# Dictionary:Epsilon ε

**1**. Dielectric permittivity; see *Maxwell’s equations*.

**2** The fractional change in the P-wave velocity:

where *c*_{11} and *c*_{33} are transverse isotropy elastic constants^{[1]}.
See *Thomsen anisotropic parameters*.

## References

- ↑ Thomsen, L., 1986, Weak elastic anisotropy: Geophysics, 51, 1954–1966.