Massively Parallel Computing of Shortest Raypath and Traveltime in 2-Dand 3-D Models
Jason C. Kao, How-Wei Chen · Terrestrial Atmospheric and Oceanic Sciences · 1996
Based on Huygens' principle, the authors present.an accurate and computationally efficient method to compute the shortest ra)rpath and traveltime in a tw'o-and three-dimensional (2-D and 3-D) space of a dis crete block model.The efficiency of the method is achieved through ap proximation, \\1hile the accuracy of the calculated traveltime solely depends on machine precession.The accuracy of the raypath is realized by the small increment in the orientation of the ray incidence.Whet.her the computa tional efficiency and accuracy can be justified depends on the model's com plexity and requirements in its own application.In addition, the feasibility of implementing the algorithm on the Cray T3D Massively Parallel Proces sors (MPP) is proposed.The velocity distribution in a 2-D space is discretized into homogeneous polygonal cells.The search for the shortest traveltime and path between two given points can be reduced to a discrete graph searching.In the gen eral 3D case, the velocity model is characterized by discrete con,rex blocks bounded by polyhedral surfaces.Although the 3-D algorithm is a straight forward extension of the 2-D case, the computing operations in 3-D are much more CPU intensive.The method is demonstrated with examples showing raypaths and wavefronts in 20 and 3D block models.On the basis of these examples, the proposed algorithm is capable of solving the optimal raypaths from di ff er ent source points in parallel on the MPP S)1stem.