Revealing mistake: When the cattle truck falls out of the collapsing highway, none of the cows move a single inch nor fall off, revealing the real truck was replaced with a miniature prop set.
Revealing mistake: When Stewart climbs up the rope to save Sam, in the wide angles he is replaced by an obvious stunt: younger and with different haircut.
Revealing mistake: When the car chase comes to an end, check the curb where the cars drive over: a small ramp has been placed to allow for the stunts.
Revealing mistake: When Adams is inside the trench and dirt begins to pour, he is replaced by an obvious stuntman with a totally different hairstyle.
Revealing mistake: When Denise picks up Corry, he has a silver patch underneath his shirt. Seemingly some sort of protection.
Revealing mistake: When the highway collapses, the miniature prop is missing the delineators and lamp posts.
Revealing mistake: Near the beginning, after a couple of small earthquakes, Fred comes flying out of the dam elevator shaft with a whole heap of water, dead from drowning. But you can see him lift his head out of the water seconds before his friend turns him over and finds him definitely dead.
Answer: There are two versions of the film. A 'film' version which does not include this scene (and others) and a 'TV Miniseries' version. The miniseries version was made to run over two nights and extra scenes were shot to extend the running time.
jle