三维非均匀地质模型中的逐段迭代射线追踪

地震射线追踪是地震定位、层析成像、偏移等领域的重要正演环节.随着这些领域研究的深入,针对传统的网格结构和层状结构在描述复杂地质模型遇到的很大困难,我们采用大小不等、形状各异的地质块组成的集合体来描述三维复杂地质模型,并用三角形面片来描述地质块之间的物性间断面,理论上可以描述任意复杂的地质模型.为适应任意非均匀速度分布的地质模型,基于费马原理,本文发展了与之相适应的逐段迭代射线追踪方法.该方法属于弯曲法范畴,对路径点采用一阶显式增量修正,相对于传统的迭代法,高效省时.数值试验表明,联合逐段迭代法和伪弯曲法的射线追踪扰动修正方案在三维复杂非均匀块状模型中有适用性和高效性.

Segmentally iterative ray tracing in 3-D heterogeneous geological models

Seismic ray tracing plays a key role in earthquake location, seismic tomography, migration and many other applications. To overcome the difficulty caused by grid-based and layer-based modeling, we describe a 3D complex geologic model as an aggregate of arbitrarily shaped blocks separated by triangulated interfaces. Based on Fermat's principle of stationary travel time, we develop a segmentally iterative ray-tracing (SIRT) method for geological models with generally heterogeneous velocity distribution. The method falls into the bending method category, in which the path points are perturbed by a first-order explicit formula instead of traditional iterative methods. Numerical tests demonstrate that the perturbation scheme of ray tracing is effective in complex 3D heterogeneous block models.