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Was the Napa Quake the Dreaded “Big One”? Is it Coming Soon?

Damage from the Napa Quake

Damage from the Napa Quake

(CNN)-

Relax. This quake wasn’t a sign that the dreaded “Big One” is coming — at least not yet.

The 6.0-magnitude tremor that jolted Northern California on Sunday sparked concerns about whether a more catastrophic earthquake is looming.

After all, the infamous San Andreas Fault is due for its epic every-150-years rumble. And when the next “Big One” hits, one seismologist said, it would be “a major disaster for the nation.”

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But the quake Sunday, centered about 6 miles southwest of Napa, wasn’t on that fault line.

“I don’t think we can make any connection on that,” CNN meteorologist Chad Myers said. “This is on a different fault — still part of the same system, still the plates are still shifting from California, the North American Plate and the Pacific Plate.”

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When will the ‘Big One’ strike?

Catastrophic earthquakes seem to strike along the southern San Andreas Fault about once every 150 years, the U.S. Geological Survey said, citing studies examining the past 1,400 years. The last time an enormous temblor on the fault struck Southern California was in 1857.

“There’s a real likelihood of a major, major earthquake in the next 10, 15, 20 years,” California Lt. Gov. Gavin Newsom said.

Newsom is former mayor of San Francisco, a city that sits near the Hayward Fault and the San Andreas Fault, “the one that fear is most instilled in us.”

But the San Francisco Bay Area is less likely to see a massive earthquake soon, as only about a century has passed since the great 1906 earthquake.

Yet “moderate-sized, potentially damaging earthquakes could occur in this area at any time,” the Geological Survey warmed.

In 1989, a 6.9-magnitude quake struck the Bay Area during baseball’s World Series. The Loma Prieta earthquake caused 63 deaths, 3,757 injuries and an estimated $6 billion in property damage, according to the Geological Survey.

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What about the 1994 Northridge quake?

That mammoth tremor wasn’t on the San Andreas Fault; it actually occurred on a fault that no one knew about.

That 6.7-magnitude Los-Angeles area quake killed 57 people and caused $42 billion in total damage.

But even the Northridge quake could pale in comparison to the devastation that the “Big One” on the San Andreas could bring.

“It would be like having a Northridge here and Northridge here and Northridge here,” Caltech seismologist Kate Hutton said this year, indicating swaths of a California map. “It covers such a wide area that it would be … a major disaster for the nation.”

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Why is the San Andreas Fault so notorious?

The San Andreas is considered “the ‘master’ fault of an intricate fault network,” the Geological Survey said. It’s the fault responsible for the 1906 San Francisco earthquake, which killed about 700 people.

The 800-mile-long fault is the boundary between the Pacific Plate and North American Plate. And because the Pacific Plate shifts about 2 inches a year, the Geological Survey said, Los Angeles and San Francisco will become next-door neighbors (though not for about 15 million years).

So while it’s impossible for the San Andreas to sweep California out into the ocean, the Geological Survey said, southwestern California is slowly — very slowly — sliding past the rest of the state toward Alaska.

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