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San Francisco’s Seismic Gamble (nytimes.com)
310 points by montrose 9 months ago | hide | past | web | favorite | 202 comments

There are always ways to build the tall buildings safely- they're just more expensive. These buildings aren't unsafe because there's no choice, they're unsafe because the builders wanted to save money and the building code was too loose to stop them.

Japan is a highly volitile region, tectonically speaking, yet they've managed to build lots of tall buildings safely. How? By having some of the strictest building codes in the world, yet allowing development within those rules.

Meanwhile, outside of SF itself, the Bay area refuses to build any real density that's desperately needed, using earthquakes as (one of many) excuses for NIMBYism and entrenched interests of landlords.

As an architect in San Francisco, I would definitely prefer to be in a modern high rise here over other buildings for safety purposes during an earthquake. I am highly skeptical of this article as I have in depth knowledge of seismic engineering, the building code and the updates after every earthquake around the world to the code and engineering practices.

The leaning building across from my office, for example, has nothing to do with seismic issues but basic design/engineering/construction flaws in not extending the pile footings deep enough to solid ground as others in the area have such as the new Salesforce tower.

Your comment seems to echo that of another architect quoted in the article.

Ron Klemencic, the chief executive of Magnusson Klemencic Associates, the company that did the structural engineering for Salesforce Tower, says he agrees that water and sewage systems need higher strength requirements, but not high rises. “Buildings falling on top of other buildings — that’s not going to happen,” Mr. Klemencic said.

They never explained why Klemencic's reasoning. Care to explain why "buildings falling on top of other buildings — that’s not going to happen"?

Hollywood treats falling buildings like falling trees [1]. The building basically gets cut off at the base, then stays together as it falls to the side until it hits the ground. I'm no expert, but IRL I think any significant amount of lean would lead to massive structural failure in your average skyscraper. Once the structure starts to fail gravity is going pull the pieces straight down since nothing is pushing them to the side. It's certainly a danger to surrounding buildings (see the WTC) but vastly different from buildings falling over on their sides to crush their neighbors.

1: https://youtu.be/r0tgEYiTNd4 (0:35 and 0:45)

My understanding is that the way buildings collapse in Hollywood is not how they collapse in reality. If the base of the structure begins to fail, it doesn't fall over as a tower, but crumbles into itself.

The Twin Towers took out the blocks surrounding them. Literally they fell on top of other buildings, even though they "collapsed into themselves."

I am very skeptical of anybody, no matter how experienced, that gets on the news and says "that'll never happen," regardless of what the "that" is.

Has he considered a skilled terrorist cell lacing only the east side of Salesforce Tower with explosives?

With the Twin Towers, the issue wasn't so much that they fell on top of other buildings (they didn't - you can see that on footage of them coming down), it's that when they hit the ground, the debris cloud billows out at high velocity and consists of projectiles that can structurally damage neighboring buildings. All that gravitational potential energy of the structure gets converted to kinetic energy as it collapses, and that kinetic energy is basically like a bomb going off at ground zero. When a bomb goes off near a building, the building is gonna have a bad time, even if it doesn't directly hit it.

Like I said, it's like a bomb going off at ground zero. The pictures you link support that: notice how the damage is mostly near street level (from projectiles moving outwards from the crash site) rather than at the top of the building (from projectiles falling on the building).

Even blowing out only one side of a tall tower, would not cause it to fall like timber. Instead, one of two things will happen. If there is low lateral strength (unlikely), the east side of the floors above will shear and collapse off, straight down into a pile on the east side. If there's good lateral strength, The forces formerly supported by the now blown east structures will largely fall on the adjacent structures around the building, overloading them, causing failure, and rapidly continuing around the supports in a zipper-failure, whereupon the above structures now unsupported again fall straight down with gravity's vector.

Either way there's probably a bigger pile on the east side, but it's not like the top floor of a 1000' building will land 1000' laterally from the base. 100' would be a long way (tho there's be lots of flying debris for a good distance).

Skyscrapers have a tremendous amount of mass and are engineered to resist the force of gravity. That's hard, so they only bother to engineer it so that it resists that force in one direction relative to the building.

As soon as you might start to turn the building onto its side it falls apart like a sand castle. Were this not to happen the building would have to be engineered such that it could withstand being turned on its side like that without collapsing. But they don't design them as such.

Wouldn't there be bigger concerns, terrorist attacks really don't happen that often.

It'd be like constantly worrying about protecting yourself from lightning.

>It'd be like constantly worrying about protecting yourself from lightning.

A lightning rod (US, AUS) or lightning conductor (UK) is a metal rod mounted on a structure and intended to protect the structure from a lightning strike. If lightning hits the structure, it will preferentially strike the rod and be conducted to ground through a wire, instead of passing through the structure, where it could start a fire or cause electrocution. Lightning rods are also called finials, air terminals or strike termination devices.

In a lightning protection system, a lightning rod is a single component of the system. The lightning rod requires a connection to earth to perform its protective function. Lightning rods come in many different forms, including hollow, solid, pointed, rounded, flat strips or even bristle brush-like. The main attribute common to all lightning rods is that they are all made of conductive materials, such as copper and aluminum. Copper and its alloys are the most common materials used in lightning protection.[1]


You're right, but over the course of a building's lifespan, the "chance" is greater, right? So the chance of a terrorist attack against salesforce tower this year is less than the chance it might happen sometime in the next 30 years. I'm not good at statistics, though.

Anyway, this is why we have a lot of earthquake preparedness, though the chance is 5% in the next 30 years.

It's not a "constant worry," so much as a plan. There's non-negligible chance of terrorist attack, so they architect in such a way to prevent it being catastrophic. There's a non-negligible chance of your office catching fire, so they put green exit signs at the door. That sort of thing.

> though the chance is 5% in the next 30 years.

Not even close. USGS estimates over the next 30 years are: 72% probability of a M6.7 or higher 51% probability of a M7.0 or higher 20% probability of a M7.5 or higher

Source: https://pubs.usgs.gov/fs/2016/3020/fs20163020.pdf

And?? California building codes have improved alot since the 1980s or so. I remember the 1989 LA earthquake as I drove through the aftermath to visit my grandma about 2 weeks after, I live on the Central coast.

All in all not since 1933 has CA lost more than 100 lives in an earthquake: https://en.m.wikipedia.org/wiki/List_of_earthquakes_in_Calif...

That tells me our building codes are pretty damn good.

I work at ucsb and the catilina islands recently had a 5.2 about 2 weeks ago and the building shook abit. But all in all unless we suffer an 8.0+ I'm not terribly worried (knock on wood). To put that another way, realistically for any moderate sized earthquake CA is generally well prepared in terms of architecture, unless the big one hits ... In which case just kiss your butt goodbye.

I do wish, even for the big one, that CA invested in an early warning system like Japan has ... Imagine a 5-50 seconds warning of an earthquake, that would save lives, not stricter building codes: https://youtu.be/OXXZouxPT7U

Here is a better, live example of the early warning: https://youtu.be/n-FMpNBfna8

An early warning system might be nice, but stricter building codes are what is going to save lives. Japan has those too.

It's also worth pointing out that there has arguably not been a large quake close to a major city center in California since 1906 (for some values of "large" and "close"). The 1994 Northridge quake, which did some $15B in damage, was probably the best recent preview we have. Loma Prieta certainly did serious damage, despite being (as I recall) some 75 miles from San Francisco.

The real test is when the Calaveras Fault that runs up the east side of the SF Bay breaks. The last time was 1868, when there wasn't much there; estimated magnitude was 6.3 to 6.7. A quake of that size on that fault now — and it's getting to be likely, in the next two or three decades — is going to make a hell of a mess. We'll find out then how well a lot of things hold up.

Earthquakes are interesting, I was mostly talking about terrorist attacks, which are basically rounding errors when compared to other causes of death.

I don't think it would cumulatively add up to much, but would love to see the math.

I don't agree with Klemencic on this - given a big enough earthquake with large enough building sway (imagine a tower being a vertical beam with the base fixed and the top swaying back and forth) the structure can fail such that the momentum of the building during maximum sway will either break the building and/or cause the building to impact other swaying buildings.

Simulation showing an actual building failure from the NZ Christchurch earthquake [1]. It collapsed in the Feb 2011 Christchurch earthquake, magnitude 6.2[2].

Once the building's supports fail, it drops rather than topples.

[1] https://www.youtube.com/watch?v=TCJq_2-q34k [2] https://en.wikipedia.org/wiki/2011_Christchurch_earthquake

That's a squat cube-like 5 story building. You're probably right, but that video alone doesn't convince me a skyscraper would necessarily fail in the same way.

It wouldn't. The are designed to withstand hurricanes. It takes extensive preweakening to bring one (or three) down.

People are more likely to be killed by flying glass in the Financial District than skyscrapers collapsing. A good approximation of how far glass can be thrown downtown is roughly 2x building height due to the winds coming off the bay.

Is that supposed to make it better?

I have friends who unfortunately got to witness what happens when plate glass comes down. They can barely talk about it. It also means that the injured and trapped folks in the high rises are going to be without aid in buildings with dead mechanicals for awhile.

I think he's saying, in an earthquake, stay inside.

A lot of people think running into the street is what you wanna do. It is, in like, Mountain View maybe. Realistically you want to just jump under the nearest thing you can and hope for the best. If you're in the Financial District in the middle of the street... well your friends apparently have seen what that'll look like.

Right, that was the point I was trying to make, perhaps I didn't state it well. Seek shelter immediately and try to avoid flying glass. I would also avoid UMBs (Unreinforced Masonary Buildings) these buildings WILL collapse. They aren't as common in FiDi but are all over Soma, Chinatown, and the Tenderloin.

Yeah. Lots of stuff comes from above if you are on the street. Going inside a building is a good bet.

"35 deaths and many injuries from falling masonry during the 2011 Christchurch earthquake. Buildings with dangerous parapets, facades and verandahs" [1]. That was 20% of total deaths.

Certainly near a skyscraper, you want to go inside, since if it pancakes, being outside won't help anyway - debris will hurtle horizontally.

[1] https://www.stuff.co.nz/business/71738867/property-council-s...

> like, Mountain View maybe

During the Loma Prieta Earthquake a bunch of my coworkers fled the building and took shelter in the parking lot under the power lines.

> The leaning building across from my office, for example, has nothing to do with seismic issues

Nowhere in the article did anybody make such a claim. It was to illustrate the general problems of building in that area even without an earth quake, which leads me to the other point, what IMO is the main issue, and I think is pretty independent of how much effort is spent on any one building: The potential for soil liquefaction. They included several maps showing that many of the tallest buildings are built pretty much exactly over ground that might suffer that fate in a big earth quake. How would any individual design help? Compared to the alternative of not building the tallest structures right over those spots. The maps also showed plenty of more solid ground, but that is where there are mostly lower buildings.

I would like to hear your opinion on that issue.

As for your doubts on the entire article, it seems to me they asked quite a few specialists? Are they all mistaken?

Well, I certainly would like you to be right, I used to live in SF and I still love the entire greater Bay Area.

Liquefaction mitigation is possible (ground replacement cells, compaction grouting, etc). It costs a lot and the only place that we (my company) have done true liquefaction mitigation is on large state funded jobs. The preferred alternative for the Bay Area is to sink foundations through liquefiable soils, discounting any strength from these soils, and rely on empirical studies that have found that liquefaction does not necessary result in loss of confinement which would induce buckling failures in the piles.

I share the GP's doubts on the article. The practicing specialists they talked to certainly don't think there's a gamble: they actively pursue and design sky scrapers in the City. I think their words are being misused in a way that makes them seem like they agree with the article's premise.

A modern high rise- but only as long as you are confident there were not basic design/engineering/construction flaws?

Which, for those of us who are not structural engineers and cannot review the work to see that it is indeed well done...

If the earthquake were large enough, could the Millenium Tower completely fall over? Or is it only destined to keep leaning?

High rises in general are designed to sway in an earthquake - that sway absorbs the horizontal forces being applied - similar to a tree. If an earthquake gets sufficiently large, say larger than any known measured earthquake to date, that sway differential would increase enough that buildings would either hit each other, or the building would sway beyond the ability of the structure to recover and fall over. A standard approach for tall buildings is to incorporate either a dynamic weight high in the tower to counterbalance the sway so it doesn't go critical, or incorporate dynamic elements in the foundation system. In general, if a modern high rise is falling over, all buildings without the benefit of this level of modern engineering have already fallen over.

> A standard approach for tall buildings is to incorporate either a dynamic weight high in the tower to counterbalance the sway so it doesn't go critical, or incorporate dynamic elements in the foundation system.

As a structural engineer on the west coast, I can say that neither of these are standard. Tuned mass dampers (TMDs) are commonly used for reducing wind-induced vibration, but not for seismic applications. Nor have I ever designed, seen, or heard of 'dynamic elements in the foundation'

The reason you can't rely on TMDs is because they are tuned to a structure's elastic period of vibration. That is to say, the materials are still in their elastic range. When a ductile structure is subjected to a sufficiently large earthquake, elements of the seismic force resisting system (SFRS) will yield. Hence the period will elongate. Hence the damper will be detuned and may not provide any benefit at all.

A link to the next generation TMD's to handle earthquakes: tuned mass blocks, orthogonal poles, and torsional pendulums (TMDPP) : https://www.hindawi.com/journals/sv/2017/5834760/

1) I'm not saying there aren't novel solutions - there's a whole category of devices that use active control. I'm saying its not common place.

2) From what I understand, China has a completely different design philosophy. They design structures to remain elastic, under certain earthquakes, which would then allow for TMDs.

I think he is referring to base isolation which, I agree, is non-standard.

I meant standard for the really big buildings under the highest stress. For lesser challenges, agreed, non-standard.

They don't base isolate tall buildings, they isolate short ones. The whole point of base isolation is period elongation. In a tall building, you're already flexible, and your column loads are tremendous. It makes no sense.

Would you be able to provide an explanation of what a dynamic element in the foundation is, for example?

In mechanical fields, dynamic means "moving". The weight literally moves, so it's dynamic. Another YouTube video that explains it a bit better: https://www.youtube.com/watch?v=f1U4SAgy60c

See how a dampened dynamic build vs a regular dynamic build react to movement (and you can imagine the static build): https://youtube.com/watch?v=xp2pGxFzrzI

>Apologies for the complaint, but could someone please let me know why I'm being downvoted for this question?

It's likely because you're implying "dynamic" is a "buzzword" in a discussion about structural engineering and seismic movements (which is, by definition, a dynamic system).

But I'm not, I was saying that due to my background, I can't help but think dynamic is a buzzword. Therefor I was asking someone who was clearly knowledgeable on the subject to set me straight.

The "why"s (your prejudices) are irrelevant.

Also I don't really think there's a background you can have where you don't understand, or cannot lookup, the difference between dynamic and static if you really cared to understand. Seems more like self-important rhetoric than anything.

I don't think linking it to a buzzword adds anything to the conversation. The question didn't need a justification.

All right. I've removed it. Such is life

What is your background?

This gets at my concern though - it is not that we don’t know how to build skyscrapers safely. It is that there is now positive evidence that those construction and engineering techniques are not being applied properly, at least in some cases.

For me, the question is not about whether high quality projects are going to be okay. The question is: on what basis do I believe there has been sufficient oversight to guarantee the soundness of new construction?

I can remember talking to SPUR members in 2001 about how problematic it was to extend downtown development into SOMA, etc, due to liquefaction and uncertainty. When the building craze hit, it felt like it brushed these concerns aside, rather than answer them. Now we have leaning buildings that don’t meet basic construction requirements. It doesn’t inspire a lot of faith.

Are design parameters such as pile depth part of the public record? Is there a way to lookup the design of a building?

Most cities keep a set of permit drawings, but generally you need to have a proximate relationship to the building to get access to them

The leaning building across from my office, for example, has nothing to do with seismic issues but basic design/engineering/construction flaws

You say that, and then you claim that seismic engineering is free from such flaws? That seems a bit like hubris.

Seismic is different than basic construction. That building tilt would have happened anywhere vs. in an earthquake prone zone like SF.

Japan and California are pretty comparable in terms of science and engineering for earthquake resistance. There are some differences on the public policy side, which influence how the engineering requirements are implemented, but Japanese buildings are not intrinsically safer. Note that the 1994 Northridge (Calif.) and 1995 Kobe (Japan) earthquakes were about the same side - the Japanese quake was ~10x as costly and ~20x as deadly (mostly due to population density around the epicenters).

Isn't there is a slight difference - the maximum expected Japanese earthquake (9.0) magnitude is much more powerful than the maximum expected California earthquake along the Calaveras/San Andreas (8.0)? Cascadia looks to be another 9.0 fault line but the epicenter would be closer to Seattle/Portland than California.

Building standards were first implemented in Japan in 1952 and were revised in 1981 and 2000. Apologies for not having an English source, but of the people who were killed because of the house or building that they lived in, 98% were living in a building/house that did not meet the standards of the 1981 revision to the building codes.


Yeah. While I don’t support NIMBYism, YIMBY-types seems to love to use Japan as their counterexample, without understanding that Japanese homes tend to be built somewhat dangerously and without regard to earthquake safety.

How would you build to withstand against soil liquefaction? It could be likely that Tokyo is built on more stable bedrock.

My understanding (probably naive) is the footings driven into the ground are deep enough to go below this area and rest on stable rock.

That’s how it was explained in a documentary about mission bay (south of AT&T).

edit: For those interested, this documentary explains the approach https://www.youtube.com/watch?v=SyjijQS2dAk&t=1219s

Do you remember the name of this documentary? A quick search didn't turn up anything. I live in the area and would love to learn more about this.

I recall seeing some computer animation to this effect in a documentary (in the UK) about the Millennium tower tilting - searching on that brought up some confirmation in the form of a press release by the TJPA:


The 60-story Millennium Tower is made of concrete rather than steel, resulting in a very heavy building. This heavy structure rests on layers of soft, compressible soil. The foundation of the Tower, however, consists only of a concrete slab supported by short piles that fail to reach the bedrock below. That foundation is inadequate to prevent settlement of a building with the weight of the Tower. In contrast, the Salesforce Tower and 181 Fremont Tower, also adjacent to the Transit Center, are supported on piles drilled down to bedrock. Millennium Partners’ poor design decision is the cause of the tilt and excessive vertical settlement of the Millennium Tower.

Sure, at about the 20:00 is when they discuss Mission Bay specifically. The whole documentary is solid though if you have more time. I learned a lot and found it very fascinating.



> The 2011 Great East Japan Earthquake caused the severe liquefaction of reclaimed lands in the Tokyo Bay area, from Shinkiba in Tokyo through Urayasu, Ichikawa and Narashino Cities to Chiba City.

Those aren't the parts of Tokyo with skyscrapers.

Most of Tokyo comprises low-rise (1-10 story) buildings.

Which parts have the tallest buildings?

Either go deep enough to hit bedrock or design your building to float. They both work fine, it's just a question of cost.

Well, option #1 is to build somewhere else. Is every square foot of SF subject to liquifaction? Or is it just the cheapest piece of ground? Is it that the local government has zoning rules that simply prevent development and density in the places that would be safer? To be clear, I don't blame developers for finding the cheapest option- that's how capitalism works. It's up to governments to make the rules such that the cheapest options are also the best ones.

Second, is there anything that can be done such that the soil won't suffer from liquifaction or will to a lesser degree? Probably expensive to do, yes, but surely there are means.

And there's probably a million other ideas that might work that I don't even know of. It's silicon valley, that's where ideas come from, right? "Impossible" usual gets San Francisco types all excited.

There's a downvoted reply to my original comment saying that I haven't actually tried to build these- and they are correct. I'm not a civil engineer. But I am a firm believer that if you make strong regulations and enforce them, clever engineers always find a way, at a cost. But the hard part of that isn't the engineering, it's having the political willpower to enforce strong rules.

Japan is always touted for this, but Chile (Santiago, Viña) are similarly plagued with extremely large earthquakes, with regular occurrence over 7.0, and you see tons of mid-rise buildings in Santiago. The building standards there are exceptionally high after the 1985 earthquake (8.0). If Santiago and Viña del Mar can do it, surely San Francisco can.

Also, If I recall correctly, what did the most damages in the 1906 SF earthquake was not the actual earthquake itself.

What caused the most damages was the fires after the earthquake.

Hopefully SF has a better fire department now than in 1906.

Going a bit deeper, the earthquake took out most of the water supply to the fire hydrants in the city, and so the fire department couldn't put out the fires that started during the quake.

As a result, SF now has a backup hydrant system! Those big fat multi-colored hydrants are all connected to a fire-only water system that's gravity-fed from cisterns all over the city. The colors of the hydrants encode information about which cistern the water comes from, IIRC. And whenever you see a random arc of a circle made of brick inlaid in the road, that's outlining the location of a cistern.

https://www.atlasobscura.com/places/the-golden-fire-hydrant https://www.citylab.com/design/2017/05/the-sublime-subterran...

I don't have the link handy, but I was reading an article about how the backup water system is inadequate for the western part of the city (Sunset district mostly) and they're figuring out now how they want to extend it.

I recall reading an article from a year or two ago stating that a lot of those cisterns are empty, and the overall backup water supply is woefully insufficient.

San Francisco has 66 fire trucks the last time I checked (I’m an SFFD volunteer). If there is a bad enough earthquake they will not come for you. The sheer volume of fires and service response calls will overwhelm them. It is your responsibility and the responsibility of volunteers in your community to make sure everyone is safe or triaged correctly the first 2 days (7 days better) after a disaster.

Neighborhoods will definitely burn but containment will be more of a factor of how windy it is and how easy it is to get to water.

> If there is a bad enough earthquake [the fire department] will not come for you. The sheer volume of fires and service response calls will overwhelm them.

Wish your comment was higher up.

If you're in the Bay Area: sign up for a NERT/CERT class, buy an ABC fire extinguisher, and know where and how to shut off your gas line. Assume the fire department will not get to you.

SF NERT: http://sf-fire.org/neighborhood-emergency-response-team-nert

If there are wide spread fires all around your building, I don't think small extinguishers from few uncoordinated volontaries would help.

In such event, I would do only one thing: run.

Fires start off small then grow. If you have a fire in your home and can put it out early by yourself, that's the best scenario.

I'm not advocating for anyone to run around playing fire fighter.

Many 1906 SF fires were intentionally set by the owners themselves, after the earthquake had damaged their buildings, because most insurance policies covered losses due to fire, but not those due to earthquake. So, if you burned your building down completely, leaving no evidence that it had been first damaged by the earthquake, you had a chance at being reimbursed. http://www.sfmuseum.org/1906.2/arson.html

It's not clear how much of the fire damage was due to intentionally set fires; there were also a significant number of fires started unintentionally when the fire department dynamited various buildings in failed attempts to establish fire breaks. (And, hey, you were still covered if your building was dynamited!) So, lets hope the SFFD is better in this regard than in 1906 as well.

The insurance industry claims that only 2% of the destruction was directly due to the earthquake; 98% was from the fires. https://www.iii.org/article/san-francisco-earthquake-1906-in...

It's not just the fire department that's better - in 1906 a lot of those fires were caused when the quake would pull a gas appliance from a wall and leave a gas leak that later ignited.

Nowadays everyone has their hot water heater and oven bolted or strapped to the wall. I'm sure there are other useful fire codes California has adopted since then but this one rule will probably prevent more fires in the next big quake than any other.

My LA house has to have a shutoff that automatically kills the main gas line during an earthquake. One must be installed when the house changes hands. No grandfather clause exception allowed.

yes, i'd forgotten about those; we got one installed at our house a couple years ago, iirc at no charge from PG&E. it's definitely better/safer than the per-appliance solutions.

Additionally, gas fittings that are designed to (safely) breakaway are more common.

same thing for Kobe in 1995. Fires were responsible for most of the deaths.

> These buildings aren't unsafe because there's no choice, they're unsafe because the builders wanted to save money and the building code was too loose to stop them

Side note from a New Yorker, it always shocks me how careful San Francisco pretends to be with building codes and environmental and safety reviews and this and that, only to go on and systematically approve a series of terrible structures. (Not before showering them with ecological awards, of course [1].)

[1] https://en.wikipedia.org/wiki/Millennium_Tower_(San_Francisc...

I can't remember an article were an architect or engineer flat-out claimed that the Millennium Tower design was fundamentally flawed. I thought this article had such a quote but reading it again the claim is merely implied by the journalists.

The Millennium Tower was not flawed. It just unfortunately bumped into the law of large numbers. Even if all future towers in SF rest on bedrock, that still wouldn't reflect poorly the judgment of the Millennium Tower architects.

Frankly, New Yorkers should be more concerned about the seismic safety of New York buildings. In terms of seismic risk vs seismic structural resilience, New York may be facing a great chance of catastrophe than San Francisco.

New York also almost had a skyscraper blow over because no one bothered to calculate what the wind hitting it diagonally would do: https://en.wikipedia.org/wiki/Citigroup_Center

Regarding Japan: Nara has the Okumura Commemorative Museum [1] that has a bunch of little exhibits demonstrating how Japanese builders have been adapting to earthquakes. You can even look under the building at the foundation to see two of the methods in action - a crazy sort of "rubberized" slide pillar, as well as pillars just plonked on top of plates of teflon.

[1] https://www.okumuragumi.co.jp/en/commemorative/index.html

>How? By having some of the strictest building codes in the world, yet allowing development within those rules.

While this tends to be true for large, commercial architectural projects, it’s not true for residences. A big reason why almost no one buys used homes in Japan(and if they do, they tear them down and build new) is that building codes are very loosely enforced in this domain. If I remember correctly, structural calculations to resist earthquakes aren’t even required for buildings under 2.5 stories (i.e. just about all private residences).

It’s a commonly-cited misconception that zoning is what makes housing so cheap in Japan. Zoning is a factor, but in reality it’s because housing is built pretty fast and loose as a disposable commodity.

One of the reasons why it's harder to buy some used homes in Japan is because it's harder government backed housing loans for housing that do not meet earthquake standards. For older buildings it's also harder or not possible to get tax breaks.

I see things like this ("These buildings aren't unsafe because there's no choice, they're unsafe because the builders wanted to save money and the building code was too loose to stop them.") posted by people on HN quite often. As someone who has worked in the Bay Area on buildings, I read things like this and laugh. They come from a place of ignorance - anyone who thinks the building code is "too loose" has never successfully engineered something which complied with it.

A code can be both too strict and too loose but for different aspects. The article makes clear that the building code trusts skyscraper developers much more than makers of smaller structures. E.g., "A five-story building has the same strength requirements as a 50-story building."

The obvious counterproof to your argument is Millennium Tower, a 60-story skyscraper, which has sank at least 16 inches so far. Most of those one 1 side, so the building now tilts at least 15 inches at the top: https://www.bloomberg.com/news/articles/2017-02-01/who-will-...

They are still trying to figure out how to fix it. Doing so could cost well more than it took to built it in the first place. One proposed plan is to anchor it to bedrock on the low side, then let the tower sink further until it's about even before anchoring the other side: https://sf.curbed.com/2018/4/16/17242450/millennium-tower-si...

I honestly think it's reasonable that the building code gives skyscrapers a lot of leeway. Traditional building codes are very prescriptive, and that works better with (common and similar) houses than (rare and varied) skyscrapers. But the ongoing clusterfuck that is Millennium Tower makes it clear we can't just trust developers to get it right. As mabbo says, they have a strong financial incentive to cut corners.

Why would the strength requirement for a 5 story building be different from a 50 story building? Do the building materials behave differently when you increase a number?

The Millennium Tower is not a "counter proof" to my argument, although it has become a bellwether for exactly the kind of posters I call out in my original post. My argument is that people on here who do armchair structural engineer and make comments like "the building code is too lax" are ignorant and full of shit. All the Millenium Tower proves is that, even with a building code, it is still possible to get unintended consequences. To the rest of your post about skyscrapers getting a lot of leeway - they don't get any more leeway than any other structure, they just have the money it takes to invoke portions of the code that allow alternative analysis methods. It just doesn't make sense financially to do some of the complex modeling for a 3 story building to shave 5% of material costs.

If anything, the building code is more stringent on skyscrapers because it does require more advanced analysis. This analysis is NOT precluded for smaller buildings, it is just not worth the money.

> Why would the strength requirement for a 5 story building be different from a 50 story building?

Because if it falls over it won't just kill 5 stories worth of people, but 50 stories plus an unknown number of people in the building it falls on, as well as creating a giant civic problem?

> ignorant and full of shit

Oooohkay, buddy. At best you are playing semantic games here. If your theory is that the building code is just fine when things like the Millennium Tower can happen, then we disagree on what "fine" means.

> If your theory is that the building code is just fine when things like the Millennium Tower can happen, then we disagree on what "fine" means.

What portion of the building code do you think needs to be updated in response to the Millennium situation? In reality, the building code achieves a success rate far in excess of what engineers deem acceptable. It is unfortunate that the Millennium is a big glaring exception, but the fact remains.

Geotechnical engineering (the cause of the Millennium lean) remains a highly empirical field of engineering with uncertainties that dwarf structural ones. Hence there is a lot of built-in conservatism in design parameters like bearing pressures. But there are limits to the amount of information you can ascertain of what's below you that you cannot see. Looking back in retrospect and saying "well obviously they should have had longer piles" like many people have on the various threads about the tower is a pretty ignorant thing to say, and it shows that they do not have an appreciation of the engineering behind the decision. There a tens of thousands of examples of friction piles that have worked flawlessly. The engineering evidence appears to have supported the decision, but the in-situ soil conditions varied from their design model. This, in my opinion, is not a failure of codes, but an unfortunate, statistically rare outcome.

Engineers may deem this acceptable, but given that San Francisco taxpayers may end up footing the bill, I doubt the rest of us do.

I understand that the people who built it believed that they were doing just fine. But I also understand that there are enormous pressures to keep costs low on a project like this. The notion that for this building those enormous pressures had exactly zero contribution to this outcome is a claim I certainly wouldn't accept without evidence.

If this were really in the range of statistically expected outcomes, then a) there should have been a plan in place to fix it before the structure went up, and b) they would have had sufficient insurance coverage to pay for the fix. Neither is true. The ongoing gosh-golly-who-cooda-node routine plus the simultaneous festival of blame-shifting suggests to me that, at best, the business side of the operation went well beyond what an engineer would have done in the same place.

The correct fix to the building code here I'm happy to leave to the experts, just as long as they eliminate outcomes like this. If that ends up raising the costs for other fancy buildings stuffed with pied-a-terres for the wealthy even to prohibitive levels, I am entirely fine with that. Erring on the side of of earthquake safety while building near major faults in major metropolitan areas seems like a great choice to me.

> just as long as they eliminate outcomes like this

I guess the point I'm trying to make is that complete elimination isn't possible in a long tail statistical distribution. There will always be a point where we have to draw the line, and there will always be freak occurrences of undesirable outcomes. This is the crux of engineering - finding the correct balance between cost and safety. Perhaps the current state is not enough, but the wildly disproportionate amount of structures that are working just fine tells me we are close.

> If that ends up raising the costs for other fancy buildings stuffed with pied-a-terres for the wealthy even to prohibitive levels, I am entirely fine with that.

Building codes aren't only applied to high end buildings. Any changes affect the (badly needed) low end housing just as much as high end buildings. Just another thing to consider.

> Erring on the side of of earthquake safety while building near major faults in major metropolitan areas seems like a great choice to me.

No disagreement there ;)

The outcome I'm referring to isn't just the sinking building. It's the clusterfuck of a sinking building and years of chaos that could spill over into extensive costs for others. Long-tail outcomes perhaps can't be eliminated, but they can be 100% mitigated through planning and insurance.

Medical care has a much longer tail, for example, but many countries manage to provide full financial coverage and individual support in treating and managing even very rare diseases.

If you're saying this was a reasonably forseeable but unlikely outcome of cost-driven skipping out on the bedrock anchoring that neighboring buildings used, the I don't think it's too much to ask them to have an answer to the question of, "Ok, if your cheap solution doesn't work, what will you do next?" And if they don't have a good answer to that, I also don't think it's too much for them to not be allowed to build the thing.

Your comment would have more gravity if you pointed to specifics instead of touting some vague credentials and telling other people they're wrong.

> more gravity

Now that would be a serious problem.

>> anyone who thinks the building code is "too loose" has never successfully engineered something which complied with it.

Perhaps, but have you compared it to the building code in Japan? I personally have qualifications in this area so I'm just asking.

Too late to edit. Why oh why did I omit the word "don't" in front of "have qualifications"? It was meant to be an honest question to fill a gap, not a weird confrontational thing.

Shallow dismissals make you look like you have nothing to say. The article posits one thing, then the OP gave a concrete example clarifying why one region is having problems the other doesn't. You then come in and just claim that the building codes aren't actually that loose while jerking yourself off about your experience in the matter, despite the article's position on unsafe buildings and the OP correctly pointing out that a region with similar problems doesn't have an issue with its high rise buildings that they allowed to be built.

Do you have anything else to say besides vague claims on your credentials and experience?

I don't doubt you but could you elaborate? Thanks.

The fact of the matter is in a best case scenario, 10% of these buildings are going to collapse in a major earthquake. 10% of the newest, shiniest, up to code buildings. Best case, that's the engineering code, that's the spec. They are designed to collapse 10% of the time.

In reality many more will collapse, because some buildings are older and not up to code, as well as earthquakes generally just being weird and unpredictable.

Do you think 10% of buildings collapsing is a "loose" or "tight" code? 10% losses is acceptable in say, human habitation?

That's not how tolerances work.

You don't get exactly 10% failure rate, you have to demonstrate better than 10% failure rate which means going past that point. Further, failure is not 'collapse' failure is anyone in the building being unable to exit safely.

And again, they are aiming for a 9.0 that's a ridiculously large earthquake. An 7.8 similar to the last SF earthquake would still be a major earthquake, but vastly less dangerous by comparison.

Weird that the word "Japan" occurs 0 times in an article about skyscrapers and earthquakes.

I realize the focus of the article is SF, but when the author elaborates on our lack of experience with skyscrapers in earthquakes, with no mention at all of Japan, it makes me think that this is just a clueless scare piece rather than any kind of thoughtful analysis.

Funny, earlier today I just happened to see this Tokyo earthquake footage of skyscrapers swaying violently:


Then, in the article, I read about San Fransisco:

"the issue of seismic safety of high rises was “never a factor” in the redevelopment plans"

I can not imagine any positive outcome here.

> Funny, earlier today I just happened to see this Tokyo earthquake footage of skyscrapers swaying violently

It's unclear from your comment, so I wanted to clarify for other people who may not know: skyscrapers are intentionally built such that they sway, as that helps to disperse the energy more than a rigid structure.



I'm sure the New York Times has a vested interest in keeping New York the economic powerhouse of the United States and this article directly attacks San Fransisco's best option for economic growth.

There are entire careers dedicated to determine buildings ability to survive natural disasters and informing people about the risk. There are entire careers dedicated to finding ways to make buildings more earth quake resistant. It seems like banks, developers, governments, and insurance companies would be listening to both of these professionals very closely before building something one thousand feet high. I would prefer to hear from them than Thomas Fuller of the New York Times.

Those of you actually living / working in the Bay Area, I highly recommend looking into "NERT" - Neighborhood Emergency Response Team[1].

It's about 18 hours of training on disaster preparedness, earthquake safety, triage, and search and rescue. The idea is twofold - the more citizens that can handle themselves and their families for the first 72 hours of a disaster, the more people that have a 72 hour timeline to death (trapped, injured) the professionals can find and rescue.

The second is that there is literally no city in the world that has the fire department resources to handle a catastrophic disaster (>8 earthquake, tsunami) without "significant loss," and so trained volunteers can do a great deal to "fill the gap."

In the 1989 earthquake untrained volunteers were critical in helping the SFFD get water into hoses [2] when the mains went down. Last count I heard is that there's about 2,000 NERTs now trained in the city. Imagine having 2,000 basic-trained volunteers helping out in a disaster. Incredible. To put it in perspective, there's only about 1,500 employees of the SFFD.

There's a city-wide drill this weekend, actually, and they need victim volunteers. If you want to get painted with gruesome injuries and scream at people in green hardhats, it could make for a great time! [4]

If you aren't in the bay area, check out the FEMA equivalent, "CERT." [3]

[1] http://sf-fire.org/neighborhood-emergency-response-team-nert

[2] http://cdn.abclocal.go.com/content/kgo/images/cms/349779_128...

[3] https://www.ready.gov/community-emergency-response-team

[4] https://www.eventbrite.com/e/victims-needed-volunteer-for-th...

edit- by the way, this training is free, and comes at no obligation to actually run into burning buildings should a disaster happen (they want you to take care of your home, family, and neighbors before anything else)

"Right now the code says a structure must be engineered to have a 90 percent chance of avoiding total collapse. But many experts believe that is not enough.

“Ten percent of buildings will collapse,” said Lucy Jones, the former leader of natural hazards research at the United States Geological Survey who is leading a campaign to make building codes in California stronger. “I don’t understand why that’s acceptable.”"

One way that reads to me is that an event over some threshold has a high probability to cause the complete collapse all of those buildings. 90% doesn't seem like a very high threshold either, if it corresponds straight out to a 1-in-10 event that seems quite bad. If it's a 90% chance of survival in a 1-in-100 event, that's better, but not great.

Current building codes are intended to design to a 10% probability of collapse in the "Maximum Considered Earthquake", which is roughly a 2475-year event. The 2475-year event has a 2% chance of occurring during the (assumed 50 year) lifetime of a building.

>the (assumed 50 year) lifetime of a building

what happens afterwards? is the building supposed to be torn down?

Nah, the building is (mostly) just as good at the end of that time. It's just a convenience to make the probabilities easier to conceptualize. If we designed buildings such that the design earthquake had a 5e-6 daily chance of occurring, we'd just be confused.

This reminds me of my favorite unit of measurement: https://en.wikipedia.org/wiki/Micromort

If there is a 10% chance of collapse every 2475 years, that is ~1.1/10million per day chance, or 0.11 micromorts. That assumes 100% death during a collapse, and that the person spends all day in one of these buildings.

0.11 micromorts/day is very low, which makes the design criteria reasonable. Of course, I suspect our ability to predict infrequent events with any degree of accuracy is unlikely.

I suspect it would be the latter, similar to other disaster planning.

This gets you into that domain where most people really don't like to go, but... you don't get the choice of 100% perfectly likely to stand up, so where do you draw the line? You don't have an alternative. A line will be drawn. If you don't draw one deliberately, you'll draw one accidentally.

But if you want to have some fun with ways the probability estimates could be badly broken, correlated failures can be the way to go. Suppose for the sake of argument that there is an earthquake in the future that if each building was subjected to it individually would cause 10% of the buildings to come down. That doesn't mean that 10% of the buildings will fall down in real life, though, because the failures could be correlated and coupled, if one building falling down makes another building falling down more likely.

If I'm running the physics and numbers in my head correctly [1], even in an extremely large earthquake the Hollywood image of buildings toppling each other like dominos is still exceedingly unlikely. They'll go down, not sideways. But the additional shocks they create in both the air and the ground in the process could tip some other buildings over the edge. We know from 9/11 that buildings going down can seriously damage other nearby buildings.

So, densely packing buildings with a 90% survival rate can result in a net survival rate less than 90%.

And of course, if it's 90% at Richter x, there's no law of the universe that says x is the limit. x+1.5 is still perfectly possible.

[1]: It's hard to google up the amplitude of an earthquake in a distance measure, rather than Richter scale or something. But it looks like "several centimeters" of transverse motion would be a very large earthquake, which isn't going to put the center of mass of a building out of the area described by its foundations. Which isn't anywhere near a complete description of what it would take to tip a building like a domino, but is enough to say it's a long way from happening.

(My guess is that it's actually impossible to tip a tall building like a domino as any possible attempt to exert the forces necessary to do so would itself be enough to destroy the building. See also "why Superman must also be telekinetic", because it doesn't matter how strong you make an 747, there is no place on that plane it can be picked up by any amount of pressure exerted by two human-sized hands without the hands tearing right through the plane, rather than nicely carrying it. (A handful of non-telekinetic Supermans could do it if the plane lowers the landing gear and Supermans support the tires with their backs instead, but that'll be tricky to "fly" in other ways. Especially since the best way to support the plane will be with the Supermans being sideways, to maximize area of contact with the tire.) Similarly, some sort of Superman-esque force that applies equally to all atoms would be required, rather than the real forces we can apply via external pressures.)

x+1.5 is possible, but super unlikely at the upper end of seismic events. Given the way the Richter scale works though, even x+0.1 could be devastating.

It's the latter, 10% collapse in a 1 in 100 event. I used to do similar work in floodplain management. I don't even know what a 1 in 500 event is in earthquake terms, is it even possible to build something that withstands that level of quake?

This got me wondering what the Salesforce tower’s builders countermeasures were for the soil and seismic issues. Surely they tried to do something.

Here’s an article about what they did. (Skip the fluff in first third, it does get down to details later.)


Because of soil issues, the Transbay Terminal (Salesforce) builders had to anchor the foundations in the bedrock, which is unfortunately deep under layers of landfill and soft sand. But this fill and sand is exactly what will get liquified during a big one, so they didn't have much choice.

But what's weird, IMO, is that some of the shorter highrises like the Millennium Tower were approved to be built not anchored, but on pylons floating in the soil layer:



I mean, sure, as long as things are stable, the weight of the building will keep it in place. But I don't think anyone knows how the soft layer underneath most of SOMA will behave, when a big earthquake comes. People know it will undergo liquification, but by how much, and what will it do to buildings on "floating" foundations, that's not certain...

You assume, based on the journalists' innuendo, that friction piles are per se not seismically safe. That's wrong. Friction piles are well studied and used for tall towers in seismic zones all around the world, including Japan.

That the Millennium Tower is sinking asymmetrically doesn't necessarily mean the design was flawed, even in a high-risk earthquake zone. It could be flawed, but the very fact that it's sinking doesn't tell us that. It could merely be that out of the hundreds of towers constructed globally each year, Millennium Tower was the unlucky outlier which defied the otherwise carefully weighed odds.

From the diagrams included in that link, it looks like there's going to be a real problem if "the big one" happens during severe gusting winds.

Even if that isn't the case, the Millennium Tower is literally across the road[1] and could fall in the wrong direction considering "Millennium Tower has sunk almost a foot and a half and is leaning 14 inches toward neighboring high rises"

[1] https://www.google.co.uk/maps/place/Millennium+Tower+San+Fra...

Is 14" of lean a lot on a high rise? Certainly that is a small fraction of a degree of total lean.

The sinking does seem like a concern and is no doubt related. It seems like someone underestimated how much foundation work would be needed on that building.

How does the front door work? Do they have steps down into the lobby now?

How many inches of lean can a building support before it just falls over WTC style?

A really long way. The center of mass has to move past the edge of the base for something to fall over. I can't find how big the Millennium Tower is to work it out, but I'd guess at least 30 feet.

> at least 30 feet [of lean]

I'm pretty sure the building would have lost structural integrity from the force applied by gravity before the lean can reach 30 feet.

The lean of the leaning tower of Pisa is nearly 13 feet. The millennium building is over three times taller than that.

I this "lean" is measured at the top, and the buildings weight is equally distributed from top to bottom (i.e. its centre of gravity is right in the middle) it can lean half its radius until the CoG is no longer above its support and it should topple.

That's very rough of course. Many bad things could happen much earlier, such as unexpected forces causing structural damage.

Note also that the WTC didn't exactly "fall over". It collapsed on itself.

> before it just falls over WTC style?

The WTC did not fall over.

"Witnesses on the morning of April 18, 1906, described the city’s streets as rising and falling like a ribbon carried by the wind."

"one out of every four buildings in the Bay Area might not be usable after a magnitude 7 earthquake"

"At a time when the average price of a home in San Francisco is above $1.2 million..."

Why aren't people pricing in an earthquake discount? This is so totally irrational, housing in SF should be cheaper given the certain risk of an earthquake and consequent large probability of severe damage. And even if your house isn't destroyed, good luck finding a contractor post-earthquake. Even now contractors are so hard to find, over priced, and many do shoddy work, I can't imagine why people don't see this coming and stop paying this much for something that may fall down any day now.

> Why aren't people pricing in an earthquake discount?

Similarly why we continue to build in floodplains, it's usually fine and when it's not the Federal government steps in and makes sure people are bailed out. This has proven to be a good strategy as long as you're not in Puerto Rico. It's the same idea as the "Greenspan put" being priced into the financial markets.

> when it's not the Federal government steps in and makes sure people are bailed out.

This may be a conservative talking point but it seems more likely that such disasters happen on timescales humans aren't built to reason about. Even if there were no bailouts I doubt things would be any different. These areas have desirable attributes that make them attractive regardless of the risk. There are also precious few areas not subject to any risk at all (a large portion of the continental USA is subject to hurricanes, tornadoes, earthquakes, blizzards, or other potential disasters).

> Why aren't people pricing in an earthquake discount?

Because it's a matter of insurance, and thus reduced to a recurring premium bill.

Why not price all maintenance costs and electricity too? Living in this house for the next fifty years will cost you all these utility bills; you should get a discount from the purchase price to reflect that! :)

Few insurers offer earthquake insurance, and those who do charge very hefty premiums, we're talking about adding 50% to the cost of your mortgage over 30 years. Hence, a very small portion of the housing stock in SFBA is insured against quake damage.

I still want to know why people aren't thinking about this when they pay so much for a house.

Lol nobody has earthquake insurance. It's exorbitantly priced.

11% of homeowners have earthquake coverage in CA.


Like all insurance, the price reflects the risk vs the number of buyers. If more people had it, the price would be less exorbitant.

I'd think that 11% of CA homeowners is large enough that you have already hit the economies of scale and the price is largely a factor of risk. Quintupling that number is not going to reduce the price.

The number won't quintuple unless the price is reduced. Of course if 89% of the people were cheerfully willing to pay what the 11% are paying, then the price wouldn't change. And in that imaginary world, 89% would be covered.

The question is why don't the insurance people work a bit harder to broaden the coverage; they could make more money even at a lower price point.

Perhaps, those who are not covered are too resistant; they are not willing to get the coverage even at a reasonable price because of the way they perceive the risk/benefit. So that is to say, maybe it's a "hard sell".

Love every opportunity to link to this story: http://www.slate.com/blogs/the_eye/2014/04/17/the_citicorp_t...

The Citigroup building in NYC had a fundamental design flaw that could cause it to collapse.

That story is pretty well known in Engineering circles - we used it as an ethics case study at my Australian University.

Apparently South Michigan is the safest place to live from natural disasters: https://www.quora.com/What-is-the-safest-place-to-live-in-th...

IIRC, Las Vegas is also pretty high on that list, hence the data centers.

That's just a random Quora user's opinion. Southern MI sees plenty of powerful tornados. For instance https://en.wikipedia.org/wiki/1980_Kalamazoo_tornado and https://www.weather.gov/grr/1965PalmSundayTornado

I know what your saying but all I could think of was Flint.

> The goal of the code, say proponents of a stronger one, should be the survival of cities — strengthening water systems, electrical grids and cellular networks — not just individual buildings.

I'm not sure how you'd prevent water & sewer lines from breaking during an earthquake - they're surrounded by earth (or secured along concrete walls in buried vaults) so they're going to get motion & shear all along their length - so not much room to flex. Assuming they were made of a flexible material and not cast iron.

One of the reasons why the 1906 earthquake was so devastating were the fires afterwards, where the fire companies couldn't get water.

After the 1906 earthquake, SF started adding large, distributed cisterns to store water throughout the city. I'd imagine there are lots of similar sorts of tweaks you could make - more a focus on a distributed, resilient grid than preventing pipe breaks entirely.

Even in 1989 they couldn't get water, they had to suck it out of the bay.

That appears to be part of the water supply plan (makes a lot of sense to use the water they've got there), and the cistern system appears to have partially functioned: http://www.sfmuseum.net/quake/revawss.html

> The upper zone of the AWSS, however, functioned normally through the earthquake period, and was used to suppress earthquake-caused fires.

Looks like they're building more: http://abc7news.com/news/over-30-cisterns-to-be-built-in-sf-...

Of all the natural disasters, I seem to shudder at earthquakes the most. May be because I am biased by witnessing the destruction brought by the 2001 earthquake in India. The thought that at any moment, without warning, the safe abode you are in might come crashing down on you is pretty scary.

I wonder with human population increasing and with the shortage of urban land needing highrises, what is the long term solution to this.

The long term solution would be having enough energy to modify the earth enough in order to prevent earthquakes.

From http://mkaku.org/home/articles/the-physics-of-extraterrestri... :

"For example, a Type I civilization is a truly planetary one, which has mastered most forms of planetary energy. Their energy output may be on the order of thousands to millions of times our current planetary output. Mark Twain once said, ”Everyone complains about the weather, but no one does anything about it.“ This may change with a Type I civilization, which has enough energy to modify the weather. They also have enough energy to alter the course of earthquakes, volcanoes, and build cities on their oceans."

It seems a lot easier to build floating cities than to cool Earth's core enough to stop earthquakes.

That would be a very stupid thing to do because it would also stop the Earth magnetic field which helps to shield us from cosmic radiation.

When we have the technology to cool Earths core(!), we'll also be able to make our own magnetic field.

Stopping plate tectonics also has longterm consequences for the deep carbon cycle and climate which we'd better be prepared to handle. Though we probably have to tackle that particular problem way before.

I did not ay cool earth's core, not did Michio Kaku. Given the amount of people living near fault lines, certainly we should be able to manage e.g. magma flows/ pressures in an ideal, long term future.

Great/Scary article. Has anyone worked in the tilting building? Are there cracks in the walls? Is the soil compaction expected to stop (some max density type thing)? I think they stopped the tower of Pisa tilting by injecting concrete under it. It must be difficult to not exasperate they problem at the start of the injection (I am guessing they have to remove some material first).

I knew someone who lived in the building, and while she didn't report cracks in the walls, she did say that things would reliably roll toward one corner of her apartment if they weren't secured.

14 inches over 58 stories works out to 0.10 degrees. That doesn't seem like enough to make anything roll. You might have to shim your billiard table.

Your math is wrong. The relevant angle is not 14 inches over 58 stories, it is 14 inches over the horizontal length of the building.

I'm not sure what this. Guessing maybe 120 feet, e.g., gives a tilt of 180/pi * arctan(14/12/120) = 0.56 degrees.

Sorry, you are the one with the wrong math. The building is out 14 inches at the top. You divide that by the height to get the angle. What you calculated is the lean for a building which sank 14 inches on one side. That would be way worse - an excursion of [edit] 6 feet at the top.

A golf ball sounds like something to me:


Your floor being on a 0.1 degree slope is a rise of 0.2 inches over 10 feet. Definitely noticeable.

Not definitely. The professional standard for levelness in homes and office buildings is F_L ~ 20, where F_L is the levelness "F number".



The maximum slope b=rise/run compatible with this is b_max = (314 mm/3m)/F_L = .105/F_L ~ 0.005 for F_L = 20,


which corresponds to 0.005 radians = 0.3 degrees.

Projects like roller rinks and warehouses that use air pallets require more level floors, but typically only by a factor of 2 .

Very one sided article and full of scaremongering.

There is no comparison with building codes of other countries which are earthquake prone (such as JP or TW), only example is provided (Millennium Tower) and it is unclear if liquifaction will only affect skyscrapers or 1-2 storey buildings too.

>Previous earthquakes have revealed flaws with some skyscrapers. A widely used welding technique was found to rupture during the 1994 Northridge earthquake in Los Angeles. (Many buildings in San Francisco and Los Angeles have not been retrofitted.)

That statement really boggles the mind.

How do you own some of the most valuable property in the world, and not maintain it in the simplest of ways against something that could literally destroy your investment? After 24 years of knowing that your building was in danger?

I thought the massive water tank at the top of One Rincon Hill , to control swaying in the event of earthquakes, was interesting: https://www.sfgate.com/bayarea/article/One-Rincon-tower-feat...

Straight from the article:

> The damper system has no connection with the seismic safety of One Rincon. It is always a challenge to build a tall structure in earthquake country, and One Rincon's engineering response was to use outriggers, tall reinforced concrete columns built around the core of the building.

> For years the city restricted building height to 500 feet in most neighborhoods.

Surely that’s a typo? Because that is kind of insane.

That's 150 m, or around 40 stories - that's pretty tall for outside the centre of a city.

Why? That's about a 50 story building.

Yes, which is way higher than I'd expect, given SF's general opposition to high-rises. According to Google, the actual limit is 40 feet.

Example article I found: https://recklesslyoptimistic.com/san-franciscos-height-restr...

Here's another article cutting a height restriction near 500 feet.


There are probably more height restrictions in different areas, and a 500 foot limit is actually quite restrictive. It would have prevented Salesforce Tower. The Empire State Building is over 100 floors.

Yeah, if the limit were 500 feet you wouldn't have builders constantly complaining about it.

Because “for years” that was the restriction. That doesn’t sound like much of a restriction. The implication is that it’s restricted less now. The story talked about how San Francisco resisted high rises for a long time, so that restriction doesn’t follow the story — that’s why I think it’s a typo.

It's not an if, it's a when. You couldn't pay me enough to live in SF.

This presentation is absolutely fantastic. Hard to remember a better example of digital journalism well used. No gimmicks - just relevant information intuitively presented. Excellent!

My mileage aired from yours: I would have been happier simply wth pitctures rather than something that hijacked the scrolling and interrupted the flow of reading. Reading on an iPad fwiw.

I actually went and tried it out on an iPad too. I admit it's not as nice an experience - in fact it almost seems buggy, scrolling up past the top of the viewport before the JS notices and suddenly pushes it back down. They could improve that. At least make it less jarring.

Reason no. 42614 not to live in the San Francisco Bay Area.

Don't live in Houston because hurricanes and flooding.

Don't live in New York or Chicago because cold.

Don't live in Seattle because rain.

Don't live in Taipei because earthquakes and a bunch of cruise missiles pointed at it.

Don't live in Seoul because artillery and a dictator across the street.

Don't live in Miami because hurricanes.

Don't live in Madison, WI because tornadoes.

Don't live in Hill Country because ambulance will take 20 minutes to get to you when you step on a rusty barn nail.

Cold and rain seem like they don’t belong on that list unless you’re homeless.

There is a reason I moved from cold and rain to an earthquake risk city.

Some people will take death over ever having to shovel again.

>Don't live in Hill Country because ambulance will take 20 minutes to get to you when you step on a rusty barn nail.

is that bad? it's not like you're going to die from tetanus in 20min.

ok fine, heart attack

SFFD has a 6 minute response rate within San Francisco.

That is why a huge number of people in Hill Country have helicopter insurance. It they have a medical emergency a helicopter will land on their hill and fly them to a medical center.

Seattle has an equivalent risk of earthquakes due to the Cascadia fault

42615, you might end up working with Salesforce.

I'm chiming in late in the game here, but what's wrong with Salesforce? (Only reason I ask is because of the piece that I just saw on 60 minutes Sunday night, so your comment piqued my interest)

Development in a web browser. Everything is paginated. A bastardiation of Java and SQL - without joins as the language it uses. An over complicated data model (for the business I had to integrate it with at least. Some things could only be done via SOAP.

I had to integrate our existing Django based system with Salesforce. What I expected to take a few days took a few months. Similar syncing of data between another Django based system did take a couple of days.

I can't go on, it brings back too many bad memories. If you have ever enjoyed development you will hate Salesforce. It feels like the tech equivalent of digging holes and filling them back in again.

It's slow AF.

Basically ever database SaaS tool is slow AF. They don't tell you that during the sales cycle though


as fuck

Maybe so, but please don't post unsubstantive comments here.


It seems shockingly irresponsible that it is allowed to build high rises in areas that can undergo liquefaction.

No matter how strong the building is if the ground gives up it must fall over.

Blame zoning!

Shockingly, the people who own property less likely to collapse in an earthquake do not want big buildings next door. So big buildings are being built on harbor fill. What could go wrong?

IIRC the proper way to handle that is by anchoring the foundation of the building to the bedrock underneath the layers which can undergo liquefaction. That's done by means of drilling as deep as necessary to put the foundation and then adding pylons on which the building rests.

Depending on how deep the liquefaction-prone layers go, that's could be an option that's realistic only for a high rise.

And how does that relate to Millennium tower which has already "sunk a foot and a half"?

What if high rise building is anchored through all liquefaction-prone layers but the layers start to shift (they are on slight incline) when they get liquified? I am not expert but I can imagine it is possible that, if the structural support is long enough, just few inches of lateral movement may completely compromise the support.

Because the millennium tower did NOT do the correct thing, and did not anchor it to bedrock.

They would be having problems if they did it the right way.

Or you can design the building to float on the liquified soil. Either way works.

Shameless plug: At my company, tensorflight.com, we use computer vision on satellite/aerial/street view imagery to extract factors used for predicting the earthquake damage. For example, construction type or the number of stories mentioned in the article.

Given factors extracted by us, to get the full picture you may use open source catastrophe modelling software, Hazus released by FEMA.

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