Central California is currently in the middle of an earthquake swarm, with up to 18 (and counting) tiny quakes shaking things up over the course of a single day. The situation is not, however, as ominous as it may seem. KTLA reported that the quakes began in the Bay Area late last night and have continued through today. With nothing larger than a magnitude of 3.7, all of the quakes have been relatively small. But should the rising tally give alarm? Probably not. Central California is just in the middle of a run-of-the-mill earthquake swarm. The precise mechanics of what sets an earthquake swarm off aren't clear, but they're pretty common in geologically active areas. The USGS defines them as simply a bunch of small earthquakes clustered around the same locale and time. There's no set limits for either the time or area. In fact, the quakes in a swarm don't even need to stem from the same fault lines. Is a swarm a sign of something bigger on its way, though? Probably not. Although the