Impedance

In seismology, impedance of a rock layer is defined as the product of bulk density &rho;B and P-wave velocity VP:

$$Z_\mathrm{P} = \rho_\mathrm{B} V_\mathrm{P}\ $$

The normal incidence (vertical) reflection coefficient between an upper layer i and a lower layer i + 1 is given by

$$R_{i} = \frac{Z_{i+1}-Z_{1}}{Z_{i+1}+Z_{i}} $$

Shear impedance
S-wave impedance is the product of bulk density and S-wave velocity

$$Z_\mathrm{S} = \rho_\mathrm{B} V_\mathrm{S}\ $$

Elastic impedance
Elastic impedance (EI) is an offset (or angle) dependent property for non-normal angles of incidence. It was first described by Connolly, 1999.

P to S converted wave elastic impedance (PSEI)
Also called Shear wave impedance.