The Big One On The Way? What Happens If A Monster Earthquake Hits California?

Kevin Bostic

With earthquakes and California, it's more of a question of "when" rather than "if" and speculation is running high that the Golden State is overdue for a massive quake. But just what would such an event mean for California?

This week brought increasing talk concerning the San Andreas Fault System, the massive fault that runs 1,250 miles long the edge of the Pacific coastline of northern California. According to some reports, multiple segments of the San Andreas Fault System have enough stored energy to cause major earthquakes on their own.

Most recently, Napa, California saw a magnitude 6.0 earthquake late in August. That quake caused millions of dollars in damage and it still wasn't as powerful as the 6.9-magnitude quake that hit the San Francisco Bay Area in 1989. That quake killed 60 people and caused massive damage throughout the area.

But when people talk about "The Big One," they typically mean a massive quake that hits around 9.0 on the Richter scale. It might seem like a simple leap of three points from the South Napa earthquake of 2014, but remember that the Richter Scale is logarithmic. That means that a magnitude-7.0 quake is 10 times stronger than a magnitude-6.0 quake, and a magnitude-8.0 quake is ten times stronger than a 7.0.

That means that a magnitude-9.0 earthquake would be 1,000 times stronger than the quake that hit Napa earlier this year.

In a state as heavily populated as California, the impact of such a natural event is nigh impossible to imagine -- but that doesn't mean nobody has tried.

When the San Andreas' strike-slip fault does eventually rupture, seismologists estimate that the rupture will take about 55 seconds. That's just about forever in earthquake terms, so "The Big One" is not a misnomer, and the estimated four minutes of seismic waves pushing through the Los Angeles Basin won't be fun to go through either.

LA Weekly ran the numbers on a magnitude-7.8 quake, noting that it would be difficult to determine exactly which buildings and areas would be hardest hit. The United States Geological Survey, though, has a Shaking Intensity Map that shows that harder-hit areas in the LA Weekly's scenario would be the Eastside, downtown, South LA, and Hollywood.

About 40 percent of the deaths in such a quake, and 90 percent of injuries, would come from building collapses, falling air conditioning units, and falling decorative beams. Other deaths and injuries would result, no doubt, from crashing cars, trucks and buses, as well as derailed rail and subway cars.

The disruption to society in the area would be massive as well. Six railroads, nine highways, 12 gas pipelines, nine fiber-optic cables, 19 aqueducts, and 29 power-transmission towers would be affected by the quake. How affected? The USGS predicts that they would be "offset" by an average of 20 feet, resulting in snaps and breakage in just about every case.

That means that transport into and out of an affected area would likely be crippled, as would communication and even reliable flow of clean water.

There is also the potential for other effects. The LA Times noted a study saying that a magnitude-9.0 earthquake along California's North Coast could have disastrous effects even though that area is comparatively sparse in population. The danger: a giant tsunami that would wash away coastal towns, destroy U.S. 101, and cause $70 billion in damage across the Pacific coast.

That scenario predicts at least 100 bridges being lost, with power lines toppled and many coastal towns isolated. Residents would have perhaps 15 minutes notice to flee to higher ground -- and still an estimated 10,000 would die.

In short, the "Big One" would wreak utter havoc wherever it hit, with older buildings crumbling; power, communications, and transport crippled; and the death toll likely rising with each passing minutes.

If there's a bright side, it's the one that LA Weekly points out: California is one of the most earthquake-ready places in the world. Still, only about 40 percent of residents stay stocked up on the recommended three gallons of water for earthquake preparedness.

How likely is a "Big One" to hit California? There's about a 37 percent chance of such a quake happening over the next 30 years, which is pretty high in terms of earthquakes. Virginia in 2011 experienced an earthquake, and that state's chances of such an event were only at about four percent.

[Lead image via HM&A Insurance]