# Difference between revisions of "Dictionary:S-rule/en"

An application of the equivalence principle used in resistivity sounding. Sounding graphs over a series of strata with resistivities ${\displaystyle \rho _{i}}$ and thicknesses hi above a highly resistive substratum possess the same asymptote if the sum of longitudinal conductance (${\displaystyle {\frac {h_{i}}{\rho _{i}}}}$) is constant, i.e., if
${\displaystyle S=\sum {\frac {h_{i}}{\rho _{i}}}={\text{constant}}}$