posted
That does not obviate the possibility of consequent Earthquakes. I think Jux already knew the crust would resettle on the mantle with a weight distribution- the question is whether the redistribution of weight can trigger quakes.
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posted
Poisson distributions. The number of high-magnitude earthquakes per decade is sufficiently low that the variance is very high compared to the value. (Even more so when you consider the number that hit in populated regions.) Compare the classic V1-impacts-in-London thing.
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quote:Originally posted by Orincoro: That does not obviate the possibility of consequent Earthquakes. I think Jux already knew the crust would resettle on the mantle with a weight distribution- the question is whether the redistribution of weight can trigger quakes.
Basically. I'm always happy to learn a new word though. Posts: 2907 | Registered: Nov 2005
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quote:(CNN) -- The massive earthquake that struck Chile on Saturday may have shifted the Earth's axis and created shorter days, scientists at NASA say.
The change is negligible, but permanent: Each day should be 1.26 microseconds shorter, according to preliminary calculations. A microsecond is one-millionth of a second.
A large quake shifts massive amounts of rock and alters the distribution of mass on the planet.
I'm assuming that this isn't actually that weird for an quake of that magnitude, and that this sort of thing has happened before, we just haven't been able to measure it until relatively recently.
But between this and Haiti (and on a smaller but more local scale, the huge snowstorm that caused a power outage for 90,000+ people in my area), I feel like Nature is giving us a not-so-gentle reminder that she is orders of magnitude more badass than we are.
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quote:Should tickle the Obama administration if the day is shorter they will have their tax people in our pockets quicker and they can figure ways to spend more money.
quote:Maybe if the day is shorter and it screws up the electronics there will be less junk stuck in peoples ears and eyes so they can see the road better.The scariest thing in the world is to see someone looking straight at you at an intersection and have a cell phone stuck in their ear and no not what the devil they are going to do next.
quote:It just means that my credit card bills will arrive earlier.
quote:Originally posted by Raymond Arnold: I'm assuming that this isn't actually that weird for an quake of that magnitude, and that this sort of thing has happened before, we just haven't been able to measure it until relatively recently.
This is not a measurement based on observation, it's a projection- meaning that it assumes this happens with all similar quakes. Don't worry though- the Earth's rotation is augmented and retarded constantly by seismic events and extraterrestrial forces- particularly the other planets. The variations are routinely larger than this one, and they are constant.
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I was in Taiwan during a slight tremor. For some reason because I was at the top of a tall building it felt like the roof was swaying back and forth. It was definitely an adrenaline rush.
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posted
I've been on the ground in an earthquake and that's what it felt like. I can imagine it being a bit more disconcerting on a roof.
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Okay, not a very big one, not a big deal. All these recent earthquakes are a pretty freaky coincidence. I was listening to a report on NPR about how one earthquake can't possibly transfer enough energy across the globe to create an earthquake across the planet, but I'm starting to wonder if there's a single point causing them all, rather than them affecting each other. But then, what do I know about seismology? Almost nothing.
What I think is most likely, is that we've been hit with a coincidental series of large earthquakes, and the hysteria has caused the media to overhype several smaller quakes that normally wouldn't receive any or nearly as much coverage as they are. So it feels like we're surrounded by quakes, building up to the conclusion of a made for TV SyFy movie.
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quote:What I think is most likely, is that we've been hit with a coincidental series of large earthquakes, and the hysteria has caused the media to overhype several smaller quakes that normally wouldn't receive any or nearly as much coverage as they are. So it feels like we're surrounded by quakes, building up to the conclusion of a made for TV SyFy movie.
posted
Several years ago I subscribed to the USGS earthquake alert email notification system, and set my threshold such that I would get notified anytime there was an earthquake of greater than 5.0 magnitude anywhere in the world. I haven't seen an increase in the number of earthquakes lately.
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quote: So it feels like we're surrounded by quakes, building up to the conclusion of a made for TV SyFy movie.
I hope not...those movies are completely AWFUL! SyFy can make a great series, but terrible terrible movies
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posted
The entire city of Concepcion was moved ~10feet (303.9centimetres) to the west by the earthquake. And SouthAmerica was expanded by ~9feet11inches (3metres) between Concepcion,Chile and BuenasAires,Argentina.
Lawyers are gonna have tons of fun defining the new property lines.
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quote:Roads were torn up, buildings cracked and electricity posts toppled on Monday after a 7.2 magnitude earthquake shook cities in northern Mexico and Southern California, but few casualties were reported.
Mexican civil protection officials said at least one man died in a collapsed house and about 100 more were injured in Sunday's quake.
posted
Well, it's not really related to the Chile earthquake, but it suggests bad news for California proper might be coming up.
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quote:A major earthquake of 7.7 magnitude struck off the coast of Aceh on the Indonesian island of Sumatra on Wednesday, but there were no immediate reports of casualties.
quote:Originally posted by Jhai: Well, it's not really related to the Chile earthquake, but it suggests bad news for California proper might be coming up.
Not really. The Big One is probably happening some time in the next 30 years.
posted
Aren't you guys overdue? I can't remember the average length for when big ones hit California, but the last one was what, a hundred years ago? And they come every hundred or so years don't they?
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posted
Assessing seismic risk is a rather controversial (within the profession) and in-exact thing. We really can't measure very much that directly relates to earthquake activity and are just making guesses. The amount of differential motion between plates is something (though we haven't been able to do that very accurately until pretty recently) but most of the maps are actually based almost entirely on past history of earthquakes. If you cared enough to look (and I don’t know why you would) you’d see a change in the maps every time there’s an earthquake, and then general changes every so often to account for all the little ones (I can’t remember how often they do these). There’s a relatively high seismic rating around New Madrid (a bit south of St. Louis) despite the fact that we can’t really “see” any fault lines there. Recently there have only been small earthquakes in the area, but in the early 1800s there was a very, very large quake and so the maps show a high seismic zone. It’s a problem: some faults generate large earthquakes infrequently where others generate small earthquakes constantly (so to speak), and then some do both. There’s really no way to tell what any particular fault is other than looking at the historical record and our data just doesn’t go far enough back to be sure of anything (particularly in the US). If the New Madrid earthquake had happened 50 years, or especially 100 years earlier all our seismic maps would be different, but obviously nothing would be different about the actual danger posed by the fault.
The links Rivka posted are very good descriptions, but California is actually an aberration from the remainder of the country. Basically they both set the standard, and then grandfathered in the parts that didn’t make the national standard. They’ve been dealing with the problem longer than anyone else so they rely a lot on past experience. The way the national earthquake codes work is based on the ‘Maximum Considered Earthquake’, or MCE which is about once every 1500 years. We have about 100 years of reliable data, and even that isn’t very complete. Even California’s code is really based on the MCE, but with grandfathered in clauses referring to this 50 year exceedence stuff (the technical specs come out literally identical, they just get to use different language). Trying to predict the largest ground motions possible for 1500 years (when these things are highly variable as is, it’s not like you’d actually be sure you saw it every 1500 years) with 100 years of data is kind of a farce. But you’ve got to base it one something and this is the best we’ve got.
posted
Thanks for the links rivka, and the explanation, Hobbes. That was very informative (and interesting!). I wonder if I was confusing quake predictions with eruption predictions for volcanoes. But now I'm not even sure about that. I don't suppose we have a resident vulcanologist in addition to seismologist?
Either way I'm happy to know more today than I did yesterday.
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quote:Chinese media say at least 67 people have died and others are trapped under rubble in Qinghai province after an earthquake said to be magnitude 6.9.
The quake struck at 0749 (2349 GMT) 380km (240 miles) south-south-east of the city of Golmud, at a depth of 10km, according to US Geological Survey data.
posted
Does Qinghai count as being on the Ring of Fire?
Anyways, news update:
quote:A series of deadly earthquakes – the biggest registering 6.9 – ripped through a remote region in southwestern China Wednesday killing hundreds and injuring thousands.
State media reported at least 400 had died and between 8,000 and 10,000 were injured as the Chinese government mobilized rescue efforts to reach to the remote area of Yushu county in Qinghai province.
quote:Originally posted by Mucus: Does Qinghai count as being on the Ring of Fire?
Close, no?
And updated reports I'm seeing say it was actually 7.1. Edit: Ah, that's what the Chinese government is saying; the USGS says 6.9.
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posted
I don't actually know what close is in this context. But totally eye-balling it, Qinghai is as close the Ring of Fire here as is Manitoba or whatever US state is directly south of Manitoba.
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posted
It's not fair. Why do they make women cover themselves up to protect young men, but I'm still forced to live in a world with a buff and shirtless Hugh Jackman?
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posted
Seems like. Really felt those p-waves, though. (I think those are the ones that can trigger nausea, no?)
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It's 200 miles further out than the one that killed so many in Banda Aceh. Looks like about an hour ago the tsunami warning went out, so people are headed for the hills. Some places are getting predictions of waves several meters high. It's not as powerful as the Banda Aceh quake from years ago or the Japan quake from last year, but it's still a biggie.
Update: Despite the tsunami warning, a rep from the US Survey says a tsunami is unlikely given the type of earthquake.
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