Director Brad Peyton brought in Thomas Jordan, USC professor and director of the Southern California Earthquake Center to fact check the script for plausibility. Though both Peyton and lead actor Dwayne Johnson contend that the science portrayed in the film is accurate, Thomas Jordan was quoted as saying "I gave them free advice, some of which they took... but much of which they didn't - magnitude 9's are too big for the San Andreas, and it can't produce a big tsunami."
It is possible for a Nevada quake to trigger an L.A. quake, and for an L.A. quake to trigger a San Francisco quake. The 1992 Landers earthquake, a 7.3 in California's Mojave Desert, triggered a 5.3 quake in Nevada the next day. The 1906 San Francisco earthquake triggered magnitude 5 earthquakes the next day in Santa Monica, Oregon, and Nevada.
After a devastating earthquake in Nepal in April 2015, the film's marketing campaign was adjusted to include information about how to help relief efforts and to give guidance on how to prepare for natural disasters (e.g., a link to the site prepareandhelp.com was added to the newest trailers).
Alexandra Daddario is 14 years younger than Dwayne Johnson, who plays her father, and 15 years younger than Carla Gugino, who plays her mother.
The cast did a lot of their own stunts because director Brad Peyton wanted audiences to see their faces. In the first 15 minutes of the film, Johnson rappels out of a helicopter that's at least 150 feet off the ground to rescue a girl that's in a car suspended off a cliff face set that's 50 feet off the ground. "There was a little bit of a challenge that the script, the story, and the style in which we wanted to shoot it posed to the cast, which I think they delivered on in spades," Peyton tells us. "I wanted to get Dwayne into the back seat and chase him with a 150-foot techno-crane and not cut. I wanted the audience to know that they're seeing Dwayne Johnson do this. This isn't a trick. There's no editing. This is him really doing it." Peyton was thrilled when everyone in the cast stepped up to the challenge. "What's awesome about Dwayne and the entire cast was you presented to them, 'This is the vision for the movie. I want to experience it. I want to see you guys do it.' And they were all in," Peyton says. "I remember in Australia seeing Dwayne practice that, which makes your heart palpitate, because you're like, 'Please do not fall right now. We need to roll cameras, sir.' When you see it, you're like, 'I buy this. This is legitimate.'"