Empirical relationships between seismic velocity V in ft/s, geologic age T, true formation resistivity ρ in ohm feet, and depth of burial z in feet:
z is sometimes taken to be the maximum depth to which the formation has ever been buried, not necessarily its present depth. See Faust (1951, 1953). The reciprocal of the second equation above is sometimes written with three constants (k,a,b) to be evaluated empirically from sonic-log transit time (Δt) data:
Named for Lawrence Y. Faust, American geophysicist.