It is what it is, but that's good enough - and quite a bit better than its '70s disaster-era progenitors.
One certainly cannot deny that San Andreas delivers on the promise inherent in its title: it really is a feature-length road trip up the San Andreas fault, which just happens to be periodically shaking California to pieces along the way. That may not sound like much of a plot, but the film vastly improves upon the approach of its obvious disaster-era progenitor, Earthquake (1974), which never adequately answered the question: after two minutes of tremors, what can we do for the rest of the movie except dig people out of the rubble? Propelled by a continuing series of quakes spread out over the entire state, San Andreas is all forward momentum and non-stop action, but with enough narrative focus to avoid letting the calamity totally engulf the picture.
Dwayne Johnson plays Ray, a rescue-copter pilot going through a divorce from his wife Emma (Carla Gugino), whose new boyfriend Daniel (Ioan Gruffudd) does not look like an ex-wrestler, meaning he cannot possibly be man enough to replace Ray. Fortunately for Ray, two science guys, Lawrence (Paul Giamatti) and Kim Park (Will Yun Lee) have figured out that a humongous quake is about to destroy California, which will give Ray a chance to prove that Emma should stay with him. This is actually achieved rather quickly, when he whisks her off a collapsing rooftop in downtown Los Angeles; the plot complication, such as it is, arises from the fact that Ray and Emma's daughter Blake (Alexandra Daddario, introduced to us in a flattering poolside bikini shot, because obviously we can't care what happens to her unless she's hot) is in San Francisco with Daniel. So away go Ray and Emma on their rescue mission, first in Ray's copter, then a stolen vehicle, then a stolen boat.
The notion that Ray, a professional rescue worker, is abandoning his post in an emergency is never acknowledged let alone questioned, because movies are all about family these days - at least, that's an easy way to generate a little rooting interest. It also goes without saying that using the company copter for your personal needs and stealing someone else's car is okay as long as you're the protagonist, because - hey, it's only a movie!
Strangely, despite these questionable narrative leaps, San Andreas never completely matriculates into the "Dumb Movie" school of filmmaking; the scenario manages to maintain at least a small illusion of credibility, asking us to engage with the characters as if they are people in genuine peril, not merely pawns in an empty spectacle. It's a sign of what's right in the film that when one of the scientists dies on a collapsing bridge, the sequence is played as a tragedy, not an aint-it-cool moment of awesome special effects.
Likewise, San Andreas mimics the reserved (a relative term, I know) approach to vast destruction seen in Godzilla (2014): much of the action is shown from the point of view of the distraught characters instead of lovingly photographed like epic disaster porn. Although San Andreas is filled with collapsing buildings, tidal waves, fires, and explosions, not all of these scenes are show-stopping set-pieces; often they are glimpsed on the fly as Ray and Emma race by - relegated to sideshow status while the film maintains focus on the their quest to save Blake. It's almost as if the filmmakers thought they were making a real movie in which we cared more about the characters than the quake.
In fact, San Andreas lingers on the verge of being something a little bit better than a by-the-numbers blockbuster. In old school disaster movies, characters tended to be clearly divided into heroes, victims, and villains. Ray is clearly the archetypal disaster movie hero; however, it's a nice touch that Blake, though serving the function of victim in need of rescue, does not sit around waiting for her brave daddy to arrive; she takes action, seeking higher ground, instead of blindly following the panicked crowds. Sadly, this element gets a bit jumbled; with all the chaos of plans gone awry, it's not entirely clear whether Blake's actions will improve or diminish Ray's chances of getting to her in time.
This is not the film's only squandered opportunity to better itself. San Andreas initially avoids offering a typical disaster-movie villain. These take one of two forms: either they are responsible for the disaster, or they irresponsible in the way they save themselves at the expense of everyone else. The obvious candidate here is Daniel, who is - somewhat surprisingly - presented as a halfway decent guy. Yes, he abandons Blake in a crisis, but not out of self-interest; he really seems to be in a complete state of shock. Unfortunately, as the shock wears off, so does the film's sympathy for him, morphing the character into a traditional prick who pushes others out of the way to save himself, until his own efforts ironically put him in the wrong place at the wrong time.
Which I guess means that the film is happy to revert to clichés. Ray, Emma, Blake, and a couple of British immigrant Blake found along the way are okay, which means it's a happy ending all around on the big screen, in spite of presumably millions of corpses buried beneath debris from one end of the coast to the next. Presumably, Ray and Emma will live happily ever after, now that she sees how useful Ray is during a crisis - though how that's going to sustain a relationship during those long periods of time when California isn't quaking itself into a pile of rubble, remains unclear. Hopefully, Giamatti's science guy can spot another earthquake on the near horizon.