Zipingpu Dam May Have Triggered the Sichuan Quake 193
bfwebster writes "An article in the Telegraph (UK) raises an interesting question: was the massive (7.9) Sichuan earthquake that wracked China last year and left millions homeless caused by ground stresses following the completion of the Zipingpu dam? As the article notes, 'The 511-ft-high Zipingpu dam holds 315 million tonnes of water and lies just 550 yards from the fault line, and three miles from the epicenter, of the Sichuan earthquake. Now scientists in China and the United States believe the weight of water, and the effect of it penetrating into the rock, could have affected the pressure on the fault line underneath, possibly unleashing a chain of ruptures that led to the quake.'" The Sichuan region is earthquake-prone, but has not seen anything as large as the 7.9-magnitude quake for perhaps millions of years. The Chinese government denies any connection between the dam and the earthquake and seems to be actively obstructing the access of scientists who want to investigate. The article concludes, "There is a history of earthquakes triggered by dams, including several caused by the construction of the Hoover Dam in the US, but none of such a magnitude."
It would have likely occurred anyway (Score:5, Interesting)
As with all things geological, there are a lot of unknown variables, hence the "could", "might" and other diluting terms.
Re:It would have likely occurred anyway (Score:5, Interesting)
Re:I feel a bad movie based on this where need to (Score:5, Interesting)
Sir Ranulph Fiennes (the famous arctic explorer, among other things) was actually kicked out of the SAS for destroying a dam using stolen explosives. You can google for more detailed accounts of the story, but here's one:
http://www.independent.co.uk/student/career-planning/getting-job/my-first-job-explorer-sir-ranulph-fiennes-was-an-sas-officer-420601.html [independent.co.uk]
the government is blameless (Score:4, Interesting)
let's say they know dams cause earthquakes. ok, so there will be some minor earthquakes. but 7.9? no one is going to predict anything that large
still, let's assume the dam is still the trigger for the 7.9 earthquake. emphasis on trigger. its going to happen someday anyway
if they never built the dam, we'd be talking about the 7.9 or 8.3 sichuan earthquake of 2031 or 2102
Re:Prediction (Score:5, Interesting)
not to dodge your sarcasm, but the scientific findings are vague enough to blame the entire quake on Bush bombing people in iraq.
you never know what that one last MOAB will really do what with the butterfly effect and everything.
also if a quake hasn't happened in a million years then it just might be under a lot of stress, that doesn't easily go away.
Re:Prediction (Score:4, Interesting)
Oh yeah, I was of course sidestepping the issue of "Is the finding ACTUALLY valid." Somewhat like what the chinese government will do, only they probably won't do it with sarcasm. It'd be refreshing if they did though.
How do they know it's never happened before? (Score:5, Interesting)
Would a 7.9 quake, although large by earthquake standards, even leave evidence that lasted more than, say, 1000 years? You might be able to tell if you took a cross section of the entire fault line, I suppose, but not all fault lines are known. A L.A. city geologist found a previously unknown (but not currently active) fault under the house of a friend of mine when he was having some drainage work done; new ones are discovered all the time.
Re:It would have likely occurred anyway (Score:4, Interesting)
Or made it much more intense. Maybe without the dam and lake instead of one large earthquake it would have been a series of smaller earthquakes.
Adding a large weight almost on top of a fault is definitely going to influence it, flexing the Earth and altering the stresses in the fault.
Re:It would have likely occurred anyway (Score:4, Interesting)
true, yes the damn may have caused the earthquake, but the proper way to look at it is the earthquake brought the geology back to a neutral point. so technically they should be in a good place.
plus the fact the damn did not fail, says it was built properly.
Just Wait (Score:2, Interesting)
If this is true, then just wait until the Three Gorges begins to top off (it has been filling for years now and has some time to go.)
Re:It would have likely occurred anyway (Score:5, Interesting)
but the proper way to look at it is the earthquake brought the geology back to a neutral point
Why on earth would you say that? Earthquakes don't bring geology to neutral points. They happen when the earth gets past critical point.
I can't think of a totally slashdot car analogy, but here is a good analogy of earthquake causes and how it works geologically that at least includes a car.
Think of a piece of bungee cord 10 meters in length. You tie one part to the tow-ball of a car, and hold the middle of the cord. This means there is five meters of slack cord past the point where you are holding. Now, the car very very slowly starts to drive away from you, and the tension in the cord slowly grows. You holding onto the cord with all your might represents the pressures on the fault line. Sooner or later however, the pull on the cord will be too much, and it will slip in your hand. Now, you don't totally let go however. It might slip an inch or two, just barely enough so that the force of your hand holding it once again overcomes the force of the pull in the cord - but there is still a lot of tension in the cord. When the car moves away far enough again, there will be another slip of a small distance again and again.
This is how fault lines work. When there is a quake, it doesn't go back to a neutral point. It goes back to a point which is lower than the critical point that caused the earthquake.
Re:How do they know it's never happened before? (Score:4, Interesting)
Yes, it would. Off the top of my head, I can think of two classic examples in the US easily visible to regular people, the San Andreas fault and the thrust fault that forms the steep eastern face of the Grand Tetons. In each case, it's easy to figure out how much the fault has moved each time an earthquake occurs. For example, the San Andreas fault slides sideways during an earthquake and displaces streams and geographical features. I believe that they can trace to some degree the earthquake record for the past few thousand years. Similarly, the face of the Grand Teton mountains lifts after each major quake, exposing a fresh patch of earth and rock. I dimly recall they have dated these giving an estimate of a magnitude 7 earthquake every 400-700 years.
My belief is that if the geological record for earthquakes were studied properly, we would find that a magnitude 7.9 earthquake is indeed typical for that particular fault (much less the area). It's quite possible that the dam was the trigger for the quake, but it's not so likely that it amplified the energy release of the quake. If it did, however, I would guess wildly that the mechanism would be reduced energy loss to friction.
NASA math at work. And yes,IAANB* (Score:5, Interesting)
Maybe they can get this drilling crew on the mission to save the day! [youtube.com]
All humour aside, most people have no clue about the energy levels and destructive power available to natural forces, just on our world. (ie:water) Even engineers can fall prey to their preconceptions at times, if they are not diligent. Water is a powerful force, in scale.
Most people perceive the Earth as a solid/stable surface to build on(dig to 'bedrock' for the foundation, etc...), frequently forgetting Earth more resembles a poultry egg: relatively thin shell covering/encasing a liquid center...and just as fragile on scale.
At our most terrible destructive level available technologically to humans today, we are still just 'wannabe' punks in the big picture. Actually, I would argue that communication tech is the most powerful weapon/tech we have devised to date.
*(IAANB) I Am A NASA Brat![clarification of subject line]-just could not pass this one up. And NOT trying to pick on engineers, who have demanding job requirements, but there is a good reason to put erasers on pencils! :-)
Sorry if this was more than you bargained for trying to make a 'funny', but you did raise a valid point! :-)
Re:It would have likely occurred anyway (Score:5, Interesting)
Suggest you better research the coffee spill incident. Car wasn't moving, complaints about temp filed more than once, much hotter than surrounding area restaurants, woman required skin grafts to repair damage and only sued for cost of medical bills after McD's blew her off. Lots of details glossed over concerning that incident but considering just how hot it was and the damage it did I don't think awarding ONE day's worth of coffee sales was that bad of a restitution... and that was later overturned.
There are certainly shitty lawsuits but THAT one was pretty deserved I think and a poor example despite your trying to be funny about it.
Re:Prediction (Score:5, Interesting)
Yes, that's so true. The changes that China has gone through in the last 100 years are staggering. Edgar Snow's Red Star Over China [google.ca] gives a fantastic account of what China was like during the Communist Revolution. It brought them forward a millennia in a few years, spreading education, and raising standards for 100 of millions of poor Chinese peasants. But that still left China far behind what we consider a well developed country. Of course, the Great Leap Forward and Cultural Revolution didn't really help. Then again in the last ten or fifteen years, it's almost as if China has come forward another millennia, where cities like Shanghai are fairly easy to live in as Westerner. The people there are now beginning to resist change for this reason. Want to build a new Maglev line to Hangzhou or high speed rail link to Beijing? The people organised together and forced the government to re-route it via somebody else's neighbourhood. Out in the country though, people still put up with being relocated because their lives haven't changed as fast and are some way behind.
Re:It would have likely occurred anyway (Score:4, Interesting)
It could also have resulted in the stress being accumulated faster than the normal release mechanisms could offset. The FA suggests that the stress was roughly "25 times the normal tectonic movement for a year" - so instead of having a dozen or so non-damaging quakes every couple of years, they got one big one.
Who knows? Too many variables...
Re:Social justice requires desalination (Score:3, Interesting)
Of course, preventing flooding of flood plains wrecks the ecology and in many cases has resulted in the severe degradation of the arable land downstream.
A more sensible solution would be to not build towns and cities in flood plains. But it's a bit late for that.
Paeleoseismology (Score:4, Interesting)
Paleoseismology as you described is actually quite difficult. In the case of the San Andreas, you can't really look at off-set streams and such. You can rarely discern more than one or two events along such offsets, and once you do, it is very difficult to determine the age of the offset. You can get the amount that it's moved, yes, but not the timing. Worse, since you don't know the timing, you don't know if the offset is from one or more events.
The way it's done for strike-slip faults like the San Andreas is to look at a cross-section perpendicular to the fault, looking for layers of material off-set (or suddenly changing thickness, etc.) along the fault. The best way to date those layers is through carbon-14 dating of organic material, which can give you accuracy only within ~1-200 years - and that's assuming that the organic material you date is not from elsewhere, is not from 200 year old trees, etc. If an event offsets every layer from the bottom up to a certain point, you date the top layer that it cuts through to get a maximum age, and the layer that it didn't cut through is the minimum age.
You can imagine the difficulty and ambiguous nature of this. The individual layers that you have to recognize and date are on the scale of centimeters to decimeters - I've seen some of the areas that were used, the famous one being along Pallet Creek which is along the San Andreas northeast of LA (I have a picture of it - well, it is a picture of a girl standing in front of it - here: http://www.flickr.com/photos/penguinchris/3037578910/ [flickr.com]) Here, luckily there was constant, relatively rapid deposition of material. In most places this is not the case, so any record of movement on the fault is eroded away.
For the San Andreas, we have a partial record going back ~1500 years. There really is no reliable way to reach back further than that - the record isn't normally visible in older rock units. Looking at the larger-scale structures is interesting by itself but doesn't tell you anything about when specifically there was movement. The fault system in the Sichuan region is fairly well understood - it is a kind of combination strike-slip/thrust fault (see http://quake.mit.edu/~changli/wenchuan.html [mit.edu] for some nice diagrams.) But I want to call BS on the idea that they have any idea how frequently major earthquakes have happened there - and even if they do, the idea that it is "perhaps millions of years" since the last one is ridiculous no matter what.
And then, when you *do* figure out a approximate year for an earthquake, how do you determine how big it was? Again, extremely difficult! The best estimates come from comparing old written records of destruction with those from modern earthquakes - nothing scientific at all!
What's being done extensively with the San Andreas is physics-based computer modeling - we have some idea of the force building up, and combining that with records of historical earthquakes we can make an estimate of a major earthquake every ~150 years. But even for this, the best-studied earthquake area, it's not much more than a guess.
I don't know as much about the Teton fault (other than that it is a normal fault, not a thrust fault as you stated ;) ) but I'll comment on the idea of a "magnitude 7 earthquake every 400-700 years." These kinds of estimates are based on the very difficult work I described earlier (and I'm not sure how much has been done for the Teton fault) and whatever geologist came up with that would probably admit it is a simple guess without much to base it on. I mean, think of it - is knowing there's a large earthquake every 400-700 years really all that useful anyway?
By the way, I assume any dating of the Teton fault would be done this way: when new patches of rock are exposed along the fault as you described, they start getting hit by cosmogenic radiation. By measuring the amount of cosmogenic radio isoto
Re:It would have likely occurred anyway (Score:2, Interesting)
The waste water injection that they did at the Rocky Mountain Arsenal in Colorado is a well known example (several decades old though). See here: http://www.nyx.net/~dcypser/induceq/iis.html
Re:Social justice requires desalination (Score:3, Interesting)
>Dams prevent catastrophic, uncontrolled flooding by buffering the surge in a lake and letting it out slowly.
As long as they're big enough. If they're not, a rapidly increasing flood of water, that if left uncontrolled might rise at 2 feet an hour, flooding many houses, could be turned into a 20 foot high wall of water, debris, and rock from washed-out dams [super70s.com] that kills 145 people rather than just destroying a bunch of houses.
Every "flood control structure" on that river got ripped out. A flood that had almost the same rainfall 40 years earlier didn't kill anyone because it took two hours to go from heavy runoff to full flood. My friends that were down in the canyon in the 1976 flood said the front wave of the flood was moving at about 60mph and consisted mostly of a mass of mobile homes (with the occupants still in them.)
Re:It would have likely occurred anyway (Score:2, Interesting)
Car wasn't moving,
She was a klutz. That's McDonald's fault?
complaints about temp filed more than once,
So? Hot coffee is *hot*. If you don't like how hot their coffee is, *don't buy it*.
woman required skin grafts to repair damage
And if she hadn't put the cup between her legs with the *lid off*, it never would've happened. Meanwhile, the grafts were required specifically because she spilled the coffee between her legs, while in the car, leaving her to sit in it. Is that McDonald's fault? I think not.
only sued for cost of medical bills after McD's blew her off.
As they should've. She spilled *hot coffee* on herself. Coffee she willingly purchased and *knew* was hot. And it's McDonald's fault it was hot and she spilled it on herself? I can't think of a more retarded lawsuit.
Lots of details glossed over concerning that incident but considering just how hot it was and the damage it did I don't think awarding ONE day's worth of coffee sales was that bad of a restitution
On the face of it, no. But it sets a precedent that they were prefer not to set. After that, if someone scalds their mouth on hot cheese, should McDonald's hand out coupons for a free burger? They did it for the coffee lady...
There are certainly shitty lawsuits but THAT one was pretty deserved I think
And I think not. She bought coffee she *knew* was hot. She then took off the fucking lid. And then *put it between her legs*. How is that anyone's fault but hers?
Sorry, bub. If I cut my foot off with a chainsaw I don't sue the chainsaw manufacturer. This is no different. She was handed a hot coffee that was advertised as such, that she *knew* was hot, and then did something really fucking stupid with it. It's her own damn fault, and the idea that McD's owed her millions because of her stupidity is *disgusting*.