San Francisco Is Harnessing Public Pressure to Increase Seismic Safety

The most important thing a city can do to reduce its earthquake risk is to ensure its buildings meet a strong seismic code. San Francisco is rolling out new safety laws about soft story collapse, but not everyone is complying. In response, they're harnessing public pressure to help with enforcement.

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A sheared soft story of an apartment complex in the Marina District after the 1989 Loma Prieta earthquake. Image credit: USGS/C.E. Meyer

The Mandatory Soft Story Retrofit Ordinance requires retrofitting multi-unit soft-story buildings. The law applies to any multi-story wood-framed structure containing at least five residential units with a soft story built since 1978.

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A soft story is a floor level that is open with few internal walls like parkades and commercial spaces. The lack of internal walls means the structure cannot resist shear force very well, so are prone to collapsing during earthquakes. When the soft story collapses, everything above it also comes crashing down.

Soft story collapse during an earthquake engineering test.

Building owners had a full year to submit screening forms for the first step of the retrofit program. San Francisco had about 90% compliance, but that last 10% is about to get a lesson in enforcement. The city is mounting placards on buildings that haven't filled out their screening paperwork along with violation notices.

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Locations of buildings that did not submit seismic screening forms between September 2013 and September 2014. Image Credit: Screen shot of San Francisco Chronicle map.

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Where are the troublesome buildings located? The San Francisco Chronicle has an interactive map of all non-compliant buildings. Remember that these are just buildings where no one submitted a screening form; it has nothing to do with if these buildings need to be retrofit to meet the new seismic building code. But if you do live or work in these buildings, it's probably time to start asking about that form.

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The first floor of this building is composed entire of garages with few internal walls to resist shear. Consequently, the soft story collapsed during the 1989 Loma Prieta earthquake. Image credit: USGS/J.K. Nakata

Predictably, not every is happy about how public compliance is with the installation of placards. The LA Times writes:

"You're putting people in panic mode. That would be a horrible thing to put in a window. All you see is the words 'earthquake warning,' " said Huy Le, who owns a salon in the Castro District and leases space underneath a hotel. "It's almost as good as saying, 'Don't come into this building because it's going to collapse.' "

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Yet, that's exactly the point. The building owners that didn't submit their forms deserve to be called out: it doesn't matter if they failed to comply due to laziness, ignorance of the law, or the economic decision that paying fines was cheaper than retrofitting. Everyone who uses, or worse, lives in, a building that refuses to adhere to the new seismic codes has the right to know what's going on in order to balance their personal risk and make an informed choice.

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Between soft story collapse and liquefaction, the first and second stories of this apartment building completely disappeared. Image credit: USGS/J.K. Nakata

From here, building owners will need to either retrofit any building that needs it, or, if they choose not to retrofit, post a formal notice that their building may collapse during an earthquake.

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Illustration for article titled San Francisco Is Harnessing Public Pressure to Increase Seismic Safety

Spray paint marking beams for retrofitting plans. Image credit: John Stamets/Seattle Department of Transportation

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Retrofitting soft stories is relatively straightforward: add lateral structure to increase shear strength. The engineering solution is to strengthen existing walls, add new shear walls, or add a steel frame to critical areas. The choice of which technique is most appropriate depends on finances, safety, and building function.

And if they don't retrofit? At least you'll know when you're walking into a seismic timebomb.

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Good luck, San Francisco. You deserve to have strong building codes protecting you, and to have knowledge to make smart choices.

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DISCUSSION

a_blackpanther
a_blackpanther

Hah. Around here we have tons of buildings that are very old and susceptible to earthquakes, so a few years ago the municipality analyzed them and then placed "red dot" placards on the highest risk ones. There are several hundred. The owners don't have money to retrofit them, and the city doesn't either. So we have a city center full of red dot buildings (and some "impossible to classify" ones I'm side-eyeing). Some have been removed by enterprising residents who would like to actually sell their apartments. There were accusations of improperly placed placards just bring down property values.

This includes the old city center which is full clubs and terraces every night (buts oem of those have started collapsing by themselves already). But mostly everyone is twiddling their thumbs waiting for the next 6+ earthquake to hit. And it'll be soon and it will be a tragedy.

So I hope this works out for SF, because IMO 90% compliance is fantastic.