The BIG ONE is coming, but you may get a warning right before it hits. Here's how

Early warning system is being built now, will come online in 2018.

After years of planning and testing, California is about to get an early warning system for earthquakes. The system will be rolled out in phases, and should provide valuable warning to people, thus saving lives.

LOS ANGELES, CA (California Network) - California is earthquake country, and it is prone to devastating catastrophes. Sometime within the next thirty years, scientists predict "the Big One" will hit, and could destroy critical infrastructure across Southern California. This is why state officials are rushing the system into service.

The Big One has been predicted for decades, but only recently have scientists uncovered the evidence that proves how close it is. The quake will strike the San Andreas Fault, which marks the boundary between the Pacific Plate and the North American Plate. This fault is capable of generating a massive earthquake. Scientists have proved it happens on a fairly regular basis, and earlier this year scientists published the evidence that tells us how much time we have left. It's not much. The quakes strike in 200-year intervals or less.

The last great quake in Southern California was the 1857 Tejon quake. More recent quakes in California have made headlines, but none have approached the power of the Tejon quake or the Big One that is coming.

The Big One will be 7.2 to 7.9; it will last about two minutes, which is a lot longer than the 10-30 second quakes Californians are accustomed. The shaking will be more intense, and damage will be much more significant. The quake is expected to strike between Los Angeles and Bakersfield within the next 30 years.

An early warning system, like those used in Japan, is a lifesaver. Californians know what to do in an earthquake. Instinctively, they dive under desks or cram under doorways. Many more run outside where they assume they are safe, but this is a dangerous practice as roofing, masonry, and glass can fall. Most try to enjoy the ride and become excited. But few people will enjoy the Big One.

The aftershocks will begin almost as soon as the Big One ends, and they will be debilitating, hampering rescue efforts. Key infrastructure, from roads to power to water, will be cut off. It will take days for help to arrive in some places.

The early warning system works by detecting the first seismic waves, deep below ground. A warning is sounded across the alert area. For people at the epicenter, there is no time between the warning and the shaking. That's because the system does not predict quakes, it can only warn once they've begun.

People living farther away will have better luck.  They will get a few seconds to take cover. In addition to sounding an alarm, the system will automatically open firehouse garage doors and stop commuter trains. Kids in school will duck and cover before shaking starts. Thousands of lives could be saved.

The system has been in development for many years, and the state has been criticized for its $10 million price tag, and for its slow rollout. But officials say they just want to make sure it works before deploying it. The system will not be heeded if it issues false alarms.

Eventually, the system will span the entire west coast from Mexico to Canada.

The system will go online in 2018 and will spread in phases. Eventually, the general public will be able to receive alerts on their phone. The network is now under construction.