- Ground-motion model is:
where Sa

_{CU}is in cm∕s2, α_{1}= 5.6897, α_{2}= 1.1178, α_{3}= -0.50 and α_{4}= -0.0060 (σ is not reported). - Only use data from Ciudad Universitaria (CU) station, which is the reference site in the hill zone (rock) of Mexico City. Also derive models for Secretaria de Comunicaciones y Transportes (SCT) and Central de Abastos (CD), which are in lakebed zone, using same approach.
- Weight data so large and small earthquakes equally represented in regression.
- Use Bayesian regression where prior probability distributions of coefficients are assigned based on ω
^{2}model for source, frequency-dependent attenuation parameters and duration from previous studies and random vibration theory. Coefficients are updated using the records. - Compare observed and predicted spectra. Find match acceptable except for event 13 (Ometepec,
25/04/1989, M
_{w}6.9), which was an anomalously intense earthquake. - Derive model for comparison with less direct ways of estimating motions.