APPLICATION OF THE PERFECTLY MATCHED LAYER (PML) ABSORBING BOUNDARY-CONDITION TO ELASTIC-WAVE PROPAGATION

A method is presented for application of the perfectly matched layer ( PML) absorbing boundary condition (ABC) to the P-SV velocity-stress fi nite-difference method. The PML consists of a nonphysical material, co ntaining both passive loss and dependent sources, that provides ''acti ve'' absorption of fields. It has been used in electromagnetic applica tions where it has provided excellent results for a wide range of angl es and frequencies. In this work, numerical simulations are used to co mpare the PML and an ''optimal'' second-order elastic ABC [Peng and To ksoz, J. Acoust. Sec. Am. 95, 733-745 (1994)]. Reflection factors are used to compare angular performance for continuous wave illumination; snapshots of potentials are used to compare performance for broadband illumination. These comparisons clearly demonstrate the superiority of the PML formulation. Within the PML there is a 60% increase in the nu mber of unknowns per grid cell relative to the velocity-stress formula tion. However, the high quality of the PML ABC allows the use of a sma ller grid, which can result in a lower overall computational cost. (C) 1996 Acoustical Society of America.