150 years after last big East Bay quake, what have we learned?

brick buildings help up with stilts

Buildings in San Francisco were damaged in the 1868 quake on the Hayward Fault. (Image courtesy of the Earthquake Engineering Online Archive)

October 21, 1868 – 150 years ago this Sunday — a walloping earthquake struck near Hayward, rocking the Bay Area and damaging buildings throughout the Bay Area and as far away as Hollister.

With a magnitude estimated between 6.3 and 6.8, it was the last big quake on the Hayward Fault, and its anniversary carries serious implications: Scientists think a big quake happens along the fault roughly every 150 years.

“Everything we’ve learned about the Hayward Fault tells us that the fault is ready to have another earthquake as big as 1868 today,” said Roland Bürgmann, a UC Berkeley professor of earth and planetary science and a member of the UC Berkeley Seismology Lab. “On average, we’re right at the time when the next earthquake would strike again.”

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UC Berkeley researchers have developed a walking tour of the Hayward Fault as it runs through campus.

The quake would be devastating. The Hayward is one of the most urbanized fault lines in the world, running from San Jose, along the East Bay hills and through San Pablo Bay, continuing under a different name, the Rodgers Creek Fault, north into Healdsburg.

But Bürgmann and other researchers at the Seismo Lab say that while there’s nothing we can do to prevent or predict big quakes, we understand the fault — and the risk — better than ever before.

“I do feel like, compared to many areas in the world, more is being done here to prepare,” he said. “But it’s never going to make us completely safe. The expected impacts of losses and economic effects are going to be great no matter how successfully we prepare.”

Berkeley News sat down with Bürgmann to talk about the threat of the Hayward Fault, 150 years of earthquake science and the best way to prepare for the next quake.

Let’s start at the beginning. A lot of people in California, when they think of earthquakes, think of the San Andreas Fault. What is the Hayward Fault, and why is it important?

Burgman stands with arms crossed

Roland Bürgmann is a professor at the UC Berkeley Seismology Lab.

The Hayward Fault is essentially the little brother of the San Andreas Fault. It is part of the San Andreas Fault system. In the Bay Area, the slip of the plate boundary is distributed between more than one fault. And as a result, the Hayward Fault has half as much slip as the San Andreas Fault, but that’s enough to make big earthquakes.

The Hayward Fault is considered to be the most urban fault we know of. Pretty much along the whole length it is very densely populated. Lots of hospitals and schools are very close by. It may be a smaller fault, but it’s much closer to people and therefore affects more people.

The last big earthquake on the Hayward Fault was in October 1868. How often do we think the big earthquakes happen on the Hayward Fault?

Back when it happened it was called “The Great San Francisco Earthquake,” until it lost that name to the 1906 quake. We actually know how often earthquakes on the Hayward Fault occur pretty well from geologic studies. And ironically for us now, it’s on average 150 years, plus or minus about 60 years.

Everything we’ve learned about the Hayward Fault tells us that the fault is ready to have another earthquake as big as 1868 today. But it could also wait for another few decades, or it could have happened already a few decades ago. But on average we’re right at the time when the next earthquake would strike again.

Are we ready for that?

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Bürgmann will give a lecture on the history of the Hayward Fault on Saturday

I think we are never really ready for a big earthquake. But there is a lot of effort being made to prepare by all of the local agencies and communities. There are very concrete planning exercises and earthquake scenarios to really assess where we have to focus and where do we get the most impact for the mitigation efforts we make.

I do feel like, compared to many areas in the world, more is being done here to prepare. But it’s never going to make us completely safe. The expected impacts of losses and economic effects are going to be great no matter how successfully we prepare.”

What more can we do? If you could wave a magic wand, what would you want to see governments or people do to prepare?

I think the most important efforts that have been made are long-term changes in building codes, encouraging retrofitting. For example, Berkeley gives you a tax break when you purchase a home that allows you to put money into retrofitting your home. I think things like that will really pay off a lot.

Just a few thousand dollars invested in strengthening your foundation and putting in shear walls can make a really big difference. It will save lives for sure, and it will also save significant amounts of money.

How did people understand earthquakes in in 1868? Did they understand the science of what was happening, or was it seen as a very unexplainable phenomenon?

In 1868, we knew almost nothing about earthquakes. They were considered to be more mythical events. Our understanding of earthquakes really improved or leaped forward after the 1906 earthquake on the San Andreas Fault, which let us understand that earthquakes occur along faults and that earthquakes happen again and again along the faults. Berkeley Professor Andrew Lawson led a massive 2-year long investigation that documented all the geologic and geophysical observations allowing for this breakthrough.

A wooden house is tilted off its foundation

This house in Hayward was shaken off its foundation by the 1868 quake. A repeat is expected roughly every 150 years. (Image courtesy of the Earthquake Engineering Online Archive)

What does the future of earthquake research at the lab look like? Where are we going in the next couple of decades of earthquake science?

We keep track of what faults do every minute of the day. We can see even the smallest earthquake on the Hayward Fault, and we can know what is occurring in real time at any time of the day, using satellites and whatnot.

We kind of have our fingers on the pulse of faults. What we want to figure out is if we can assess if a fault is getting closer to a rupture, if we can narrow our range of forecasting and better characterize the hazard.

Now, you’ll ask if we will be able to predict earthquakes. We don’t really see much likelihood there. But with ShakeAlert, or earthquake early warning, we can provide warnings within a few seconds to tens of seconds.

We’re not predicting the earthquake, because the rupture has already started deep in the ground, but with our instruments we know the shaking is coming.

I think that that will also make a real practical difference. We can slow down trains, open fire station doors so they don’t get jammed shut when the shaking starts or stop surgery midway through if there is going to be a big shaking event.

This always comes up when we talk about earthquakes, but say I’m a person who has always meant to get around to getting prepared but I haven’t. Where do I start?

Essentially people should think about what they should do at the moment that an earthquake strikes. The answer there is duck and cover to avoid being hit by things falling over. Preparing for that is just mental. You just have to think about it a little bit.

The second thing is to think about what you would need to live without power, running water or grocery stores for about three days. Somewhere in or near your house you should have water, food, batteries, anything that allows you to be quite independent for that amount of time. And you should have a plan for how you will communicate with people that are important to you.

There are little things too. I have a pair of shoes under my bed because one of the most common injuries is people getting out of bed after a quake and stepping on broken glass. Simple thing like that can make a big difference.

Now if you’ve done all that and you want to think bigger, then you want to not only think about being prepared for a few days but ask yourself what would you do if you didn’t have fresh, clean water or electricity for a week or several weeks? Or can you make an effort to retrofit your house to better withstand the shaking?

You know the really big quakes are actually quite rare, maybe in the Bay Area we’ll experience one or two in our lifetimes. So having little reminders in the form of feeling smaller earthquakes or “celebrating” earthquake anniversaries might just help us be a little more prepared.

UC Berkeley engineers discuss how they retrofitted Memorial Stadium to prepare for an earthquake on the Hayward Fault. (UC Berkeley video by Perla Shaheen)

Reporters interested in interviewing Roland Bürgmann can contact Will Kane at willkane@berkeley.edu