That Was Your Second Warning, Los Angeles. Get Some Extra Water. Now

All right Los Angeles, it's time you take a minute and think a few things over: What are you going to do today so that you are better prepared for when it really happens here.

All these earthquakes you've felt in the past couple days? Sure. The rocking, the rolling, the pool sloshing -- all of it stands as an unnerving reminder how the foundation for our metropolis is a churning vat of tectonic entropy capable of tossing us over at any given moment.

For now, we're okay. The long rolling motion may have freaked you out, but if you live close to L.A. it probably didn't do any damage.

READ MORE: Are LA's High-Rises Ready for the Big One?

True, the Los Angeles Times reported several items fell off the walls at Crate and Barrel's location at The Grove. But the freeway flyovers stand to endure another day's commute. The aqueducts remain uninterrupted. The mid-century dingbats remain optimistically perched above their carports.

At some point, likely sooner than later, that won't be the case. The images from Ridgecrest and Trona show a small sliver of what might -- what will one day -- happen here. Where 25,000 people live in Ridgecrest, there are more than 20 million in Greater Los Angeles, the Inland Empire, and San Diego.

Friday evening's 7.1 shaker rated as a "major" earthquake by U.S. Geological Survey (USGS) standards. It was the second of two sizable earthquakes that struck this week in the Mojave desert, and the largest in Southern California in about 20 years.

Just the day before, a 6.4 magnitude quake hit about 10:30 a.m. on the morning of July 4th. We now know that was a foreshock to the larger quake -- something seismologists like Dr. Lucy Jones had warned us could happen.

Even now seismologists underscore that there remains a small chance that another potentially larger earthquake on the same fault system could yet occur.

READ MORE: 3,000+ Quakes, More Than $100M In Damage: The Aftermath Of 7.1 Magnitude Earthquake Continues

All of the earthquakes have occurred roughly 125 miles north of Downtown Los Angeles. At that distance, the shockwaves attenuate enough so there's virtually no significant damage besides a rattled sense of security.

At the same time, a 7.1 releases roughly four times the energy of a 6.7, the strength of the 1994 Northridge earthquake that killed 57 and dealt roughly $35 billion in damage.

Countless local faults are capable of generating earthquakes as large as (and in some cases larger) than those in the Mojave the past few days. The known faults criss cross Southern California like spaghetti with familiar names like the Newport-Inglewood, the Hollywood, the Raymond, and the Puente Hills fault.

All run under one of the most densely-population metropolitan areas in the nation -- meaning a major earthquake on any of them would be a major disaster. Then there's the local daddy -- the San Andreas fault that's theoretically capable of generating an 8.2. An earthquake of that scale would release about 45 times more energy than Friday's 7.1, and about 180 times more energy than Northridge. At its closest, the San Andreas passes within 40 miles of Downtown Los Angeles, and clips through the cities of Palmdale and San Bernardino.

That earthquake, a major San Andreas earthquake, is the most worrying possibility. Scientists estimate the southern portion of the fault -- the area near Los Angeles -- ruptures roughly once every 150 years. The last time it did so was on a January morning 162 years ago, in 1857, when it produced a 7.9 tremor that shook most what we call Los Angeles. It lasted somewhere between one and three minutes.

The difference between a San Andreas earthquake and a large temblor on any of the other local faults is basically a function of scale. Where a 7.0 on the Hollywood fault would do major damage to Metro Los Angeles and the San Fernando Valley, the same cannot be said for South Orange County or Ventura. An 8.0 on the San Andreas, by contrast, would cause bad damage virtually everywhere between San Luis Obisbo, Tijuana, and the Salton Sea.

READ MORE: Here's What Back-To-Back 7.1 and 6.4 Magnitude Earthquakes Look Like: The Ridgecrest Quakes In Photos

That's what people mean when they talk about "The Big One." The prospect of an earthquake of that scale is the subject of substantial work by the reporters, producers and writers at LAist and KPCC. Our nine-part podcast series The Big One: Your Survival Guide was released earlier this year and examines what will happen when the San Andreas next slips, and what you can do to prepare.

On one hand, that's the things you already know you should be doing, but maybe haven't:

• One gallon of water per person (and pet) per day for as many days as you can store (but definitely at least three).
• Non perishable foods
• Extra meds
• Making sure your apartment building is appropriately retrofitted or your home bolted to its foundation, etc.

It also means planning ahead with your loved ones and your neighbors.

Jones, the Caltech seismologist who has been Southern California's go-to for all things seismic since the Northridge quake, says preparing our social infrastructure is every bit as important as our physical infrastructure.

"I want you to go talk to somebody you care about. Go to your neighbor, go to your church, go to your school, and say what can we do together?" said Jones told us at the end of a Saturday morning interview. "What's really going to determine how we handle a big earthquake in this dense urban area is how well we're working together with our neighbors."

That means having a plan, and actually talking through beforehand with those near to you what you're going to do after the ground stops shaking.

Jones added that any level of shaking serves as a sort-of reminder of what can and will eventually happen here.

"It is the thing that is supposed to be solid -- the earth under our feet -- that is moving on us. It's a distressing experience, long before they become actually dangerous to us," she said.

So make your plan. If you're about to head out the store, a few extra gallons of water never hurts either.

GET READY FOR THE BIG ONE

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The Big One Is Coming To Southern California. This Is Your Survival Guide

How To Get Ready For The Next Big Earthquake. You Asked, We Answered

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