CNN  — 

Right after a 6.4 magnitude earthquake rocked Southern California on July 4, filmmaker Ava DuVernay, a lifelong Angeleno, tweeted that it was the longest quake she’d ever felt.

“It was so long,” she wrote, “I thought for the first time ever is this the Big One?” But it wasn’t even the biggest tremor Californians would see that week, with a more powerful 7.1 quake coming just a day later.

Ultimately, neither was the fabled Big One, a catastrophic earthquake that could occur along the San Andreas Fault and that geologists have warned is likely “overdue.”

This week was just a reminder. Jason Corona, whose family owns a restaurant in Ridgecrest, near the epicenters of the earthquakes, described feeling uneasy as the aftershocks kept him awake late Friday night.

“It’s constant adrenaline,” he said, “because we don’t know if the little one is going to be the next big one.”

He and other residents last week woke to headlines driving the point home: “4th of July earthquake won’t delay the Big One,” read one on Friday from the Los Angeles Times; The New York Times reported Thursday’s earthquake was “a reminder that the Big One lurks.”

Earlier this year, KPCC, a public radio station in Southern California, released a new podcast titled “The Big One: Your Survival Guide,” aimed at coaching Californians to prepare for a potentially devastating earthquake.

An employee works at the cash register at Eastridge Market, near broken bottles scattered on the floor, following a 7.1 magnitude earthquake, on July 6 in Ridgecrest, California.

As the last large earthquake fades in the rearview mirror, people inevitably forget about the looming menace, said Albert Adi, a small business owner who’s lived in Southern California since 1980. “And then you have a big one come and it reminds you.”

“Everyone is wondering, ‘Is this getting close to the Big One?’” he added. “God knows it’s not an easy feeling.”

The Big One is coming

According to geologists, a major earthquake along the San Andreas Fault is likely “overdue.”

The southern San Andreas Fault has typically seen large earthquakes every 150 years, according to the US Geological Survey. And since the last large earthquake there occurred in 1857, the southern segment of the fault “is considered a likely location for an earthquake” in the coming years.

A major 7.9-magnitude quake in San Francisco in 1906 means there’s a slightly lower chance of a major earthquake happening in the northern part of the state, the USGS website said.

Many residents, like Steve Rios of Riverside, California, are acutely aware of the threat.

“I would honestly say it’s something Californians are always cognizant of because of the San Andreas Fault being here,” he said.

“We’re standing on two different (sides) of the fault line,” he pointed out. “It’s kind of a scary feeling.”

This week’s tremors probably won’t increase the likelihood of a major earthquake on the San Andreas Fault, seismologists said. They occurred near Ridgecrest, north of the fault.

But they also don’t make it less likely, Dr. Lucy Jones, a seismologist with the California Institute of Technology, told reporters Thursday.

There’s about a 2% chance of the Big One occurring each year, Jones said on Twitter this week, or about 1 in 20,000 every day. While the chances may not be high, residents shouldn’t be caught unaware.

“One should always be preparing for a Big One,” she said.

According to the USGS, such an event would likely be preceded by a period of increased seismic activity for several years. Over the last two decades, Jones said Thursday, Southern California has experienced “an extremely quiet time” when it comes to seismic activity.

But going forward, “this is more what we should be thinking about,” she said.

‘I don’t think anyone’s prepared’

Rachel Higgins, a graduate student in Diamond Bar, California, said that like all Californians she’s heard of the so-called Big One. It’s “part of California legend in a way,” she said, but admitted she hasn’t prepared for it at all. That will probably change going forward.

“It’s going to be a lot more urgent in my mind,” she said.

Rios said that as a kid he and his peers were taught to “duck and cover” and be prepared.

That said, he doesn’t think many Californians are ready. He keeps a supply of water and food on hand, maybe some extra gas in reserve, he said, “but I don’t think anyone’s prepared for something that catastrophic.”

A resident inspects a crack in the earth after a 6.4 magnitude earthquake struck on July 4 near Ridgecrest, California.

Beth McCoy, who lives in Glendora, California, isn’t too anxious.

“I’m not hugely worried,” she told CNN. “I am a structural engineer, so I’m aware of the risks.”

“My husband found it amusing when we bought our houses that I was crawling under the house, checking out the foundation,” she said.

She thinks they’re “fairly prepared.” They bolted their bookcase to the wall as soon as they moved in to prevent it from falling over. As for food, she believes their garden could last them indefinitely.

Corona said this week’s earthquakes have caused him to reconsider whether he’s actually ready.

“I know I have personally switched onto the ‘be prepared’ wagon,” he told CNN. “I think everybody’s been pretty lackadaisical about it, but now I feel people are going to get on board with it a lot more. I know my family has.”

‘You have to keep on living’

Adi, who also studied engineering, said over the years he’s seen a lot of improvement when it comes to construction regulations aimed at curbing the extent of the possible devastation.

In October 2015 Los Angeles passed sweeping seismic regulations, requiring thousands of buildings be retrofitted to withstand violent shaking. San Francisco enacted a similar law in 2013.

Meanwhile, the state has been working on a statewide early alert system, called the California Integrated Seismic Network. The system would not only warn the public, but would also interface with critical infrastructure to automatically shut off some parts of the state’s infrastructure, like train systems.

Gov. Gavin Newsom said Saturday the system is about 70% completed, but still requires some further expansion.

But the governor also stressed each individual’s responsibility to prepare.

Adi, a father of four, has taken a more hands-on approach.

He’s warned his kids of the danger and made them aware of best practices, he said. They know to not panic, to keep their eyes open for downed power lines and to get in touch with their parents. And he keeps enough bottled water and dry food stockpiled in his garage to last several weeks, he said.

Everyone he knows takes the threat seriously, he said, but residents can’t live in a perpetual state of fear. “We know how dangerous it is … but you have to keep on living.”

Ultimately, he said, it’s just one of the tradeoffs of living in a place with beautiful weather and good job opportunities.

“It’s the risk you have to accept by living here in Southern California,” he said.

“Hopefully,” he added, “everything will work out.”

CNN’s Sarah Jorgensen, Alexandra Fields and Chris Audick contributed to this report.