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."

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: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.

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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: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...