复杂不规则地质体的速度模型反演

Inversion of velocity model for complex irregular geology

针对不规则地质体的速度模型反演问题,提出基于无限插值法生成的贴体网格建立地质模型与走时层析成像相结合的方法。首先采用贴体网格描述不规则地质体,在网格建立的基础上,采用最短路径法得到震源到接收器的走时与射线路径;然后根据走时与射线路径,采用反投影方法(BPT)与阻尼最小二乘法(DLSQR)相结合的技术作为走时反演方法。通过走时反演迭代,最后得到速度模型。整个过程在Matlab中编程实现,并在理论初至上加了10%的高斯噪声,用数值模拟验证。数值验证结果表明:97.5%网格单元理论与反演的速度差在±300 m/s内,对应的相对误差在6.35%之内;理论速度与反演速度基本一致,高低速区域层次分明,反演效果良好,为复杂不规则地质体的速度模型反演提供了新方法。

Aiming at the inversion of velocity model of irregular geological body,this paper proposes a method of combining geological model with travel-time tomography based on body-fitted grid generated by transfinite in-terpolation.First,the body-fitted grid is used to describe the irregular geological body.On the basis of the grid construction,the shortest path method is used to obtain the travel time and ray path from the source to the receiver.Then,according to the travel time and ray path,the back-projection method(BPT)combined with the damped least square method(DLSQR)is used as the travel time inversion method.By the travel time inversion iteration,the velocity model is finally obtained.The whole process is programmed in Matlab,and 10%Gaussian noise is added to the first arrival of the theory.The final numerical simulation verifies the results.The numerical results show that the difference between the theory of 97.5%grid element and the inversion velocity is within±300 m/s,and the corresponding relative error is within 6.35%.The theoretical velocity and inversion velocity are basically the same,and the high and low velocity regions are well-defined and the inversion results are good.This provides a new method for the inversion of velocity in complex irregular geology.