It’s ‘Earthquake Season’: Join California’s Great ShakeOut

Drop-Cover-Hold On

Participants in the Loma Prieta 25 symposium, held in Oakland last year, stopped their plenary session at 10:15 a.m. to drop, cover and hold on. (Andrew Alden/KQED)

One week from today, on Oct. 15, more than 10 million Californians will stop what they’re doing and take part in an earthquake exercise. The event is called The Great California ShakeOut, and it will help save a bunch of people a lot of trouble some day.

Even in California, people have trouble thinking about earthquakes. We can slide into a kind of mental paralysis — we know it’s good to prepare, but when we think about the massive devastation of a major quake, it seems like too much to handle.

Here’s the Drill

The answer is: don’t think. When the ground starts to shake — not just a jiggle, but a real earthquake — the experts want you to take three actions without thinking about it:

Drop. Cover. Hold on.

“Drop” means get down, not up. A big earthquake will knock you down, so get down first. Stay down.

“Cover” means cover your head and neck, or get yourself underneath a table or a desk — whatever will protect you from falling things. A big quake won’t let you stand up and stagger somewhere else.

“Hold on” means grab that table or desk and don’t let go until the shaking stops.

That’s what ShakeOut participants will do on 10/15, at 10:15 in the morning. When you practice, hold on for a whole minute. That may seem like forever, but a major earthquake shakes hard for at least that long.

These three actions give you the best chance of coming through a quake uninjured. Experience has shown that, in California, it’s not collapsing buildings that cause most injuries; it’s large household objects, flying and toppling. Stay injury-free, and everything that follows is easier.

Is That All?

“Drop, cover and hold on” should be as automatic as putting on a seatbelt. It’s simple enough for schoolkids, who are big participants in the ShakeOut drill. If you have children in school, do the drill yourself wherever you are. That can start important family conversations later.

Bay Area earthquake probabilities
Major earthquake faults in the Bay Area with their odds of producing a magnitude 6.7 quake in the next 30 years. (U.S. Geological Survey)

Aren’t there more details? Of course. The Earthquake Country Alliance has a page with instructions for special cases: if you’re driving, if you’re in a wheelchair, and so on.

That page is Step Five of the Seven Steps to Earthquake Safety, but it may be the best starting point for exploring earthquake preparedness. If you worry about dealing with the aftermath, you can go forward to Step Six. If your thoughts turn instead to preparing in advance, you can visit the earlier steps.

The “drop-cover-hold on” drill is appropriate for any location you spend time in: your workplace, the places you go for entertainment, even your church. Keep it simple. Spread the word.

What Are the Odds?

The Bay Area has about a dozen seismic faults that are capable of giving the whole region a damaging shake. When scientists add up the odds from each fault, they estimate the Bay Area has a two-in-three chance of suffering a major, magnitude 6.7 quake during the next 30 years.

News outlets fixate on the biggest possible earthquakes. That’s natural for them. But the U.S. Geological Survey’s latest estimate for the whole Bay Area is that we can expect about eight magnitude 5 quakes each decade, and about one magnitude 6 quake every 30 years.

Magnitude 5 and 6 earthquakes are called moderate events. The threat they pose is like the threat from a fender-bender in your car: it won’t kill you but you still want to avoid it. Think of the magnitude 6.0 Napa earthquake of August 24, 2014 as typical.

What Else Should I Know?

Dealing with earthquakes doesn’t require much science knowledge, but it’s worth knowing a few facts.

  1. Large earthquakes come in a distinct sequence: the brief thump of P waves, the short rattle of S waves, then the long, violent shaking of surface waves.
  2. Aftershocks follow every significant earthquake. If they happen at shallow depths, they can do more damage locally than the main shock.
  3. There’s no earthquake weather, no relationship to the Moon and planets, no earthquake season.

Even if quakes have no season, October is earthquake month for Bay Area old-timers. It goes back to 1989, the year of the Loma Prieta earthquake, when, on October 17, at 5:04 p.m., everyone got a taste of what happens in a large seismic event. Ask any old-timer about it.

It’s ‘Earthquake Season’: Join California’s Great ShakeOut 8 October,2015Andrew Alden

  • David Shapiro

    RE: Your “fact” #3: Nowhere at the linked USGS “Fact or Fiction” webpage does it mention the moon, planets or seasons, much less deny they have a relationship to earthquakes. Please provide evidence of your assertion.

    • Andrew Alden

      Thanks for pointing that out — I thought the page covered that topic. Here’s a better source, which points out that tiny effects of the Moon are sometimes found in earthquake studies, but even if you credit them as real they are significant only in a statistical sense, not a meaningful sense:


Andrew Alden

Andrew Alden earned his geology degree at the University of New Hampshire and moved back to the Bay Area to work at the U.S. Geological Survey for six years. He has written on geology for since its founding in 1997. In 2007, he started the Oakland Geology blog, which won recognition as “Best of the East Bay” from the East Bay Express in 2010. In writing about geology in the Bay Area and surroundings, he hopes to share some of the useful and pleasurable insights that geologists give us—not just facts about the deep past, but an attitude that might be called the deep present.

Read his previous contributions to QUEST, a project dedicated to exploring the Science of Sustainability.

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