I know the effects weren't as good as now, but
when the earthquake destroys the Wilson building,
you can clearly see that some of the rocks and
columns are wood or foam.
Wait a second, wasn't the TV version released in 1976, or am I mistaking.
No, this is the Universal pictures big screen film.
The TV version was aired in September 1976 as the premiere of NBC's "Big Event", and broadcast in two 90-minute parts. This has extra footage shot (the scenes with Debralee Scott and her anal husband on the plane.) I think Victoria Principal and Marjoe Gortner returned for some extra scenes too. BTW, "Two-Minute Warning" had its plot altered for its TV airings, with Heston returning to shoot new footage. (The first and last film to do this.)