APPENDIX: SYMBOLS

The basic material properties and other parameters are

Uniform layer thickness

z

Number of layers

n

Total thickness

Z = nz

Mass density of j'th layer

$\rho_{j}$

Average mass density

$<\!\rho\!\gt$

Mass density perturbation of jth layer

$\Delta \rho_{j}$

Compliance of jth layer

s_j

Average compliance

$<\!s\!\gt$

Compliance perturbation of jth layer

$\Delta s_{j}$

Slowness

$\lambda$, defined equal to $\surd(\rho s)$

Impedance

$\xi$, defined equal to $\surd\rho / s)$

Velocity field

v

Traction field

$\sigma$

The two one-way velocity fields

v⁺ and v^-