基于水平集方法的复杂地质速度模型表达

Representation of complex geological velocity model based on level set method

地质速度模型表达的难点在于对复杂地质现象的精确描述和对正、反演应用的有效支持。提出了一种将速度间断面信息以隐函数的零等值面形式内嵌于速度模型的表达方法,多重拷贝策略使得相邻的速度块体互不干涉,妥善处理了在速度间断面处插值速度信息的矛盾。该表达方法适于描述复杂地质构造下的速度模型,如多值层面和具有非流形性质的断裂层面。在基于射线理论的应用中,利用符号距离场和速度间断面二叉树能迅速获得空间任意点的速度信息,检测射线与速度间断面的相交关系,并使射线在速度间断面处严格执行Snell定律,提高了射线路径的正确性。两组射线追踪的应用实例验证该表达方法的有效性。

The difficulties in the expression of geological velocity model are the accurate description of complex geological phenomena and the effective support for the forward and inverse applications. We presented a novel representation method for describing velocity models. Velocity discontinuity was embedded into model in the form of zero-value contour of an implicit function. Multi-copy strategy was to properly handle the contradictory interpolation of velocity value at the boundary of discontinuities. The representation method can be applied to describe very complicated velocity models such as the faulted interface with non-manifold nature and multiple value surfaces. In applications based on the ray theory,signed distance field and velocity discontinuity binary tree enable fast access to velocity information of arbitrary point and easy detection of ray-interface intersection. The model can make the ray propagate positively and honor Snell＇s law strictly when facing velocity interface and thus improve the accuracy of ray path. Two groups of ray tracing examples verify the effectiveness of the method.