In the wake of the tremendous success of the 1970 disaster-suspense film "Airport", Universal Studios began working with executive producer Jennings Lang to come up with a new idea that would work within the same "disaster-suspense" genre. Inspiration came in the form of the San Fernando earthquake of February 1971. Director Mark Robson and Lang were intrigued by the idea of creating a disaster on film that would not be confined to an airliner, but rather take place over a large area. Producer Bernard Donnenfeld helped produce the film, but was uncredited.