Factual errors: The San Andreas fault is incapable of suffering an earthquake measuring 10.5 on the Richter scale (100 times as strong as the largest earthquake ever recorded). The Richter scale measures strength as a function of fault length, and the fault in question is far too short to generate such a massive jolt (which would be felt all over the world).
Errors in geography: The Space Needle falls towards the side with the steps leading up to the base, which is the north side. It falls along a street in between brick buildings. The Space Needle actually has a football stadium, roller coaster, and an opera house to the direct north of it.
Errors made by characters (possibly deliberate errors by the filmmakers): In the news broadcast regarding martial law, martial is spelled "Marshal".
Factual errors: A 10.5 earthquake as represented in the movie, would actually be much larger than depicted. People would not be able to walk around so freely as they are doing (at a 10.5, the levels of sight and sound would be distorted). Damage would also be total, damaging much more than shown (the destruction would also reach areas as far away as Michigan or possibly even New York).
Factual errors: A 10.5 earthquake would cause massive tsunamis, something that is not depicted in the movie.
Factual errors: The San Andreas Fault meets land around the Colorado River Delta in Mexico, not Long Beach, California.
Errors in geography: Barstow, California is about 110 miles inland from the Pacific. It is not in the San Fernando Valley as depicted.
Factual errors: The San Andreas Fault would not split apart, since it is a transform plate boundary, when two plates grind past each other. Only a divergent boundary would split apart as shown, and those only occur in the ocean apart from an area on land where two plates are pulling apart, this being the Great Rift Valley in Africa.
Errors in geography: When Dr. Samantha Hill and FEMA Director Roy Nolan are placing the warheads at the six sites for detonation, the computer screen identifying the geographical location of the Washington State warhead actually has the Washington State warhead being placed and detonated in Oregon.