pml-吸收边界.pdf

: .
B of detail a 3D finite-difference scheme for PMLs and provide
numerical examples.
Introduction
The Perfect Matching Layer (PML) absorbing condi- for wave absorption at the boundaries of numerical models.
tions were first developed for numerical simulations of elec- Although they are attractive for their simplicity of imple-
tromagnetic wave propagation to avoid reflections at the mentation, the minimal number of grid nodes required, and
boundaries of the discrete model (Berenger, 1996). Subse- their satisfactory absorption of body waves under a wide
quently, the method was successfully extended to the field range of incidence angles, they handle surface waves, which
of elasticity, where a very similar system of equations gov- are essential and frequently encountered in geophysical ap-
erns the dynamics (Chew and Liu, 1996; Collino and plications, poorly.
Tsogka, 2001), poroelasticity (Zeng et al., 2001) and aniso- On the other hand, PMLs are slightly more complex to
tropic media (Becache et al., 2001). The evolution of this implement and they require a finite number of nodes (usually
tool, first born in the electromagnetic field and then adopted 5 to 10), but they provide an excellent absorption of body
by developers of elastodynamics modeling, is reminiscent of waves, do not loose efficiency at shallow angles, and mostly,
what happened before for staggered-grid, finite-difference they are very effective even with surface waves. The spuri-
schemes (Yee, 1966; Madariaga, 1976; Virieux, 1986). ous reflections at model boundaries can be made arbitrarily
As shown by Chew and Liu (1996), the implementation small by increasing the thickness of the PML layer at the cost
of PML is equivalent to the introduction of a system with of additional computation. However, an absorption level sat-
stretched c