# Impedance

From SubSurfWiki

In seismology, impedance of a rock layer is defined as the product of bulk density *ρ*_{B} and P-wave velocity *V*_{P}:

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

The angle-dependent reflectivity is given by the Zoeppritz equation.

## Shear impedance

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

## 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.

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