How Telescopes Deal With Earthquakes In Chile

Reader edgeofphysics provides a technical sidelight on the earthquake in Chile this morning — some details on how the European Southern Observatory protects the mirrors of the Very Large Telescope when an earthquake strikes. "Given that Chile is one of the most seismically active countries in the world, how do astronomers protect their giant telescopes that have been built or are being built in the Chilean Andes? This blog post discusses how Chile's most advanced facility protects its priceless 8.2-meter primary mirrors in the event of an earthquake."

Comments

Bubble Wrap?

[WrongSizeGlass]

Lots and lots of bubble wrap?

Re:Bubble Wrap?

[sopssa]

Lots and lots of bubble wrap?

Which have been all popped by the scientists.

VLEC - Very large egg cartons

[syousef]

Pity they don't protect the servers against being slashdotted.

Re:VLEC - Very large egg cartons

[Anonymous Coward]

The primary mirror is 18 centimeters thick. Because of its weight, the mirror’s precise shape can warp when it is tilted, so 150 actuators, upon which the mirror rests, continually push and pull at least once a minute to ensure that the optimal curvature is maintained. More impressive than the actuators are the clamps around the edges of the mirror, which can, at a moment’s notice, lift the entire mirror, all 23 tons of it, off the actuators and secure it to the telescope’s support structure in case of an earthquake (moderate quakes, of less than 7.75 Richter, are not uncommon here, thanks to the ongoing collision of the Nazca and South American plates). The entire telescope is designed to swing during an earthquake, and securing the primary mirror prevents it from rattling against the metal tubes that surround it.

There now no one needs to RTFA.

Re:VLEC - Very large egg cartons

[phantomfive]

moderate quakes, of less than 7.75 Richter

Only in Chile would a 7.75 earthquake be considered 'moderate.' Smaller earthquakes have devastated Haiti, Turkey, Taiwan, El Salvador, and parts of the US, India and Pakistan (and pretty much anywhere else such an earthquake has happened).

Re:VLEC - Very large egg cartons

[Alexandra Erenhart]

We get 5s like every 2 months or sometimes more often. We only worry about earthquakes like the one last night, and only very old structures (usually adobe) or very crappy ones (like construction companies that like to "save" a little too much on materials) came down. The rest are holding on and in good shape.

Re:VLEC - Very large egg cartons

[fuzzyfuzzyfungus]

Given that earthquakes do essentially all their damage indirectly, by causing useful infrastructure to stop working and/or crush its occupants to death, the ability of an earthquake to inconvenience a society is overwhelmingly dependent on that society's material culture. Best off are probably places with essentially zero modern development. A population cannot be dependent on infrastructure that it has never had, and lightweight construction out of local plant materials(or fiber reinforced mud, or whatever the local vernacular architecture happens to be) isn't wildly dangerous if it collapses. Next best are likely places like Japan. They are quite wealthy, per capita, and don't have too many serious governance issues, and they have frequent earthquakes, so it is basically just an engineering problem. Have building codes that demand earthquake resistance, follow them.

The further you get from either of these extreme positions, the worse an earthquake is likely to be. If earthquakes are infrequent, it is less likely that building codes will take them into account (or, particularly in places with governance issues) that people will bother with those parts of the building code. If danger isn't seen as immediate, people are less likely to respond to it. If people are poor, but have some access to modern construction techniques, they are likely to get the worst of both worlds. Cheap concrete construction, often done by amateurs, is about the worst possible thing that you could be doing in an earthquake zone; but it is absolutely ubiquitous in zones of more or less modernized poverty. Being modern enough to have a dense population that will start to die like flies when water/sewer/food distribution systems break down is also a bad move; but quite common.

Energy is energy, and powerful earthquakes will always be somewhat risky and(in places with advanced infrastructure) rather costly to clean up; but mass death is almost always a symptom of either tsunami or terrible construction practices.

Re:VLEC - Very large egg cartons

[Neoprofin]

Not to split hairs, but I think it's a bit off base to compare anything earthquake related that has happened in the US to Pakistan or Turkey. The 1999 Izmit earthquake near Istanbul killed 18-40,000 people, the Kush earthquake in Pakistan nearly 80,000.

By comparison the USGS records 37 earthquakes in the last 100 years, most of them in densely populated southern California, the combined death toll isn't over 500. I don't think the term "devastated" applied.

Re:VLEC - Very large egg cartons

[toddestan]

Well, if you extend the 100 year timespan a bit, you can include the 1906 San Francisco quake, which is the worst quake in US history in terms of loss of life and property damage. The fact that the loss of life since then has been so low has a lot to do with the lessons learned from that quake.

Stuttering?

[Tablizer]

I.i.i S.s.s.e.e.e S.aa.aa.aa.ttt.uu.rr.nn!

Re:Better than

[phantomfive]

No, this was a monster 8.8 earthquake, approaching a hundred times bigger than the Loma Prieta earthquake that hit San Francisco in 1989, collapsing a bridge and causing massive damage. This is not an easy thing to protect against: the observatory is lucky to be far away from the epicenter, and would be insane to not prepare for earthquakes in such an earthquake-prone area.

The amazing thing is that so many buildings remained standing with an earthquake that size. Structural engineers are still not entirely sure how to deal with that kind of quake, because they happen so rarely. They did better preparing for quakes than SF did, or probably any county in the US.

Re:Still confused

[MichaelSmith]

Oh okay so the mirror is fixed to the structure of the telescope but the telescope is on an azimuth-altitude mount or similar and it kind of hangs from the mount so it can swing around if it needs to. Makes sense.

Re:Better than

[Chris Burke]

They thought about that, but putting a clamp-and-swing system in place for every person, and for these people to constantly remain where the clamps can grab them in case of an earthquake, turned out to be impractical.

Re:Better than

[ucblockhead]

That same area experienced an ungodly 9.5 earthquake (worst ever recorded) in 1960 so they have both experience and incentive in earthquake safety.

Re:Better than

[jgardia]

sorry, being Chilean, I don't expect more than 1000 deaths at all. We are not the most developed country in the world, but at least we now how to build.

Re:Better than

[HornWumpus]

Richter scale is a useful measure for geologists as it measures the approximate total energy released in the quake on a log scale.

Structural engineers on the other hand measure earthquakes mostly by maximum G load incurred and the type of waves.

Long duration earthquakes (as this one appears to be) are generally less destructive then they would appear based only on their Richter rating.

More data is sure to come regarding the peak intensity of shaking.

Re:Better than

[lathama]

The news being broadcast in the USA show pictures of destruction of a few places, the tsunamis are the big concern as the Chileans watch the news of deaths in Asia... I walked to the office today in Vina and did not see any issues with buildings other than some broken windows... A crack in the cooling system on the Data Center is the biggest damage I have experienced...

Re:Better than

[Natales]

Look, Chile implemented some really good construction codes after the 1985 quake in Santiago, which coupled to the remarkable economic growth and new buildings built after that, has resulted in a highly improved situation, which has been proven today. But that is mostly in Santiago. Look at what's going on in Concepción, Talcahuano and the smaller communities in the South...

The fact that building codes are much better now is NOT an excuse to be arrogant. Even 1,000 deaths is a lot of people. People with families. I'm also a Chilean geek living in Silicon Valley, and I've spent all day using all available technology to connect not only with my family, but to help others connect with their loved ones. Live Chilean Internet TV + Tweeter + Facebook + Google Voice with SMS and my Asterisk-Gizmo SIP link + IM + Skype + probably more that I'm forgetting now.

Instead of betting on the number of deaths and brag about the building codes, get off your ass and start helping in any way you can.

Re:Better than

[ElectricTurtle]

If so, then that god is total dick.