Was Western Washington’s infrastructure the reason the Nisqually quake had no direct fatalities?

Submitted by yungcarwashy t3_112pc1b in Washington

The Türkiye earthquakes were 7.8 and 7.5 respectively, and they’ve absolutely devastated that region. The 2001 Nisqually earthquake was 6.8 and yet not a single person was directly killed. Do earthquakes massively spike in lethality once above 7-7.5 on the Richter scale? I know for every 1 on the scale they’re 10 times more powerful, but is 7ish around the strength where things get extremely dangerous? If so, I am curious if the Nisqually earthquake will give our region a false sense of security. I worry as we are overdue for a substantial quake and the last one wasn’t as destructive compared to others around the world.

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PhuckSJWs t1_j8lieiu wrote

  1. Nisqually quake was deep (35 miles) and relatively "far away" from dense population centers.

  2. Seattle and Tacoma both have a lot of loose soils on top from when the cities were created (in Seattle's case when the hills were flattened), which luckily helped cushion the blow

  3. Even though many buildings were not earthquake ready, it is fair to say the majority here were likely more earthquake ready than most in Turkey

  4. Even for only being 20 years ago, we now have about an extra million in the metro area that were not here in 2001.

  5. Some luck

  6. Our big quake that we are overdue for will hit eventually. The Seattle fault is the one that will fuck us up if/wen it slips.

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normalabby t1_j8lqhqu wrote

Loose soil is typically bad for earthquakes, from what I've read. Is number 2 a guess? Or did you read something that said that?

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PhuckSJWs t1_j8lrncx wrote

we were far enough away, and across several fault areas, that the soils did dampen the shock wave somewhat in places by the time it got here.

that said, a strong quake near to Seattle (e.g., one on the Seattle fault) will likely trigger liquefaction locally in places due to strength AND proximity. that was not an issue with the nisqually quake. by the time the waves got here we got lots of shaking and damage to old infrastructure, but the skyscrapers handled it like they were designed, and for the most part we mostly suffered cosmetic damage and not a HUGE amount of infrastructure damage.

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normalabby t1_j8lsk2q wrote

But important to note there was liquefaction in SODO. It's a bit amusing to read this and think someone was surprised to find evidence of liquefaction in an area like SODO that is loose fill. It's a given, today. https://www.washington.edu/news/2001/04/17/damaged-chimneys-and-unexpected-liquefaction-from-nisqually-temblor-yield-earthquake-insights-uw-scientists-say/

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PhuckSJWs t1_j8lt7kl wrote

For sure, there WAS liquefaction, but it was very limited and low impact and almost entirely in the industrial areas south of downtown where it is mostly just garbage till soil on top of old tidal flats.

given the widescale "terraforming" the settlers did to the original Seattle hills to level out the city, it (liquefaction) was extremely limited in location and impact. we will not be so lucky with a closer and shallower quake.

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normalabby t1_j8lu7ng wrote

No disagreement on a differently located quake, just want to make sure we're not telling folks all the glacial till this region is built on is cushioning us. It didn't make the Nisqually less intense, the distance did. Someone would've felt the Nisqually more anywhere in the Puget Sound region that's on top of glacial till more than riding it out on bedrock, in the few places that exists.

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normalabby t1_j8lssc3 wrote

For how long the Earth has existed it's amazing how much our understanding has grown in just 70 years. Tectonic plates are a relatively recent discovery, thanks to ocean exploration.

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reroboto t1_j93u8vk wrote

I was at work in a building built on fill and it bounced rolled and cracked and we couldn’t go back for a month. Buildings in same area not on fill we’re fine

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SCROTOCTUS t1_j8odkgq wrote

The 9.0+ where it's like the whole region gets stuck inside a Shake Weight is not going to be a good time.

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iamlucky13 t1_j8prghz wrote

Because of the distance of the Cascadia Subduction Zone from Seattle, the local shaking will be more comparable to a magnitude 7 quake directly beneath Seattle. The biggest concerns for this quake scenario are the regional scale of the effects, and especially the dangers on the coast of the tsunami that will likely accompany it.

Here are the USGS predicted intensity maps showing this, as well as the 2001 Nisqually quake and the 2023 Turkey quake for comparison:

Magnitude 9.3 Cascadia Subduction Zone - Predicted - Modified Mercalli Intensity in Seattle 7 to 7.5

Magnitude 7.2 Seattle Fault Zone - Predicted - Modified Mercalli Intensity in Seattle 8 to 8.5

Magnitude 6.8 2001 Nisqually Quake - Modified Mercalli Intensity in Olympia: 6.5 to 6.8

Magnitude 7.8 Turkey 2003 Quake - Modified Mercalli Intensity: Over 9 in the worst affected areas

With that said, construction methods and quality matter a lot. The shaking in the Gaziantep, where a historically significant castle received major damage that has been shown widely in the news, the Mercalli Intensity is estimated at 6.7 - similar to what Olympia experienced in 2001.

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Norwester77 t1_j8ltqa0 wrote

I went on a city tour of Olympia (my hometown and the urban area closest to the epicenter), and the tour guide explained that the architect who designed a lot of the buildings in Olympia’s downtown core didn’t really know what he was doing and over-built everything, which has probably helped protect downtown against several quakes over the decades.

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yungcarwashy OP t1_j8lug6m wrote

Sounds like a happy accident!

On a real note, I think we need more engineers prioritizing overbuilding (not overcomplicating) rather than being so short-sighted. Would definitely pay dividends in the long-run in terms of maintenance and disaster resistance.

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Norwester77 t1_j8lv0iz wrote

We certainly had some damage: a major roadway along Capitol Lake collapsed, some large masonry blocks fell off the corner of an old bank building, and the Capitol dome was set rolling like a top on its base (at the time, it was held in place by gravity alone, but it’s since been pinned to the building)!

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minerkj t1_j8o8x6h wrote

The structural building code (the International Building Code, IBC) in Washington in general specifies what loads must be applied to a structure (earthquake, wind, snow) and how the structure must be adequate to withstand these loads and allow all occupants to escape after an event (eg earthquake).

An engineers gain nothing if a building is over- OR under- built, as they are paid based on a finished set of plans and calculations, so it isn't fair to say engineers are shortsighted. In contrast, the owners/developers of a building want to legally build as inexpensively possible (of course) because they are a business and they can absolutely be short-sighted, but the building code still requires all structures to be engineered to allow all occupants to escape.

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AlphaSquad1 t1_j8o1vqx wrote

That depends. You don’t want to overbuild just for the sake of overbuilding, that’s just make things more expensive needlessly. We still just want to design things to meet its expected requirements, you just want to expand what those requirements are. We would definitely benefit from more infrastructure being built to last longer and be more resilient. But here in Washington we don’t really need to build things to withstand tornadoes. There’s an old saying in engineering: “Any idiot can build a bridge that stands, but it takes a good engineer to build a bridge that barely stands.”

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ardesofmiche t1_j8lwwfw wrote

Earthquake scale is not a linear scale, so a 6.8-7.5 jump is not as small as it seems. It’s not a 10% increase in strength, it’s orders or magnitude stronger

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VGSchadenfreude t1_j8lofip wrote

Probably. We’re surrounded by fault lines and massive volcanoes, so we’ve always known that a disastrous quake or eruption is not an “if.”

It’s a “when.”

And that allows us to plan ahead and continuously improve our infrastructure.

That’s why, for example, despite the years of bickering over how to replace the Viaduct, the city still made sure to at least repair the Elliott Bay Sea Wall. That project was part of the same infrastructure package, but while the Viaduct replacement got bogged down, the Sea Wall forced ahead because that was the more important of the two.

We could live without the Viaduct if we had to.

But the Elliott Bay Sea Wall is the main thing stopping half of downtown Seattle from liquifying and sliding right into Puget Sound during the next quake.

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yungcarwashy OP t1_j8lracn wrote

What’s interesting is when that whole project was going on I never once read a news article about the sea wall, yet I heard dozens of stories about the viaduct… I was in early college and it makes me wonder if people only cared because it related to our automobile-centric infrastructure.

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VGSchadenfreude t1_j8lsfwi wrote

Wouldn’t surprise me, but there’s also the fact that the Viaduct was a lot more obvious and there was more arguing about it.

Nobody questioned the repairs for the sea wall.

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rourobouros t1_j8lo8w4 wrote

What PhuckSJWs said, and to amplify on the Turkiye/Syria (don't forget them) situation, the standard construction there appears to be unreinforced masonry (brick & stone). I think the places with the most casualties are smallervillages, not places with urban buildings of reinforced concrete. I suspect that those contractors being brought up on charges are responsible for a small percentage of the deaths and injuries.

But I could be wrong, we will learn more with time.

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yungcarwashy OP t1_j8lqx7b wrote

My apologies, Türkiye/Syria. Is there a name for this region that is more appropriate?

My coworker was arguing that those stone buildings have stood the test of time based on composition and appearance. My belief is that they could very well just be old architecture methods practiced in recent years with inferior materials.

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Theefreeballer t1_j8mvp9r wrote

Well I was in it , and was actually at my college library at the time and honestly it wasn’t that bad . I mean it went for a bit and it was aggressive shaking but none of the book shelves tipped over or I don’t even remember books falling from the shelves .

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Magrik t1_j8q3leb wrote

Sorry, I don't have a response specific to your question, just a reflection. This was the day I was heading off to Navy boot camp. If I recall correctly, I was on the road to the airport and didn't feel anything. We had to head to Portland the next day to fly out. Such a life time ago....

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Librekrieger t1_j8qck8l wrote

There was no single reason. It will take a detailed analysis and comparison to understand all the differences. In addition to other points made here, they happened at different times of day, and in Turkey there were aftershocks that were as bad as the initial Nisqually quake. And earthquakes are all different: some last longer, they cause different motion (up/down, sideways, rotation).

But you can see for yourself that they were just vastly different phenomena. The Nisqually quake caused visible cracks that were maybe a meter wide. You could hop across from one foot to another. The one in Turkey caused visible rifts the size of a large river, dozens of meters wide in places.

https://www.insider.com/turkey-earthquake-olive-grove-deep-chasm-split-2023-2

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Wellcraft19 t1_j8qhisl wrote

Turkey’s earthquake was far stronger than anything we’ve seen here. Building standards are vastly different here. Modern residential buildings in our region are lightweight rigid (wooden) boxes, vs Turkey’s heavy (poorly assembled) brick and concrete buildings. Those building are too heavy for rigidity, and to frail for any flex. For larger/taller buildings here, ‘sway’ is designed in to them so the entire building is to survive a tremor ‘giving’ (although unlikely any 9.0 that there are talks about).

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IntheOlympicMTs t1_j8uvf2e wrote

Earthquakes are measured on a logarithmic scale. That said I was on I5 driving by exit 104 in a pickup and didn’t even feel it.

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