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

[bar-agent]

There now no one needs to RTFA.

I'm glad I did though. That underground oasis they have in the slideshow is pretty.

Re:VLEC - Very large egg cartons

[jgardia]

Well, today's one was 8.8. anything less than 5 is not considered an earthquake at all.

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

[jonadab]

> Only in Chile would a 7.75 earthquake be considered 'moderate.'

I think there are a couple of other places too, most of which are on one edge or another of the Pacific. But yeah, Chile is one of the major earthquake zones.

On the other end of the spectrum you have places like Ohio. Anything over 3.0 dominates the news for days. I still remember where I was when we had a 4.something in the mid eighties, which a few people even claimed they *felt*. People didn't stop talking about that one for weeks.

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

[Dalroth]

"Claimed?"

Dude, our lockers started rattling! My 4th grade teacher, who had just moved from California FREAKED. I guess she though she finally escaped them. The rest of us were like "wtf was that?"

We definitely felt it, no doubt about it.

Brooklyn, OH represent!

Re:VLEC - Very large egg cartons

[jonadab]

You must have been significantly closer to the epicenter. Where I was (attending school in Massillon), only a percentage of the people who were seated indoors claimed to have felt it. Nobody who was standing noticed anything. My class was out on the playground at the time, so we only heard about it after we came in from recess. We were pretty disappointed that we'd missed it, because an earthquake large enough to feel is pretty much a once-in-a-lifetime proposition in Ohio.

Re:VLEC - Very large egg cartons

[marcosdumay]

When there is something* bigger than 4.4 at any point of Brazil, all the press freaks about it for at least a week, nationwide.

*Normaly due to some mining or construction problem.

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.

Re:VLEC - Very large egg cartons

[jonadab]

> When there is something* bigger than 4.4 at any point
> of Brazil, all the press freaks about it for at least
> a week, nationwide.

Makes sense. Brasil is on the Atlantic side, with the western border falling a few hundred miles shy of the quake zones. So, its quake profile would be pretty similar to the eastern three quarters of the US.

The difference up here is that California and Alaska, on the Pacific side, are part of the same country. Consequently, our national news doesn't freak out over a 4.5, because they have them all the time over there. Only the local and regional news go nuts, and only if it happens in a seismically tame part of the country (i.e., not on the west coast). Nobody cares if there's a 4.5 in southern California, just like the news services in Brazil probably don't freak out when there's a 5.0 in western Peru.

Re:VLEC - Very large egg cartons

[marcosdumay]

It is easy to understand. Yet, it doesn't stop to be amusing seeing television news make a week long fuss about some house 3000km away that got scratches because of a tremor. I'd expect news to ignore 5.0 quakes at Peru. I'd also expect them to ignore local ones.

Better than

[Threni]

they protect the people who lives there, one assumes.

Re:Better than

[John Hasler]

Why do you assume that the people who live at the European Southern Observatory are not well protected?

Re:Better than

[MichaelSmith]

I think the GP means the telescopes get more protection than the people of Chile. Expressing it differently: its too early to be discussing the telescopes. For all we know there could be 10000 people dead, given that communications are spotty.

Re:Better than

[MichaelSmith]

Actually, reports seem to indicate that they did fairly well.

Yeah I read a long time ago that they have an emergency warning system tied to telephones so they can broadcast messages to people quickly through the phone system. They seem quite organised.

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:Better than

[MichaelSmith]

The amazing thing is that so many buildings remained standing with an earthquake that size.

Maybe because they have so many big quakes these are the few buildings which were built strong enough not to fall down. More natural selection rather than intelligent design. We just need to find a way for buildings to breed...

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

[MichaelSmith]

Thats good to hear. Thanks.

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

[MichaelSmith]

I think the tsunami was 20cm in New Zealand, 10cm on an island east of Tasmania and maybe a few cm on the east coast of the Australian mainland. So over here its not bad at all.

I wondered if the comparatively big wave on the coast of Chile was caused by a landslip under water.

Because of the distances involved there seems to have been plenty of time to send the word around to get people clear of the water. Beaches were closed in suburban Sydney because its the kind of place where people would sit in the water to feel the tsunami for themselves.

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]

Japan has one of the highest population densities in the world, 873+ people per square mile (and a whole lot higher in Kobe specifically). Chile has one of the lowest population densities in the world, 58+ people per square mile. That goes a long way in mitigating casualties.

Re:Better than

[ElectricTurtle]

If so, then that god is total dick.

Re:Better than

[sictransitgloriacfa]

Well, if you get a lot of earthquakes, you don't end up with many buildings that can't survive them, do you. One way or another.

Re:Better than

[Neoprofin]

Not just "that area", the tsunami from the 1960 quake killed 61 people in Hawaii and there were 10m tall waves as far away as the Philippines and Japan. The really scary thing is just how quickly the waves can spread, only something like 25 hours to cross the ocean.

Re:Better than

[Schmorgluck]

This, plus Kobe is a special case, the focus of the quake being only 16 km deep, and its epicenter only 20 km away from the city. Taking into account the approximations of the above figures, that makes an hypotenuse of mostly 26 km, which is pretty close.

Plus, I remember hearing that some lens effect came into play, due to the density configuration of the underground, but I'm presently unable to find any reference to it, so it may be a false memory.

Re:Better than

[rtbyte]

It may be that I have a false memory too (ugh), but I remember from some (discovery ?) movie that there was some other effect (lens or not) that came into play in Kobe and amplified the quake.

Re:Better than

[CGordy]

Well, if you get a lot of earthquakes, you don't end up with many buildings that can't survive them, do you. One way or another.

There's two theories as to why:

• The fittest buildings survived.
• The buildings still standing were more intelligently designed.

Re:Better than

[RockDoctor]

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

The Richter Scale is a scale that was designed around a half-century ago around the readings of a particular model of seismograph deployed in southern California, and with various other technical details to do with distance to hypocentre etc which were also specific to it's origin. Since the 1970s (possibly the 1960s - IANA-historian of seismology), the preferred measure for comparison of earthquakes has been the moment-magnitude parameter, which (not accidentally) has approximately similar numerical values for quakes that overlapped. (Obviously the original models of seismograph are long since defunct, so direct comparison is probably not possible, and not likely to be helpful.)
All of these scales are, as you say, logarithmic.
If you see a professional seismologist on the TV, you'll almost certainly not see the "level-setting" footage and the other technical necessities of filming ; that stuff on the cutting-room floor will be the bit where the seismologist bemoan that the journalists really should stop talking about the Richter Scale, because it's as relevant these days as the Roman mille. If you do see a professional seismologist referring to the Richter Scale outside wordings like "approximately equivalent to X on the Richter Scale", then they've probably just given up on educating the bloody journalists, let alone the trampling masses.

Re:Better than

[soulprivate]

In fact, Chile and Japan have been exchanging engineering methodologies to build anti seismic buildings since the 60's. Go Chile, we will rise!

Stuttering?

[Tablizer]

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

Still confused

[MichaelSmith]

secure it to the telescope’s support structure ... is designed to swing during an earthquake

So is the mirror free to move, or is it locked to the structure? The first would make sense for a small quake. The latter might be better in a big quake.

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.

Priceless?

[Wowsers]

I read the summary (and the articles).

A human life is priceless (to someone), an object that can be knocked down and built again is not priceless.

Re:Oh really

[NeMon'ess]

You missed the parenthesis. The OP is correct. A human life is priceless to someone, not to everyone.

Re:Oh really

[The End Of Days]

Who cares about parentheses? SmallFurryCreature incited the argument and supplied both sides, it's not like there was any logical foundation for the post in the first place.

Re:Priceless?

[tomhudson]

If it is too expensive to build again, or if it would be replaced with something else, it may in fact be "priceless" in the sense that money will not ever be allocated to replace it.

A good example is the current fleet of space shuttles. They are priceless in this sense. Once they are gone, they are gone for good.

A correction

[syousef]

7.75 is not considered moderate. 7.74 is. ;-)

Re:A correction

[phantomfive]

*slap*

Re:Priceless?

[Rakshasa Taisab]

We have 6-7 billion people and constantly make more than we can handle. While there's probably only a handful of those rather expensive mirrors.

Easy enough

[Bloom Berg]

I'm pretty sure they use this thing called "insurance".

Re:Fortunately

[mangu]

Fortunately, those telescopes are to the north of the epicentre in Chile and not to the east.

Nothing is "to the east" of anywhere in Chile. That would be in Argentina.

Re:Priceless?

[PatrickThomson]

What about the 100 men that gave a year of life to the project? Is that worthless?

ESO press release

[RockDoctor]

"A magnitude 8.8 earthquake struck central Chile at 03:34 local time (07:34 CET) on Saturday 27 February 2010. The epicentre was 115 km north-northeast of the city of Concepción and 325 km south-west of the capital Santiago. The earthquake has caused significant casualties and damage in the country.

ESO expresses its deepest condolences to the families of the victims, and its sympathy and support for all those affected by the earthquake.

No casualties among ESO staff have been reported. At present, power cuts and network interruptions mean that communication may be limited. Disruption to staff travel plans within, to, and from Chile should be expected. We urge Visiting Astronomers with observations planned at ESO observatories to put their trips to Chile on hold until further notice. International flights to and from Santiago International Airport are currently either cancelled or diverted. Information about observing programmes will be provided at a later date.

Despite being the 7th strongest earthquake ever recorded worldwide, the ESO observatory sites did not suffer any damage, partly as they are engineered to withstand seismic activity and partly due to their distances from the epicentre. At La Silla, a power cut caused observations to stop during the night. Paranal Observatory, the APEX telescope and the ALMA Operations Support Facility and Array Operations Site were unaffected."

A 7.8 quake struck Antofagasta (120km north of the telescope site) in 1995 (http://www.eso.org/public/news/eso9517/).

Various other quakes in the area : http://www.eso.org/gen-fac/pubs/astclim/earthquake/his-paranal-58.html (Historic times to 2000.)

http://earthquake.usgs.gov/earthquakes/eqarchives/epic/epic_circ.php allows you to get at historical quakes map up to 1994 ; 1973 to present and various other formats ; there has been plenty of data for planning quake likelihoods and the engineering responses that would be required.

Blame Peru!

[Mal-2]

It's all because the Peruvians chase their earthquakes away! Where are they going to go? Chile, of course! Superstition seems to be protecting Peru, but at what cost to their neighbors?

Mal-2

just my 10 cents

[soulprivate]

I am chilean, and just two weeks ago, I visited the Tololo Observatory during my vacations. They explained exactly this subject : the telescope itself is embedded on solid rock (not just a concrete or cement foundation). This rock base is surrounded by the typical dome or cupola. Therefore, the telescope and the cupola building are *separate* and almost independent structures. Go Chile, we will rise!

Re:Fortunately

[soulprivate]

Just this time, the earthquake epicentre was located in the southern part of Chile. The region were the telescopes are located (north of Chile) have been the epicentre of some pretty nasty quakes these past 20 years. Go Chile, we will rise!