Science and technology
Disaster prevention
Difference Engine: Whole lot of shaking
Sep 2nd 2011, 7:19 by N.V. | LOS ANGELES
DRENCHED and battered by Hurricane Irene, and facing a clean-up bill pushing $10 billion, residents on the east coast of America have understandably had more on their minds over the past week than the earthquake which struck the Piedmont region of Virginia a day before the tropical storm swept ashore. Yet, the shaking caused by so modest a tremor, at such distances from the epicentre, caught experts by surprise. In the long term, the Virginian earthquake could trigger a bigger shake-up in disaster precautions at nuclear-power stations in America than even the Japanese catastrophe at Fukushima.
The magnitude 5.8 quake that struck 38 miles (61km) north-west of Richmond was felt as far west as Wisconsin, as far south as Atlanta, Georgia, and as far north as Montreal, Canada. Damage was reported over 300 miles away in Brooklyn, New York. The White House, the Capitol and other buildings in Washington, DC, had to be evacuated. Cracks were even detected in the Washington Monument—the tallest stone building in the world—which is now closed indefinitely. Washington National Cathedral lost capstones from three of its spires, and cracks were found in several of its flying buttresses.
All this from a seismic event that would barely rate as an after-shock in California. Earthquakes on the West Coast are more frequent and can pack a much greater punch. Size for size, though, their rattlings are rarely felt at quite such distances.
Put that down to the difference in the age of the rocks. As the relatively young Pacific plate dives beneath the continental land mass, sudden slippages along the grinding rock faces breed swarms of earthquakes, big and small. But the majority of shockwaves so created quickly dissipate as they run into fractures and hotter rocks deep beneath the surface.
Subjected to stress, rocks above 300ºC or so tend to flow rather than rupture. And because fluids cannot handle shear forces anywhere near as well as solids, the potent S-waves from an earthquake (the secondary, or shear, waves that shake the ground from side to side and knock down buildings in the process) eventually fizzle out. An earthquake’s faster-moving P-waves (primary, or pressure, waves that push the ground longitudinally) get through, but they carry far less energy and do little damage.
By contrast, the crustal rocks that created the Appalachian and Allegheny mountains in the east of the country, being hundreds of millions of years older, have had ample time to cool down. In the process, they have become denser and harder. Unlike in California, seismic activity on the East Coast is usually shallow and well away from the boundaries where tectonic plates collide.
As a result, earthquakes in bedrock east of the Appalachians tend to ring the earth like a steel girder being struck with a hammer. West of the Rockies, the effect is more like a rubber tyre bouncing over a pothole. All told, eastern earthquakes can shake areas ten times greater than comparable western ones.
And they do so at much higher frequencies. That makes a big difference to the kind of damage done. The lower-frequency vibrations in California cause greater damage to large, rigid structures such as office blocks, bridges and elevated highways. They might even rent a nuclear reactor’s containment vessel were a major seismic thrust to occur on a nearby fault.
One of the two nuclear power stations in California, at Diablo Canyon, near San Luis Obispo, is only a few hundred yards from an active fault which, coupled with an even bigger one three miles away, has the potential to produce a magnitude 7.3 earthquake. Recall that the quake which jolted Japan’s (and the world’s) largest nuclear-power station, at Kashiwazaki-Kariwa on the Japan Sea coast, in 2007, was a more modest magnitude 6.8 (see “Shaken, but not stirred”, August 10th 2007). The damage there was such that three of the station’s reactors remain shut to this day. Until the Fukushima disaster, Kashiwazaki-Kariwa was Japan's biggest nuclear accident.
By contrast, the higher-frequency shaking that takes place east of the Appalachians implies longer-traveling shockwaves of shorter wavelength. While such shocks are unlikely to topple multistory parking structures, flatten apartment blocks or toss freeways in the air (as happened in Los Angeles during the magnitude 6.7 Northridge earthquake in 1994), they can play unexpected havoc with delicate instruments and electronic devices.
This explains why the pair of reactors at the North Anna nuclear-power station, ten or so miles from the epicentre of last week’s earthquake in Virginia, were knocked offline. Sensitive relay switches, used to protect the plant’s transformers, seem to have interpreted the earthquake’s high-frequency shaking as an electrical spike coming down the line, and switched off the power supplied from the grid for running the plant.
As a result, the reactors had to be immediately “scrammed” (ie, shut down rapidly by ramming neutron-absorbing control rods into the core to kill the nuclear reaction) and emergency generators fired up to provide electricity for cooling pumps and other safety equipment. One of the diesel generators malfunctioned—a disturbingly common problem, apparently, at nuclear power stations, and one of the key underlying reasons for the disaster at Fukushima. Fortunately, the remaining three standby generators functioned properly. No damage to the plant was reported, other than cracks in ceramic insulators on one of the transformers.
Even so, the Virginia incident has triggered calls for fresh scrutiny of the dozens of ageing nuclear reactors in the United States. The majority were constructed to standards designed to survive conditions more common in the west of the country—despite the fact that only eight of the 104 remaining reactors in America are west of the Rockies. Most were also built before the oil industry’s modern 3D seismic techniques started discovering active faults no-one previously knew existed.
The day after the Virginian earthquake, Edward Markey, a Democratic congressman whose district includes the Massachusetts Institute of Technology and Harvard University, as well as a big chunk of the East Coast’s high-tech industry, wrote to ask the Nuclear Regulatory Commission (NRC) whether the earthquake had exceeded the seismic safety specification the North Anna plant had been built to.
Mr Markey also urged the NRC to embrace the recommendations of its own “Near-Term Task Force" on Fukushima, which the NRC has continued to drag its feet on. In a recent report (“Fukushima Fallout”) produced by his own office, Mr Markey noted that the NRC had failed to incorporate its technical staff’s recommendations, despite the fact that new information indicates a much higher probability of core damage caused by earthquakes than previously thought.
Based on seismic data from 1989, the NRC expects the number of events causing damage to a reactor’s core to be an incredibly minuscule 0.0000038 per year—equivalent to a reactor failing, on average, once every 260,000 years. However, reworking the numbers using seismic data from 2008, and computing the risk for the whole fleet of reactors in America being operated for the further 20-year extension being sought for their current licences, Mr Markey’s staff expect the risk to increase 7,000-fold to a probability of 0.026 per year—ie, one nuclear disaster somewhere in the country every 38 years. In short, another Three-Mile Island some time between now and 2049.
If that is indeed the case, it is surely time for the NRC to embrace, rather than resist, the lessons of Fukushima in general, and North Anna in particular. Rightly or wrongly, NRC’s foot-dragging on regulatory reform has given the impression of favouring industry interests over public safety. That is neither in the best interest of the nuclear industry itself, nor the public’s need for cheap, carbon-free power.
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Earthquakes are too common all around the world. Yes in Virginia that is rare because the east coast is not an active tectonic region. With properly built safety features in all buildings earthquakes will not have any effects on the architecture and only the damage will come from after math events. With advances in research and technology in the field of architectural structures in civil engineering will make and has made a safer present and future.
Earthquakes are too common all around the world. Yes in Virginia that is rare because the east coast is not an active tectonic region. With properly built safety features in all buildings earthquakes will not have any effects on the architecture and only the damage will come from after math events. With advances in research and technology in the field of architectural structures in civil engineering will make and has made a safer present and future.
I guess the east coast should take more precautions when it comes to earthquakes. If a 5.8 quake is felt in Canada, imagine what a large earthquake would be like on the east coast. I certainly don't want to experience the nuclear plants failing.
It was really interesting learning about the difference between the land faults on the east coast and west coast. The land is more solid on the east coast.
I live in Virginia and I barely felt this earthquake. I guess D.C. felt it a lot more than southern Virginia. I had no idea that it cracked the Washington Monument!
I guess the east coast should take more precautions when it comes to earthquakes. If a 5.8 quake is felt in Canada, imagine what a large earthquake would be like on the east coast. I certainly don't want to experience the nuclear plants failing.
It was really interesting learning about the difference between the land faults on the east coast and west coast. The land is more solid on the east coast.
I live in Virginia and I barely felt this earthquake. I guess D.C. felt it a lot more than southern Virginia. I had no idea that it cracked the Washington Monument!
Being from Virginia, this flurry of natural disasters is a sobering reminder as to how much man can and cannot control. I believe in every situation, safety is first. It seems as though the nuclear power stations and reactors have the proper precautionary measures in place, but it is imperative that these be monitored into working order at all times, or else these measures are pointless. It's great to hear that numerous nuclear reactors were shut down by default by various censors that detected the rather mediocre Virginia earthquake shocks, but we must make sure that every nuclear plants' censors are to working order. Mr. Markey's findings/calculations need to open all of our eyes to how seriously we need to handle our implemented safety measures, as well as improve on them.
I do not think that it would be very difficult for Congressman Markey to obtain the seismic safety specification for the North Anna plant. That facility alone has gone through so much testing that there would be many documents about all sorts of specifications. Justifiably, he is responding to his many constituents about fears of nuclear plant disasters ever since the widely reported nuclear reactor incidents at Japan.
Though, if he wants the NRC to change regulations it will prove much more difficult. Normally, regulations about complex systems (such as nuclear plants, etc.) are constantly re-examined, edited, and changed to ensure safety above all else.
After this recent "unexpected" earthquake on the east coast, Geotechnical and Structural engineers should be hard pressed to re-evaluate the standards and building codes set forth to withstand seismic activity. I believe the standards need to be raised to a higher margin of safety for future concerns. Granted that it is hard to predict the future, we need to consider extreme possibilities when designing the "infrastructure of tomorrow." How much money and energy are we losing from the North Anna Nuclear Plant shut down? It might be petty in the grand scheme of things, but overtime it adds up. We need to figure out where we are headed with nuclear power and then design for extreme scenarios...
The epicenter was a few miles from my permanent residence, but I was across the state at the time and barely felt anything, I thought a large truck was just passing by for a few seconds.
Back home my family said it was very surprising, buildings were evacuated and nobody knew what to do, my friends in NJ said they even felt some of the shock.
Nuclear energy is so efficient and really is safe, its unfortunate the world is so so cautious about it. For example Angela Merkel deciding to shut down existing plants in Germany. We should focus on making the reactors even safer rather than just abandoning the idea.
Solar, wind, ocean current energy sources are nice... but will most likely NEVER be enough to power our grid, ever.
At first I thought people were over-reacting to the earthquake, especially since I didn't feel it or see any damage from it. That's probably how people on the West Coast felt about it, since it "would barely rate as an after-shock in California." The description of how the land differs from coast to coast helps people to understand that this earthquake really was a big deal that damaged quite a bit of property.
The effects were so much greater on the east than they were on the west also due to how differently the buildings are constructed. Californians know there are many earthquakes so they build stronger structures. Maybe we should implement their designs all over the country? It might take a lot of money to do this, but it would probably save more in the event of an earthquake, or even other disasters.
If theres a higher risk of nuclear disasters, one every 38 years, then why aren't we taking the extra steps to prevent them? A little money now will save a lot of money later. The US should take this rule and live by it
How many people in the US have died from a Nuclear Related Disaster in the US: 0
That being said, nuclear energy does have its downside regarding the disposal of the spent nuclear material, but it does not the same brute environmental impact of burning coal. If the plants were made correctly, there really shouldn't be an issue on the East Coast at least because there is not much earthquake activity here.
I barely felt the earthquake where I am at in Virginia and my parents felt their first earthquake in the their lifetime of about 50 yrs. It is always good to go back and re-look at the infrastructure of the nuclear power plants for the future and improve them because eventually most of our energy will have to be nuclear due to the fact that we will run out of resources for oil.
The recent quake was a shock to everyone I know because the epicenter was right in the middle of where i'm from and I had correspondence with friends all across the state about their experience with it. The fact of the matter is that no one was hurt and that there was little to no damage at all. And we can accredit this to the fact that america has a great infrastructure and building codes, because if you compare this quake to other ones, the places with good economies tend to have strong infrastructure as well.
I think the most important thing that comes from this disaster is the worry about nuclear power plants. There are about 100 power plants in the US and over 400 around the world. There are also at least 50 more being built right now. I don't now why nuclear power plants continue to be built. As we can see by this article, an earthquake or other natural disaster can happen at any time and anywhere. The dangers of a nuclear power plant explosion are immense. Not only will people die simply from the explosion, but the chemicals coming from this plant will cause serious defects and/or death as well.
With all of the technology we have today and all of the alternative resources for energy, there has to be a more effective and safe way to produce energy . Although there has never been a death caused by a nuclear power plant disaster, there is always the possibility and i think that this shows that we should be more cautious about what we build in our country.
I think too much emphasis is being put into how nuclear power stations are outdated or at risk for failing. There has been only one nuclear disaster in the United States in the decades that nuclear power stations have existed and there were no fatalities. Most buildings built within modern building codes in the last 20 years can handle earthquakes, the thing that people overlook is that when looking at past earthquakes elsewhere and their effect on people and structures is that the resulting tsunami was the cause for most of the cost in human life and damage, not the actual quake itself.
Since on average there is a nuclear disaster every 38 years, governments should start considering which one is more important, money spent to prevent that from happening from stronger buildings or money spent after a nuclear disaster occurs. The healing process after one of these disasters costs more then just a lot of money, due to all the tragic losses.
After the earthquake in virginia, nobody died. The earthquake did not do much harm compared to earthquakes in japan. The modern house codes we have now survived the earthquake. Enforcing building codes to houses now after an earthquake that did not do much to us would be a waste of money. Japan and other places in the country have structured their buildings due to the occurance of earthquakes they get every year.
Virginia RARELY gets earthquakes according to "virginiaplaces.org"
while on the other hand Japan gets up to 1,000 earthquakes a year
nuclear pants are getting sfer 10 times every decade, of course shutting off the oldest plants is advisable- but it is exactly the "success" of our greenies that no new plants have been constructed/new designs approved.
it makes sense, at least pollitically: if you rage a jihad against nuklear plants, be shure that the possibility of a catastrophe is there..
to be that cynical-
In the history of nuclear power in the USA, not a single person has died. Nuclear is clean, its recyclable and far more efficient than fossil fuels. Sure, disasters have occurred around the world dealing with nuclear energy, but if the US learns from those disasters and fixes the problems that caused them (like the diesel generators) then I don't see why nuclear energy can't continue on and be the predominant source of energy in the US. France is making it work, so why can't we?
The earthquake hit Virginia did not cause panic maybe because it is not a big deal compared to the huge earthquake happend in Japan.
Japanese suffer earthquake every day, the feel normal about it. Most of their builings are strong enough to get over the hardest earthquke because that is the main task for them. However, the huge earthquke happened off the coast, and made the main keller the tsunami. Even though their hoses are stronger than anyother country, they still can hardly survive in the huge tsunami.
The earthquake happened in China earlier caused thousands of death. The reason may because the density of population is higher than other regions, but the main reason is that the earthquake happened in the mountain area. There was nothing people can do when mountain arround them were collapsing.
Although newly technology can privent some natural disasters and reduce the loss maybe, people still in risk of some sudden catastophies.
"Earthquakes in bedrock east of the Appalachians tend to ring the earth like a steel girder being struck with a hammer. West of the Rockies, the effect is more like a rubber tyre bouncing over a pothole. All told, eastern earthquakes can shake areas ten times greater than comparable western ones."
Having lived on both the east and west coast, this statement couldn't be more true. The west coast expects and even plans for earthquakes but the east coast very rarely experiences them so when one does occur, people don't know how to react. People can only prepare for earthquakes to a certain extent. Enforcing stricter building codes and having more precautions for all natural disasters make an impact but there will always be an unpredictable and uncontrollable element.