Gary Greenberg (gberg) Wed 27 Apr 11 14:14
Your account of strain relief reminds me of what happens at the chiropractor--a good pop seems to relieve some kind of tension. Now, if only we could feel the stress building up in the tectonic plates or whatever. If it were possible to burrow down to where the action of an earthquake is, would we see a pile of rubble where the pop happened? Is it like an explosion deep underground?
Andrew Alden (alden) Wed 27 Apr 11 14:18
Before I go on any longer, I should point out a public talk on earthquake prediction will be given by well-known seismologist Susan Hough tomorrow in Menlo Park, California at the US Geological Survey. If I understand the format correctly, she gives an expert lecture at noon and a nontechnical one in the evening. Both will be streamed live. Details at <http://online.wr.usgs.gov/calendar/>
Andrew Alden (alden) Wed 27 Apr 11 14:47
<23><24>: the 1755 Lisbon quake -- This is one of those "prehistoric" events that we can only study from documents and maybe some ruins. The quake happened at probably the worst time possible -- not rush hour on Friday. No, it was on All Saints Day, 1 November, right after church. To the people of the time, alert for divine signs and in a society based on religiously ordained order, it was a profound shock that I don't think any American can fully appreciate today. The rest of intellectual Europe was thrown into turmoil, and the technocrats of the time were spurred to apply rational inquiry (the word "science" was unknown then) to the event as a natural phenomenon. It's worth noting that England had suffered a large earthquake in 1750, and of course the Mediterranean is rattling all the time. Anyway, modern research points to the plate boundary between Europe and Africa, out in the eastern Atlantic, as the source. Wikipedia has a nice summary at <http://en.wikipedia.org/wiki/1755_Lisbon_earthquake>. The Azores are at the other end of that boundary, a group of volcanic islands. Volcanoes are not strong things, just piles of broken rock glued together with tongues of lava. They erode quickly, and they tend to rot inside and collapse, and magma intrusions can disrupt them from the inside too. Seafloor surveys have found big chunks of broken volcano, clearly fallen off the islands at some point in the deep past. Hawaii is also well known for that. Obviously the splash from something like that would constitute a huge tsunami. The scientists who put together that scenario in the 1990s caused an uproar, naturally, but just as a weak building or a large tree being cut down gives many signs of its impending collapse, surely a volcano will do the same thing. At least, these days the volcano monitoring programs so famously derided by Gov Bobby Jindal rely on such signs when they issue warnings that have saved many lives. So, like the Yellowstone "supervolcano," the Azores will give us centuries of warning.
Mark McDonough (mcdee) Wed 27 Apr 11 14:59
Just as an aside, Jindal is a former Rhodes Scholar, so I can only assume that his statement was pure grandstanding.
Andrew Alden (alden) Wed 27 Apr 11 15:03
<25> David, I don't want to mangle physics I may not be properly understanding, but it's clear in physics as well as intuition that energy wants to channel itself toward the most efficient configuration. Even a jagged fault through rock that has never broken before will work its way, over time and repeated events, toward a smooth plane. That leads to Gary's question, what do faults look like way down there? They're not crisp, thin cracks but wide zones of crushed rock. Near the surface, where rock is most brittle, this layer of fault gouge can be hundreds of meters thick, like at Tejon Pass on the San Andreas fault: <http://geology.about.com/od/geology_ca/ig/saf1857/saf1857i5gouge.htm> Click the next photo for a closeup. Deeper down, where it's hotter and more chemically active, the gouge is readily turned to clay minerals. Bodies of serpentine rock are also very slippery and seem to attract faults. When a drilling project in Parkfield, California succeeded in crossing the San Andreas fault at depth, the cores were displayed at a memorable press conference: <http://geology.about.com/od/seismology/ig/safod/pressconf.htm> My photos of the fault zone follow that picture. Deeper still, the friction of an earthquake can actually melt the rock, leaving a telltale feature called a pseudotachylite. I wrote about them at <http://geology.about.com/od/rocks/a/aa_fractfrict.htm>
Andrew Alden (alden) Wed 27 Apr 11 15:18
Heh -- I just got a note from the US Geological Survey about my email Earthquake Notification Service, which I've had for years. Last month after the Japan quake, I got an alarming number of messages for the aftershocks, something like a hundred of them in just a couple days. The USGS said they've just added "aftershock exclusion" to the system by default. But I'm going to log in and add them back because I keep ferocious tabs on my email inbox. Anyone can sign up for ENS service at <https://sslearthquake.usgs.gov/ens/> and get email for quakes all over the world. Another thing I do routinely, as part of my morning warmup, is visit the USGS page of California and Nevada earthquakes at <http://earthquake.usgs.gov/earthquakes/recenteqscanv/>. The pattern of small events is interesting to watch, and of course anything big (M 4.5 and bigger in the U.S.) I get ENS messages for.
We're carrot people. (unkljohn) Wed 27 Apr 11 15:18
Thanks for this. I find it all fascinating.
Tom Howard (tom) Wed 27 Apr 11 18:54
Thanks for all, and most recently the discussion of Mark's Lisbon question. Also, interested in something Mark, I believe, brought up in the general Japan Fukushima reactor problems discussion: there was a huge tsunami that occurred in the same area 1200 yrs ago; if the reactor's lifespan was calculated to be at least the 40 yrs it's been there; that ended up giving us a 1/30 chance that the plant would be overwhelmed by another tsunami. a. is my math correct b. is this a legitimate way of looking at the risk? Would you move next to something that had a 1/30 chance of killing your newborn?
Mark McDonough (mcdee) Wed 27 Apr 11 21:00
Which actually raises an interesting question for everyone here who lives in earthquake country - how do you think about the risk day to day? I lived in San Francisco for several years in the late 1970s and early 80s after taking a bunch of courses in geology. One of these courses included the showing of a very well-made film about San Francisco with the title "The City That Waits to Die." Even knowing all this, I moved there and enjoyed living in San Francisco.
David Gans (tnf) Wed 27 Apr 11 21:27
As noted earlier, I have lived in California my entire life and I have experienced hundreds of earthquakes including some big ones. I have never sustained one bit of damage - not even books knocked off shelves.
Andrew Alden (alden) Wed 27 Apr 11 21:27
The risk? I dwell every day on the possibility, not the risk. Maybe that's just a good way of living with risk without thinking about it, but to my mind odds are a crapshoot. There is no really sound theory about earthquake recurrence, only odds. In the case of my fault, the Hayward fault, we know from trenching studies that there have been about ten large quakes over the last 2000 years or so; the average interval between the last six is 140 years, and it's been 142-plus years since the last large quake in October 1868. Beyond that is simply unknown, and I strive mightily, as do most seismologists, against the idea of being "overdue" for the next earthquake. One of the hardest scientific ideas for humans to grasp, and one of the latest to enter science and the public domain, is probability and its relation to randomness and order. When you think that modern science began with perfect Euclidean geometry, absolute time and space, the clockwork cosmos of Copernicus and Newton -- that's centuries of bias toward the Cartesian notion that everything can be rationalized and calculated. Earthquakes are very close to random, at least in time. We do have pretty good information on where they occur in space, but anything beyond that -- sizes or dates, for instance -- is simply a blank. We don't have any way of choosing Door Number 1, 2 or 3 through 100. But I'd like to know how others of you go about your lives in earthquake country.
David Gans (tnf) Wed 27 Apr 11 21:42
We have some earthquake prep in ur house, but not much. One cupboard in our kitchen with a latch so we can be annoyed every damn day of our lives rather than have to pick up shards of coffee mug when that day does come.
Dan Flanery (sunspot) Wed 27 Apr 11 21:42
>Which actually raises an interesting question for >everyone here who lives in earthquake country - how >do you think about the risk day to day? I probably think a little about it every day. I was nuts about earthquakes and - to a lesser degree - tsunami when I was a little kid (also, dinosaurs!). They scared the shit out of me, but I found them fascinating. One of my favorite books was one of those little Scholastic books on earthquakes I got at a school book sale. I remember reading that thing in bed many, many times just before dozing off. It was published in the early '70s, when plate tectonics was new, and had a lot of coverage of the big Alaska quake. I remember when we visited a great aunt in Chino in '77 or thereabouts that I was very nervous regarding earthquakes. It's ironic I'd end up living in earthquake country. I guess I confronted my fears. But I'm also fairly well prepared for a quake. I have a large earthquake kit with food and water, a campstove, cookware, rope . . . even an axe. And after watching footage of the folks in New Zealand coping with the aftermath of the Christchurch quake I bought a couple of hardhats, one for home and one for the office. There may be lots of rubble to contend with, and folks who need rescuing.
Dan Flanery (sunspot) Wed 27 Apr 11 21:43
I need to get those latches, though...
Mark McDonough (mcdee) Wed 27 Apr 11 22:16
There is some truth to the "overdue" concept, isn't there? Yes, there's an element of randomness, but quake intervals also reflect plate movement (building up strain) and the strength and "stickiness" of the fault boundary. So sure, if the last n quakes in a particular area have happened on average every 250 years, that doesn't really mean you're 10 years overdue at 260 years - but it definitely means you're pretty unlikely to go 750 years without a quake unless something has changed.
paralyzed by a question like that (debunix) Wed 27 Apr 11 22:30
Re: earthquake preparedness--I'm a native Californian, used to the occasional shake rattle & roll. I do think about earthquakes when I'm setting things up & rearranging and redecorating, and do a few simple things like keeping bookcases slightly tilted towards the wall, and storing some fragile items in cupboards rather than displayed on open shelves. By habit & inclination I always have plenty of food in my pantry, although not all of it is 'ready to eat'--but a little water and fuel and I could feed quite a few people for many days with the bulk grains and beans etc. I've got matches and candles and flashlights, but have never developed a proper emergency kit--I just can't stand the idea of buying gallons and gallons of unneeded water, boxes of batteries, and cans of food that I don't otherwise have any need for, to be wastefully disposed of (once outdated and needing replacement, most places you could otherwise donate such won't accept it) and replaced at regular intervals, and ditto batteries and other things that need to be kept fresh. Instead, I hope a neighbor with a barbecue keeps enough charcoal & bottled water that we can make do together with my hotpot & hibachi and stores of beans and rice. If I'm able, I expect I would be spending most of my time at work at the hospital (I live within walking distance), filling in for some others who might not be able to get there, depending on the degree of infrastructure damage. Or perhaps I'll just get thoroughly squished by one of my unsecured bookcases, and then it won't matter whether I was otherwise prepared or not!
Mark McDonough (mcdee) Wed 27 Apr 11 22:44
While I'm not expecting a 9.0 in Northern Virginia, I'm like you - I've got a ton of food in the pantry. My Mormon neighbors saw it once and said I had way more than them (which is a little worrisome).
spinning around like an errant, tuxedoed rinse cycle (thelobster) Wed 27 Apr 11 23:17
>a. is my math correct >b. is this a legitimate way of looking at the risk? Would you move next to something that had a 1/30 chance of killing your newborn? I don't want to derail yet another earthquake discussion into a debate about nuclear energy, but I'll just say that I don't think that your math is correct. For there to be one in thirty odds, you'd have to assume that 100% of the newborn babies living in the Fukushima exclusion zone were killed. As far as I know the actual percentage is rather close to zero, rather than 100%.
Ed Ward (captward) Thu 28 Apr 11 02:49
Thinking of Lisbon makes me wonder about the Western Mediterranean, where I am (Montpellier). I don't think I've ever heard of an earthquake around here, even historically, and when a guy I met told me the city was built on an extinct volcano, I did some googling and discovered that there is an ancient chain of dead volcanoes rising out of the sea at Agde, about 50 miles west on the coast, but nothing around here. Hell, we're all limestone, so we *couldn't* be volcanic, right? Makes me wonder, though: are there any 100% non-quake zones anywhere on the planet?
Tom Howard (tom) Thu 28 Apr 11 07:15
<thelobster>, thanks for mentioning my question. There are so many things wrong with what I was posing, I scarcely got around to posting. I was hoping <mcdee> might've mentioned, if it had been him elsewhere, what he was talking about with the 1200 yr recurrence. Anyway, I'm thinking it wasn't so much my math as my postulation. Not that your newborn baby would die, but that the people would allow a plant like that in that area. Ever. And, so, to bring it to the earthquake, why would you subject someone you are responsible for to that risk. The quake will happen, the tsunami will happen, and a 30km exclusion zone will happen. Would you bring your baby to that area? Personally, I am somewhat like <debunix>. Yes, all those things might happen, but I'm not responsible for any children ("children" is just an egregious example), and I'd make do. Living here inside the DC beltway, moved here while the Cold War was going on (remember *that* Ground Zero?), thru our current dirty bomb scenarios, and I'm figuring no matter how bad it might get, I would be better off than others and my job would be to assist.
Mark McDonough (mcdee) Thu 28 Apr 11 07:41
I have some older relatives who live in a fire-prone area. Their house is completely surrounded by thick brush. It's a beautiful area, and it's a beautiful setting for their house. I asked them once if they were worried about fire. They just said they'd get the hell out, let the house burn, and buy an RV. Human decisions about risk are odd. If they were more rational, why would anyone live in, say, Los Angeles, which is subject to fire, flood, and earthquake? Or for that matter in DC, a prime terrorist target. Or build houses on the Atlantic ocean front?
paralyzed by a question like that (debunix) Thu 28 Apr 11 07:56
Or any place prone to tornadoes, which covers nearly everyplace that isn't at risk for wildfires, floods, earthquakes, hurricanes, or volcanoes.... I remember being just a little upset one day, shortly before my departure from California to St Louis, by a map of tornado activity that clearly included St Louis as one of the higher-risk parts of the midwest. In the time I was there, there were of course tornadoes around the area, but the city itself mostly was spared (although this year one hit the airport rather impressively). But I could rationalize the net risk as lower than earthquake country because tornadoes are so localized in their most severe effects. The risk one is going to get *you* is pretty low even in tornado alley. The risk you're going to be affected by a big earthquake nearby is bigger, because their impact is more broadly devastating, but it's more localized in time than in place, so it all balances out. Or something like that was how I rationalized it to myself when I moved back to California.
Ted Newcomb (tcn) Thu 28 Apr 11 08:44
http://www.grist.org/article/2011-01-19-california-superstorms-could-make-quak es-look-tame-and-brisbane- What do you think about these superstorms NOAA is predicting, as well as the solar storms I keep reading about that might electromagnetically wipe out our satellite communication network??? Is this sci-fi run wild or potentially true in our near-future? Are these earthquakes part of some synergistic weather planetary cyclical pattern???
Peter Meuleners (pjm) Thu 28 Apr 11 08:45
I've lived in the greater East Bay my entire life, felt dozens of quakes, including Loma Prieta, and never think about them unless they come up in conversation or one happens. They're just a part of life. If they do no damage I actually enjoy them. They connect me to the planet I walk on in a very direct manner.
Andrew Alden (alden) Thu 28 Apr 11 10:02
Now that's a real California attitude! Philip Fradkin has argued, and I think I agree, that earthquakes have always shaped the Californian character. The very first expedition to California, in 1769, walked right into a large Southern California earthquake. We've always had this charming ability to roll with the punches. Seeking stability in a roiling world is a Zen kinda thing -- and hey, Zen is from Japan.
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