By Xeni Jardin at 11:20 am Fri, Mar 11, 2011
High-rise buildings swaying during the 8.9 magnitude quake at Shinjuku, Tokyo, Japan on March 11, 2011. [video link]
It is of course actually mid rise buildings that have the most trouble with earthquakes due to resonance with their natural frequency.
I know this is what they’re designed to do in these circumstances, but it doesn’t make it any less terrifying for these monolithic structures we take to be so sturdy swaying like that.
The best way to understand why being rigid doesn’t work is to try building a model on a shake-table and seeing whether or not it works. You’ll find very quickly that it’s virtually impossible to build a rigid building which doesn’t come apart when it’s shaken hard enough. By contrast, designs which build in a little more flexibility so that they can swap do much better. Some science museums have earthquake exhibits where you can do this with building lego buildings on a shake table. It’s a lot of fun and very satisfying in gaining understanding. I highly recommend it if you have one near you.
Weeble’s Wobble, but they don’t fall down.
Don’t tall buildings also incorporate massive counterweights to counter the inertial forces and keep the towers relatively stable?
used to dreams of this maybe I’ll call them nightmares now
This is a -good thing- people. Buildings that don’t sway buckle instead.
I’m sorry, but what are you talking about? Couldn’t a building that doesn’t sway just, you know, be relatively still like the other buildings?
Couldn’t a building that doesn’t sway just, you know, be relatively still like the other buildings?
Seismic forces have to go somewhere. Earthquake-resistant buildings channel those forces into less destructive movement.
The building that is “swaying” is mostly staying still. It is the ground and the other buildings that are moving. The “swaying” building probably has shock absorbers.
Yeah, doin’ what they’re s’posed to do.
Still looks all wrong.
Exactly. They are specifically designed to sway that way in high winds and earthquakes. Precisely as planned.
God! It had to be scary to be in those buildings. Do you suppose furniture moved or is it bolted down like a ship at sea.
Still, it’s amazing that they withstood an earthquake of that magnitude! Hooray for engineers, remarkable materials and building codes!
Tall furniture sold in Japan usually comes with wall brackets to keep it from falling over.
probably the camera has an anti shake feature, plus it’s at ground level.
I know they are built that way – but holy shit!
There are some engineers/architects/building inspectors/red tape loving civil servants who seriously deserve props today. It’s hard to imagine that any other major city in the world could be standing after an earthquake like that.
To be fair, Japan is used to a lot of earth quakes and they know it’s not ‘if, but when’. It is a lot easier to enact regulations when the threat is real.
The largest known earthquake in North America was in Missouri, of all places, but I am sure places like California have better earthquake resistant buildings than the midwest.
That’s been my thought all day as well. To be able to take a 9.0 is seriously impressive – although I realize the epicenter wasn’t right in Tokyo. No matter what, tens of thousands owe those engineers/permit foks, etc. their lives.
If I remember correctly, a building sways a 1/2″ for every floor, and I believe that this means a 1/2″ in each direction. That’s why every high rise I’ve been in during an earthquake feels stronger and longer than the actual quake itself as the building is moving with the force instead of fighting it.
This was magnitude 5 in Tokyo which happens all the time. It was magnitude 8.8 at the epicenter, somewhere off the coast of Japan.
To put this in perspective yes there are earthquakes all the time, but yesterday’s was so big in Tokyo, the city shut down. So it wasn’t and “all the time” situation. The phone network shut down the big shock just after 2:45 pm due to the amount of people trying to use it, and then the roads as the 12 million people who live an work in Tokyo tired to get home without a rail system and the high speed road network. It took me 8 hours to complete a journey that usually takes 30 minutes, but I at least got home unlike a lot of people I know.
Yes there were no 30m tidal waves in Tokyo, but normal it was not. It’s gone on record as the biggest quake in the area of 1,000 years. And being in one of the buildings featured would see you suddenly on a ship on heavy seas, edging away from the windows as you have no way of knowing when the quake will stop and if the intensity will pick up.
Not saying it was normal, just that it wasn’t a “8.9 magnitude quake at Shinjuku.” It was magnitude 5 in Kanto. This quake was just very long.
I’ve experienced plenty of magnitude 6 quakes in Tokyo and yes, while you get shaken a bit if you’re in one of those high-rises it’s usually not life-threatening.
It was a 5 in Kanto on the Japanese scale of 7. The 8.9 number was the Richter scale. I can’t find a decent conversion between scales, but a 5 on the Japanese scale is higher than a 5 on the Richter scale.
I don’t know how strong is supposed to be “serious”, but there was a lot of shaking going on even by Tokyo standards. I’ve lived in Japan for 22 years, and that was the hardest quake I’ve experienced by a pretty fair order of magnitude. Windows broke, retaining walls fell apart in some areas, and things fell from shelves (especially on higher floors). Just because we’re all not trapped under piles of rubble doesn’t mean it wasn’t serious. It just means that the buildings are all pretty sound here and that Tokyo was “ready”. By far, the biggest risk aside from tsunami was the risk of fire, and my gas got shut off automatically when the quake happened. This is a mechanism that is in place to mitigate the damage of the quake, as is the shutting down of public transport.
It was bad, but I guess looking only at numbers and comparing areas of utter devastation, it looks like nothing happened in Tokyo. When you’re sitting in it, watching the ground ripple, the trees whip around, and the walls shake, it feels quite different.
The point I’m labouring to make is that those plenty of other quakes you experienced didn’t shut down Tokyo. This one did. All trains, all subways, all offices, all schools and all public buildings.
Obviously I’m exactly as aware of that as you are and fully agree with you. All I’m saying is that this wasn’t an extraordinarily strong earthquake _in Tokyo_. Some people make it seem like Tokyo is all but destroyed.
45 seconds of shaking is a long time….
When I stayed in Shinjuku about 5 years ago I went up to the observation deck of the Tokyo Metropolitan Government Building where I snapped this pic of a poster detailing some of the design features. Part of the first paragraph in English reads:
The flexible structure type “Rahmen (rigid frame) structure” method which is usually adopted in building ordinary skyscrapers would not ensure enough strength for this design, as the degree of bending in the case of earthquakes etc. would be too big. Therefore, the new Metropolitan government buildings, the rigid structure type “super structure construction method” has been adopted which is strong enough to resist any external forces such as earthquakes and wind by absorbing the force with a few gigantic pillars and beams.
I suspect the buildings in the video are of the first, more flexible, design if they’re the ones I recognise from my photos of the area. If so the TMGB towers above them and required the different approach. Whatever the case, they’re well aware of the environmental hazards that can occur and design accordingly.
Why is the camera not shaking?
The camera shook several times that I noticed, at least one of the shakes seemed to be an earth tremor.
Perhaps you don’t understand what you are seeing, though – when the earth moves beneath the buildings, instead of shearing off due to the tremendous weight above the plane of movement, the bottom of the building is moving while inertia holds the top in place. Then the top moves elastically, to get back into it’s proper place, and the whole building wobbles back and forth like a pendulum to dissipate the titanic energies involved.
To put it another way, if you bang a table that has a bunch of yardsticks superglued to it on end, the superglue will shear off at the base and the yardsticks will fall. If you superglue dixie-cups full of rubber to the table and plant the yardsticks on end in the cups, when you bang the table the yardsticks will wobble for several minutes but the glue bond will not break. Get it?
It’s possible that this film is showing the immediate aftermath of the quake, rather than the ongoing event. I think I saw at least one tremor though.
Because the buildings are swaying, not shaking.
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