Continuity mistake: During the scene at the airport when the tower OK's the plane to land we can see it is a 707 with TWA-like colors of red and white. Then when there is the shot of the plane on the ground it turns into a DC-8 with orange markings. When the plane takes off into the air the camera shows the 707 again.
Continuity mistake: When the aftershock hits L.A. and destroys Wilshire Plaza, the camera shows the destruction underground and at some point a brick pillar falls over. Instead of being made of brick it's really made out of wood with brick type wallpaper. You can tell this because if the pillar was really made of brick, when it fell over chunks of brick would at least break off. (01:38:20)
Continuity mistake: At the beginning of the earthquake, outside of the office building the entire scene is out of continuity. Just watch the woman with the orange dress.
Continuity mistake: During the fight at the bar, the bald man is lying against the wall, with a man on top of him. Immediately after, barely half a second later, their positions are totally different: the bald man is away from the wall and on top of the other man plus the surrounding people have changed places and pool cues have appeared out of nowhere.
Continuity mistake: When the farmer asks Adams if he knows what he's doing, check the man in the background: He walks inside the ditch, then a shot later he is out and walking inside again; but then another shot afterwards he's out again and walking inside for the third time. All in a matter of 3 seconds. (00:18:40)