In no particular order:
Earthquake (1974)
This was a fun movie lots of falling buildings and Charlton Heston to boot.
Airport (1970)
The first movie was probably the best, but the sequels had their charm.
The sequels were:
Airport 1975 (1974)
Airport '77 (1977)
This was the sequel where the plane ended up at the bottom of the ocean. Maybe a tribute to the Poseidon Adventure.
The Concorde: Airport '79 (1979)
The Towering Inferno (1974)
Probably one of my most favorite 70's disaster movies. I remember trying to stay up late to watch this movie on t.v.
More Later.