Wikipedia:Reference desk/Archives/Science/2012 August 3

= August 3 =

Magnitude 10 earthquake by combination of faults
I heard on a Discovery Channel program that a magnitude 10 earthquake could occur if the Cascadia subduction zone, the San Andreas Fault, and the Aleutian Trench all simultaneously ruptured. Is this possible? If so, how likely?--Jasper Deng (talk) 04:08, 3 August 2012 (UTC)
 * It's mentioned in the Cascadia article you linked to. 10-14% for magnitude 9 or higher in the next 50 years.  Hot Stop   04:14, 3 August 2012 (UTC)
 * As likely as anything else, which means not likely at all. No earthquake in recorded history has been measured or estimated to have a magnitude greater than 10.  9.5 is the highest I can find at either Lists of earthquakes or Historical earthquakes.  Sadly, the Discovery Channel (and other supposedly educational channels like the History Channel and TLC) have gone down the drain over the past decade or so.  When they do run a "science" show, which is rare, they tend towards the sensationalistic, like impending asteroid impacts or supervolcanos, or stuff like that.  I suppose this is what happens when geologists get really drunk at parties.  Could it happen?  I suppose.  Could it happen this week?  I wouldn't hold your breath... -- Jayron  32  04:14, 3 August 2012 (UTC)
 * Such a quake could possibly be a once-in-ten-milleniums in frequency/probability; I don't hold my breath for any megathrust earthquakes anyway.
 * However, it seems logical. If the subduction zones could each generate 9.5 earthquakes, and the San Andreas Fault a 9.1, then this could produce something like 9.8. If it so happened that another adjacent subduction zone like the one off eastern Russia also joined in, this would easily break 10. The chances of this is extremely unlikely, but not impossible.--Jasper Deng (talk) 04:19, 3 August 2012 (UTC)
 * Basic answer: nobody knows. The general opinion was that the Japanese tsunami quake was extremely unlikely -- until it happened.  The dynamics of large earthquakes are still quite poorly understood, and we only have about 100-150 years of good worldwide data on their frequency, so events that occur less often than that could easily be misunderestimated (as GWB might have put it.) Looie496 (talk) 04:27, 3 August 2012 (UTC)
 * General opinion was spot on. The Japanese tsunami quake was extremely unlikely.  Just because it's actually happened, the chances of it recurring haven't suddenly increased (aftershocks from the original quake aside). --  ♬  Jack of Oz  ♬  [your turn]  11:36, 3 August 2012 (UTC)
 * Indeed. It is a common misconception that unlikely things happening is evidence that they weren't unlikely after all. You can't draw conclusions from a single data point like that. --Tango (talk) 11:42, 3 August 2012 (UTC)
 * But we have had quite a few earthquakes of magnitude larger than 9 in the last 100 years. Count Iblis (talk) 15:42, 3 August 2012 (UTC)
 * I've been following the literature on this, and it's pretty clear that many geologists have seen the Japanese quake as a wake-up call indicating that many probability estimates need revision. This overview from Science (available online here at the moment) may be helpful. Looie496 (talk) 16:59, 3 August 2012 (UTC)
 * The problem comes with earthquakes with a long recurrence interval, like the Japanese earthquake and the 2004 Indian Ocean earthquake. We do have some idea about the biggest sections of subduction zones that are likely to rupture, which is about 1600 km as I recall, which is the length that ruptured in the 2004 earthquake. Magnitude is just the logarithm of the product of rupture surface area and displacement, so if we know the biggest area and the biggest displacement, we can work out the biggest magnitude possible. Using data from many large earthquakes it is possible to say that a M 10 earthquake would require a rupture of 1 million square kilometres . The width is relatively fixed depending on the dip of the megathrust and the depth of the top and base of the seismically coupled zone, with a likely maximum of 150 km. However, if we take 200 km, we need a fault length of 5000 km, something like the whole Peru-Chile plate boundary rupturing at once, for which there is no evidence at all. Large earthquakes are often made up of sub-events and they may change in type. The 2002 Denali earthquake started on a small thrust fault, before switching to the strike-slip Denali fault and then splitting off that onto the Totschunda fault, yet another strike-slip fault, so it can happen. Note however, that all these faults physically intersect each other, which the Aleutian Trench and the San Andreas Fault do not (unless you throw in the Queen Charlotte Fault as well). Also, all your separate faults have to be in the same part of their seismic cycle and be close to rupture, which becomes increasingly unlikely as more fault segments are involved. Mikenorton (talk) 22:18, 3 August 2012 (UTC)

Deicing equipment / heaters
Is there any disadvantage to running deicing heaters, whether it's the pitot tube or the other deicers, even if it's not needed? I'm talking about onboard systems too, not deicing on the ground. Shadowjams (talk) 06:06, 3 August 2012 (UTC)


 * 1) I imagine it lowers fuel efficiency somewhat, depending on how they generate the electricity to run them.


 * 2) Running that much electricity through wires has to increase the risk of fire, explosion, and electrocution, if the wires are damaged, but this risk should be minimal in a properly maintained airplane.


 * 3) Running them on a hot day while sitting on the ground might actually cause overheating damage. StuRat (talk) 06:13, 3 August 2012 (UTC)


 * Anybody with cites or definitive knowledge have any ideas? Shadowjams (talk) 06:38, 3 August 2012 (UTC)


 * I'm about to board an international flight, and I'm seated in the first row. I'll see if I can quickly ask the pilot :) 101.172.127.242 (talk) 09:27, 3 August 2012 (UTC)


 * OK, the pilot was happy to answer my questions and took about 15 minutes to talk to me about various things. He said that the Airbus A-320 we were flying in was fitted with a deicing unit for the engines, a deicing using for the leading edge of the wing called "wing air" and small electric heating elements on the pitot tubes. The wing air and engine deicing work by taking a bleed of hot pressurised air from the turbines and directing it to the wing surface or the part of the engine that needs heating. Both of these lead to a performance penalty because they take pressure away from the turbines. The engine deicers are disabled by interlocks when not in the air and the wing air causes an extra take off distance equivalent to about 700kg of extra weight if it's activated on the ground. The power used to deice the pitot tubes is negligible, and that unit is activated automatically during the necessary parts of the flight envelope. 112.215.36.173 (talk) 14:06, 3 August 2012 (UTC)


 * I'm guessing this wasn't in the US, where knocking on the cabin door might get you tackled and arrested by a TSA agent. StuRat (talk) 23:19, 3 August 2012 (UTC)
 * I didn't know the TSA agents actually get on the plane and fly with the passengers. I actually avoided the awkward scenario of knocking on the door by stopping the pilot as he came out to use the restroom. He was very friendly...to the point it was actually hard to end the conversation and get rid of him once I had my answer. He even invited me to come up to the cockpit to see what the indicators look like when the deicers are running, etc. I've flown this route every other week for over a year now, so the cabin staff remember me and are quite friendly, though I obviously havn't spoken to the staff on the flight deck much before. As you can see from the location of my IPs (origin and destination) this wasn't in the USA. 112.215.36.184 (talk) 03:43, 5 August 2012 (UTC)
 * Wow, cool. Thank you! I didn't know pilots actually took time to talk to passengers anymore! Shadowjams (talk) 22:57, 3 August 2012 (UTC)


 * Can we mark this Q resolved ? StuRat (talk) 23:22, 3 August 2012 (UTC)

Ask for help to identify the fungus.
See the link attachment for the Image. Thanks. SYSS Mouse (talk) 15:35, 3 August 2012 (UTC)


 * Location please? Likely to be the young fruiting bodies of any of the bright yellow species of shelf fungi under the genus Laetiporus. If from N. America, likely to be Laetiporus sulphureus.-- O BSIDIAN  †  S OUL  15:55, 3 August 2012 (UTC)


 * Oh dear. I think I saw Steve eat that once. (It goes without saying, but don't eat it.) BigNate37(T) 16:01, 3 August 2012 (UTC)


 * It was not specified. It is from a forum post (The forum is in Chinese thus not linked) but the user who posted it is from Eastern Canada. EDIT: Also, the same fugus one week later.  SYSS Mouse (talk) 16:35, 3 August 2012 (UTC)


 * Definitely Laetiporus then. They're quite distinctive. See this guide. That said, again, don't eat it! :P We're not exactly mushroom experts here, heh.-- O BSIDIAN  †  S OUL  17:25, 3 August 2012 (UTC)


 * Thank You. SYSS Mouse (talk) 03:51, 4 August 2012 (UTC)

Nutrition in Human Breast Milk
I'll freely admit that this question is purely inspired by the Song of Ice and Fire series--

A character in said series is about 8 years old and still subsists primarily on his mother's milk. I'm just wondering if the nutritional needs of a human beyond baby-hood (wherever one draws that line, 8 years old is clearly not a baby) can be met purely through breastmilk. Protein/fat I can see--but does the milk contain enough of the vitamins and minerals?

Puh-lease do not respond with "it's just a book" I'm not asking about the book, that's merely the impetus for the question.199.94.68.91 (talk) 18:46, 3 August 2012 (UTC)


 * Doing a Google search for the phrase "nutrition data human breast milk" turned up this page as the second result (after the Wikipedia article on human breast milk). That page contains all of the data on the nutrient content (including micronutrients such as vitamins and minerals).  Finding the recommended daily intake for these nutrients for an 8 year old should also be easy to find.  By cross referencing those two data sets, you can see where breast milk is both adequate and inadequate for nutritional needs.  -- Jayron  32  19:00, 3 August 2012 (UTC)


 * I asked a question a long time back about how babies can get complete nutrition from milk, which seems to be deficient in several key nutrients. The answer, as I recall, is that babies are born with with excesses of those nutrients, and they switch to solid foods before they run out of this stockpile.  In your case, you said "primarily", so the supplemental foods they get might supply the missing nutrients.  If, however, a child was fed nothing but milk (human or otherwise) for 8 years, then I'd expect severe malnutrition. StuRat (talk) 23:15, 3 August 2012 (UTC)


 * Add to that the fact that the majority of humans become lactose intolerant at around 2 to 7 years of age. They will have limited to no nutritional benefits from drinking milk after that. Though the very recent evolution and growing dominance of lactase persistence is circumventing this somewhat.-- O BSIDIAN  †  S OUL  03:26, 4 August 2012 (UTC)
 * It's very recent by evolutionary standards - it's still about 10,000 years ago. I'm not sure what the overall prevalence of lactase persistence is, but in people of European descent (which I think best describes the character in question, although I haven't actually read the book) it is by far the majority as the article you linked to says. --Tango (talk) 18:04, 4 August 2012 (UTC)
 * Haven't read the book nor follow the series either. :P So I was assuming the OP meant all humans. -- O BSIDIAN  †  S OUL  00:55, 5 August 2012 (UTC)

Is there some reason why there is no link here to human breast milk? Or is the OR of various posters supposed to be more relevant on the wikipedia reference desk? μηδείς (talk) 22:16, 4 August 2012 (UTC)
 * Because it doesn't contain the answer?-- O BSIDIAN  †  S OUL  00:55, 5 August 2012 (UTC)

Filial Imprinting
Hello. Is filial imprinting related in any way, shape, or form to evolution? If so, how? Thanks in advance. --Mayfare (talk) 19:25, 3 August 2012 (UTC)
 * Anything that influences survival is related to evolution. Since filial imprinting enhances the survival of the young (by helping them stay protected), it is related to evolution.  Of course "related to evolution" is an extremely vague term -- if you have something more specific in mind, please clarify. Looie496 (talk) 20:55, 3 August 2012 (UTC)
 * Filial imprinting can augment and override evolutionary instincts by allowing offspring to mimic learned behaviors appropriate for specific environmental conditions. 207.224.43.139 (talk) 05:56, 4 August 2012 (UTC)
 * It is related to evolution in that it is a characteristic that evolved. Was there another relationship you were thinking of? --Tango (talk) 11:17, 5 August 2012 (UTC)

I was thinking along the lines of ethology and maybe natural selection. --Mayfare (talk) 16:11, 6 August 2012 (UTC)

HF solid-liquid transition: densities
Does anyone know if solid HF expands (like regular substances do) or contracts (like does very similar water, both have hydrogen bonds and so) upon melting? Has this been measured (I've done a search, returns nothing)? Are there values?--R8R Gtrs (talk) 19:33, 3 August 2012 (UTC)
 * What search returns nothing? Googling the obvious keywords suggests this depends on pressure because of different possible crystal structures. 207.224.43.139 (talk) 05:55, 4 August 2012 (UTC)