# Dictionary:Athy equation

(ath ē’) An empirical equation relating porosity ${\textstyle \phi }$ to depth z that is used in compaction studies based on seismic transit time:
${\displaystyle \phi =\phi _{0}\ \mathrm {e} ^{-bz},}$
where ${\textstyle \phi _{0}}$ is the value at z = 0 and b is an empirical constant.