Revealing mistake: In the office tower after the quake there is a panic and workers rush down the stairs only to find them fallen away. After two women fall to their death a man is left hanging on a girder, but falls onto a giant piece of glass. Look at the top of the frame and you will see the airbag shooting our from under it.
Revealing mistake: During the quake, a mother is seen having a plate glass window fall on her face while her daughter screams. Before the mother turns around to show us the gore, look close and you can see a shard of glass already "placed" in her face before the fake glass falls her. Additionally, while not a "mistake", it's clearly a "stuntman" portraying the mother. The face and yelping give it away.
Revealing mistake: When the elevator crashes, there's a really crappy splat of blood on screen that appears abruptly, which is a very obvious over-impression of a painting.
Continuity mistake: When the balcony collapses, the man that was eating chicken disappears in the wide angle.
Revealing mistake: When the California Seismological Institute collapses, the old boss is replaced by a much younger stunt. Also, his sleeves swap between rolled up or not and his tie disappears.
Visible crew/equipment: A white stage light is reflected on the kettle when Stewart visits Denise at her place. (00:14:29)
Continuity mistake: When Stewart and Remy stare at the destroyed building, the sky behind is cloudy and dark, but when the shot focuses on them it is a bright and sunny day.
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.
Continuity mistake: When Denise escapes from the rolling home, she trips and her jeans get covered in dust. A shot later they're clean.
Continuity mistake: Before the mother is covered in glasses, she runs away, her hair covered in dust. A shot later it's clean and shiny. This is because the actress was replaced with a stunt with a wig. (00:58:50)
Continuity mistake: When Corry rides his bike towards the bridge it's too big for him, the seat being lower than the handlebars. A shot later the kid is way taller and the bike is tiny in comparison.
Visible crew/equipment: Stage lights and a boom mic or filming crane are reflected on Miles' helmet when he is about to ride on the track.
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 the parking lot building collapses, check the right side where the cars are. All along the ground level there's a rectangular strip where the film of the miniature building was pasted on top of the film with the real-sized parked cars. Note how all the debris falls behind that strip, it never falls on top of the cars, as if there was a weird black hole of some sort. (01:37:54)
Continuity mistake: When Stewart is about to save Sam, in the wide angle Sam is lying down, both legs opened wide. In the close-up he is crouching next to the railing. This swaps back and forth.
Revealing mistake: When the group is trying to escape the office building, a woman in pink falls into the void. Watch when she falls and you'll notice that the stuntman's wig flies off (it's to the left of his head).
Revealing mistake: During the earthquake, when the window-shop bursts, the airbag that breaks the windows is very, very noticeable. (00:53:13)
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.
Continuity mistake: During the quake at the Seismological Institute, one of the men's shirts changes from beige to dark brown between shots.
Continuity mistake: When Stewart arrives at Denise's place, a book suddenly appears on top of the books on the second shelf.
Chosen answer: Before he put the uniform on, he was a complete nobody, having the respect of no-one. Now that he's in uniform, he demands that people should respect him, and coupled with the powers of Martial Law (where looters can be shot on sight), takes the lack of respect too far and shoots them.
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