Living in earthquake country is unpredictable

Posted at 9:54 AM, Nov 29, 2019

Living in California, you're probably familiar with the term "earthquake country." Despite extensive studies and research, predicting an earthquake continues to be impossible.

Parkfield, California is about 65 miles east of San Luis Obispo, just over the Monterey County line. It's a tiny town with a population of 18. Driving through it doesn't take long, but when you cross the bridge to get there, the topography is pretty impressive. That's because the San Andreas fault, the largest fault line in California, runs right through Parkfield. It's what separates the Pacific Plate Boundary from the North American Plate Boundary, which is the plate Parkfield sits on.

Despite this town being tiny, the San Andreas fault is its main attraction.

"Believe it or not there are earthquake tourists that come around, there's the type that have their own way of predicting," said John Varia, the owner of the Parkfield Cafe and Inn.

Varian is not just a Parkfield local, but also a native having grown up right near the fault. He remembers feeling two larger earthquakes as a kid, but nothing that was life-changing. Today, the outside of his cafe reads, "Earthquake Capital of the World."

"My dad said when you have lemons make lemonade, and so we embrace the earthquake part of it and be here when it happens.," Varian said.

Tourists aside, Parkfield was the main focus in an earthquake study by the United States Geological Survey. Elizabeth Cochran, a seismologist with the USGS, says on average, there are about 15-20 earthquakes of magnitude 2.0 or larger each year.

"The size of the earthquake is actually related to the size of the fault that splits during the earthquake," Cochran said.

Cochran says the closer you are to the epicenter, of an earthquake, the stronger the shaking would be, but as you increase your distance from the epicenter the shaking becomes less intense but it lasts longer, that's because seismic waves increase over time.

"The San Andreas Fault is a vertical fault," Cochran said. "That means it goes straight down into the crust, and as we go down in the crust, the crust actually heats up and once you get below about 10 miles deep, the crust is too warm to have an earthquake, so we can have an earthquake that's about 10 miles deep but that's about 100 miles long."

The Central Coast side of the San Andreas Fault is the Pacific Plate. John Jabinsek, a geophysics professor at Cal Poly, says the Pacific Plate is moving northwest, while the North American Plate, where Parkfield is, moves southeast.
There's a focus on the San Andreas fault, but there are several smaller faults across the Central Coast, including the San Simeon fault zone, Oceanic fault zone, and the Edna fault zone.

"It's not that these faults are necessarily inactive, but we just don't really know how inactive they are," Jabinsek said.

"One of the faults in this zone hosted the 6.5 magnitude San Simeon earthquake that did quite a lot of damage to Paso Robles and other communities in the area," Cochran said.

That was another earthquake experts could not predict.

Maybe you've heard that having consistent cooler earthquakes means we won't have "the big one," but that's a myth.

"The little earthquakes are just the crust kind of readjusting.

With the recent development of the MyShake app, Californians who are about 15 miles from the epicenter of an earthquake could be given some extra time to duck and cover. A magnitude 4.5 earthquake or higher will send an alert to mobile phones.

"Earthquakes evolve over time and it can take about a minute for a really long earthquake to rupture," Cochran said. "As the earthquake grows, we can see the earthquake grow and the magnitude increase and then we can warn people on the expected shaking that we have."

Some people want to know what that feels like.

"The idea of maybe getting a chance to see one or feel one is intriguing for some people," Cochran said.

It's what attracts so many Parkfield.

"The fault is definitely what made this area so beautiful and makes this area so unique," Varian said.

According to Cochran, the San Andreas fault moves about one inch per year, which gives seismologists a better understanding of how quickly stress in the earth is building up. Still, it's not enough to know when the next quake will hit.