Green Gabbro

Earthquake engineer Kit Miyamoto has posted a journal of his trip to Sichuan. If you don’t mind a little bit of construction jargon it’s a good discussion of the details of what kinds of buildings collapse, and what kinds are safe, as well as the logistical difficulties of the immediate post-earthquake recovery. The lesson to be learned from the Sichuan earthquake is the same as the lesson of basically every major earthquake in the past several decades: If you build bad buildings, they will fall down and kill people.

After some earthquakes, we have been able to dramatically improve our understanding of what constitutes a “bad building”. But in Sichuan – and Kashmir, and Bam, and Indonesia, and San Simeon, California – we already knew what was wrong. The real problems are social, political, and economic: We have lots of old buildings and can’t just replace them all immediately; good buildings cost more (though investments in seismic safety definitely pay off when the Big One hits); building codes aren’t always enforced the way they should be.

Instead of discussing these policy problems in detail, I’m going to spend the rest of this post explaining how relatively wealthy Americans can avoid buying or renting a piece of rubble in waiting. It is a delusion common to my social class that urging people in decent financial situations to make wise individual consumer choices is exactly the same as pushing for institutional change.

Really, though, it’s just that I’m in the middle of an apartment search myself. Mr. Man and I keep having the same conversation: Oh hey, hardwood floors… garden space for tenants… what’s the walk score?… AUGH NEVER MIND DEATH DEATH DEATH!

There are two types of buildings that provoke this reaction. Both are quite common in Seattle rental listings.

Old World Brick Charm

I am not sure what is supposed to be “old world” about the charms of Seattle’s older apartment buildings, but that is the consensus euphemism in this area for any rental property with any age-related quirk. Some of the units advertised with “old world charm” are actually charming, and they’re good from an urban design perspective as well.

In the eyes of a paranoid earthquake engineer, quaint old brick buildings look less like carfree-friendly architectural gems and more like a jumbled heap of bricks. Not just any jumbled heap of bricks, either, but a jumbled heap of bricks on your head.

Traditional masonry, or “unreinforced masonry” in modern engineering jargon, is made of layers of bricks glued together with mortar. There is nothing else connecting the layers of bricks; just mortar. This is fine until you start to shake the wall from side to side – mortar doesn’t put up much of a fight against this kind of motion, and as soon as one layer of mortar gives way, there’s nothing to stop the whole top part of the wall from falling off.

It’s like playing with traditional wooden blocks instead of playing with Legos.

i-117fabfd43941b31ac59003164e1450e-ReinforcedPocketCavityMason.pngNot all brick buildings are unsafe – modern masonry walls have steel bars threaded through them to hold the walls together during side-to-side shaking. On the West Coast, anything built after 1940 is probably okay. A report commissioned by the City of Seattle (warning, PDF link) provides a handy picture guide to some identifying structural features of unreinforced masonry buildings:

i-4925492e88673422480ab1c5d97d32c6-urm-identification.png
Image: ReidMiddleton

Retrofitting all the unreinforced masonry buildings in Seattle to a minimal standard of not killing people would cost about $400 million.

Modern Architecture

Here I mean Modern as in Modernism the popular post-WWII architectural style, not “modern” meaning “recently built”. I usually find this style of apartment building to be soulless and depressing, but the units are often practically designed and reasonably-priced. We found one Modern-ish triplex that was (and still is) not just practical, but actually quite charming, as the usual featureless boxes were arranged with something resembling texture. Plus, one of my nesting instinct daydreams is being able to lie in bed on a rainy day and watch the rain hit a skylight above me, and the place advertised “garden windows” that wrap from the walls to the roof in the bedroom.

There are three problems with this apartment. One is that windows often break during big earthquakes, even in modern well-engineered buildings. Waking up with a face full of broken glass is not fun. Another problem is that the apartment features a horribly cold and unfeeling generic-colored wall-to-wall carpet, and in order to protect the carpet, does not allow cats. The last problem is that Modernist buildings are not actually modern well-engineered buildings. In fact, there are about two decades of construction that are actually more dangerous than older buildings (except unreinforced masonry).

Two things happened to cause this. One is that architects and engineers discovered the wonders of concrete. Concrete is amazing – it will bear lots and lots of weight, so if you are clever, you can support the weight of an entire building with just one or two walls. This gives you lots of space for things like parking and big windows. Concrete is also horrible in the same way that mortar is horrible – it’s fine if you’re just resting a big load on top of it, but if you try to bend, twist, or pull on it, it breaks. Again, the solution is to pack the walls full of steel, but we didn’t figure this out until the early 70s (thanks in part to lessons learned from the 1970 San Fernando earthquake).

i-bafca231503f6d87f7918251f00b57f7-seattle-softstory.jpg The other thing that happened is that car culture came into full swing, and people started designing apartment buildings that sit on top of parking spaces. You see the spindly poles holding up the garage in this picture? They scare me. They might bear weight, but they won’t resist the shearing forces of an earthquake very well.

i-2728737eada15ed38253011a6bb0e353-soft_story.jpg When one floor of a building is primarily supported with pillars that don’t resist shear – perhaps because it’s a garage, or a retail store front with giant windows – that floor has an unfortunate tendency to collapse. You end up with buildings that look like they sustained very little damage… at least, until you count the number of stories and come up one short.

How Big a Deal Is This Really?

In any gathering of seismologists, you’ll inevitably find one or two who live in a ridiculously earthquake-unsafe building – or at least, I found that to be the case in the Bay Area. There are many appealing soft-story apartments in San Francisco, and other concerns – price, commute time, floor plan – can override safety. There’s a 2/3 chance of the Big One coming to the Bay Area in the next 30 years, but the odds of it happening during the 3-5 years you’re going to live in that grad student hovel are quite a bit less scary.

Seattle’s geological setting is still scary, but it’s not as scary as San Francisco’s. We’re looking at a few places this week that probably won’t throw any concrete or bricks at our heads, and might let us have a cat… but if those don’t pan out, I’ll probably relent and look more seriously at all those charming old brick buildings on Capitol Hill. After all, a long highway commute is dangerous, too. And carpets can harbor allergens, and if we have a nice kitchen we will cook more healthy meals full of vegetables, and and and… I minimize risk when I can, but life is full of tradeoffs.

Comments

  1. #1 Hank Roberts
    June 12, 2008

    Surely you meant ‘not as scary as Los Angeles’?

    San Francisco is going to get shaken, badly. Yes, the broken shards of plate glass piled ten feet deep in the canyons of the financial district is going to be impressive to the survivors who were smart enough not to run outside.

    And I do carry my Kevlar knit gloves for helping dig people out of that stuff, regularly.

    But, hey, LA and Seattle and Olympia are going to get shaken _then_stirred_.

    http://www.terradaily.com/reports/Supercomputer_Unleashes_Virtual_9_0_Megaquake_In_Pacific_Northwest_999.html

  2. #2 Coturnix
    June 12, 2008

    Are the things that make a building safe in earthquakes the same things that makes that building safe for hurricanes or tornadoes? How about wildfires and floods?

  3. #3 Eric Lund
    June 12, 2008

    Coturnix: Most things that improve the earthquake safety of a building will also improve its ability to survive hurricanes and tornadoes, but some different things are required.

    For most points east of the Sierras/Cascades (with the notable exception of the Mississippi Valley below St. Louis), there’s nothing wrong with brick: you won’t see earthquakes strong enough to topple the building, and they should be able to withstand hurricane force winds without problems. It’s more important to make sure the roof is properly attached. Too much glass is also a problem for wind storms of all kinds. You do not want to even consider staying in a trailer during a hurricane or tornado, but they will probably handle earthquakes OK unless something heavy falls on top of them. Being well away from the ocean is also a good hurricane plan: often along the immediate coast the storm surge will do more damage than the wind.

    For the strongest tornadoes (EF-5), there isn’t much you can do. The best plan is to be somewhere else when it comes through.

    For wildfires the formula is pretty simple. Wood is bad news (it burns), too much glass is bad news (it can shatter due to thermal stresses), most other construction materials are OK.

    For floods, the issue is not construction techniques but location. Make sure the basement doesn’t leak, but other than that, being on high ground always helps.

    Maria: Do my eyes deceive me, or is the house in the second photo leaning a bit to the left?

  4. #4 Maria Brumm
    June 12, 2008

    Eric, I think it’s the photographer who was leaning, and not the house. I can’t think of anything to add to your response to Coturnix, thank you :)

    Hank, San Francisco might not have problems from a basin effect, but San Jose will. Anyway, the reason I’m not as concerned about a Cascade megathrust event as I was about a Hayward rupture is that the Cascade events don’t seem to happen as often. Plus, there’s some ominous modeling work showing that the Hayward Fault has been loaded up by previous earthquakes. So even though a Cascade megathrust event might be much worse, a Hayward event is much more likely to actually happen in the next 3-5 years.

  5. #5 Lab Lemming
    June 12, 2008

    Won’t a megathrust be quite a ways west of Seattle? And what’s the point of engineering for long period earthquakes if you’re likely to get buried by lahars on a shorter timescale?

  6. #6 Maria Brumm
    June 12, 2008

    There’s enough basin amplification in the Puget Sound that a megathrust event is still a concern. Plus, there’s the Seattle Fault that runs through the south part of town.

    Hopefully Mt. Rainier will give us enough warning to evacuate. Earthquake engineering provides a big life safety payoff with fairly minimal structural improvement – not AFAIK the case if you’re trying to build homes to resist a volcano.

  7. #7 Silver Fox
    June 12, 2008

    Maria, thanks for the detailed and insightful post about brick and other buildings. I didn’t know brick buildings could be fixed (although, I guess money can buy you many things). There are a lot of old brick houses in the Reno area, which have long seemed ‘charming’ to me – except for the ‘bricks on your head’ problem.

  8. #8 Coturnix
    June 12, 2008

    Thank you!

  9. #9 Samantha Vimes
    June 13, 2008

    I worry more about that fault off the Washington coast than I do the ones in CA. We’ve generally been good about building codes and retrofittings, so while quakes are common, deaths are rare.
    But the underwater Cascade quake that’s expected to happen eventually will throw a tsunami against California’s shores. We definitely aren’t prepared for that.

  10. #10 Rich
    June 13, 2008

    “being able to lie in bed on a rainy day and watch the rain hit a skylight above me” sounds good at first, until it’s raining heavily as you’re lying there at 2am, desperatly trying to sleep before tomorrows big meeting…. Never again. Other than that I’m just glad I live in a relitivly uneventful(geologicly) part of the world. The question is that earthquakes are not exactly a new phenomena, so why has it taken so long for building standards to meet the requirments?

  11. #11 Andrew
    June 16, 2008

    Here is the Aristotelean physics of building standards: they have a lot of inertia, a lot of resistance, and not much impetus. When accelerated, for example by major disasters, they quickly resume their stasis. After 1906, the builders, papers and politicians all filled the echo chamber with talking points: the quake relieved all the subterranean stress, the buildings were well enough designed but poorly built, the real culprit was the fire, we need to rebuild ASAP. It took quite a while to improve the codes and enforce them. The one exception to this physics was in 1933 after the Long Beach earthquake, which destroyed hundreds of school buildings an hour or so after the kids had left for the day. A concerted public-education campaign by scientists and a progressive legislature got laws passed within a month mandating quake-safe public buildings. People keep trying to weaken them even today.

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