We describe the application of a bayesian linear regression technique
to the problem of deriving strong-motion attenuation relations. This a
pproach provides a conceptual framework for the formal incorporation o
f knowledge about the involved phenomena that comes from sources other
than the observed data (prior information, according to the bayesian
terminology). The procedure produces numerical solutions that are more
stable and rational than those obtained from conventional regression
schemes. We illustrate the use of the proposed technique with the deri
vation of attenuation laws for the Fourier acceleration spectrum, as a
function of magnitude and distance, at a hill-zone station in Mexico
City.