Thanks to those to have responded.
The project is in a very preliminary state (ballpark figures for total steel tonnage etc.) so information are scarce, but I have found out that the location is in an area called San Luis Potosi.
I have downloaded the USACE Seismic Design Manual No. 5-809-10, as suggested by Mr. Thomas Hunt (I'll send him my phone bill <g>). This manual states that dynamic analysis is required for the worst soil class, regardless of seismic zone. Does the same apply for soil type III, zone A, in Mexico, or is it allowed to use a static lateral force procedure (elastic/plastic?).
There have been mentioned two codes; The Federal District Code for Mexico City (RCFD) and The Government Electricity Commission Code (CFE). Where does "MOC-93" fit into the picture?
Gunnar Hafsteinn Isleifsson