in over-renewal of the velocity and interface in the region.In order to overcome the above problems, we introduced the radiation density Concept, so as to effectively solve the above-mentioned over-renewal problems.Numerical simulation experiments show that using triangular grid elements for parameterization of the model can ensure high computational accuracy of forward modeling in complex models and can be accurate To describe irregular anomalous body and irregular reflection interface.Therefore, the walking time imaging method proposed in this paper has a wide range of With value.