However, knowing that the levees protecting NewOrleans are primarily composed of dirt, the possibility of soil liquefaction during an earthquake does call into question the wisdom of resettling areas which were flooded by HurricaneKatrina.
posted
I couldn't believe this. I had to call my boyfriend and tell him. I live about 40 miles from where it happened I didn't feel anything. I just couldn't believe that Louisiana had earthquakes. He had to explain about the fault lines nearby.
Posts: 1733 | Registered: Apr 2005
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posted
My conversation with someone who is there right now:
teacup killer: hey, did you know there was an earthquake today? Ace: in L.A.? Ace: Frisco? teacup killer: 43 miles from New Orleans' city center. Ace: an earthquake in New Orleans? teacup killer: Yes. Ace: nope I missed it teacup killer: You didn't notice anything? Ace: what time was it? teacup killer: 6:52pm. Ace: must not have been that serious teacup killer: You didn't notice it? Ace: no...and I was sitting in a trailer..I would have felt it
posted
last one we had (indiana) I remember thinking the cat hit jumped on the couch, but he didn't, so I just stopped caring till I heard about the quake on tv.
Posts: 5362 | Registered: Apr 2004
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*giggles* That's not an earthquake, that's a hiccough! *never notices anything less than about a 4.5*
Posts: 21182 | Registered: Sep 2004
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We've had earthquakes here (New Hampshire). Last one I recall happened when I was seven and my father thought my younger sister and I were shaking his chair and kept yelling at us.
Of course, we were in the kitchen the entire time, while he was in the living room.
Posts: 14745 | Registered: Dec 1999
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I felt a tremor in Yellowstone once. It was like an electric shock. That's all my experience with earthquakes.
Posts: 5957 | Registered: Oct 2001
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My 5th grade teacher was out for three days after the Northridge earthquake. Her apartment had collapsed on her.
And then for a week after that, she brought her 4-year-old son to school for a week and he had to sit in the corner and draw or listen to tapes on headphones, while she found a new preschool for him-- his had been structurally damaged and was declared unsafe.
All we had was a broken mirror-- my mom forgot to bolt it when she was doing the rest of the large furnishings after we moved in-- and some books that fell off shelves because we always forgot to put the bunjee cords that held them in back on the shelves that we used most often. But then, where I lived, we were a bit further away from the epicenter (my teacher lived in Northridge, proper) and sat on solid granite bedrock. It was still enough shaking to wake us up, though.
Posts: 21182 | Registered: Sep 2004
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posted
Apparently, the "extremely minor" earthquakes can't be ignored by Lousiana citizens. I ran across this info back in December, but failed to post it in this thread. And have just posted it in the GlobalFlooding thread. So for those who might be interested who didn't catch it there...
1) The diversion of the Mississippi for flood control and into a concrete shipping channel has stopped the deposition of new soil on the Mississippi delta. Because of this, there is no replenishment of the large area of Lousiana's tidelands being washed away by normal ocean wave action. 2) Shipping channels dredged through Lousiana's barrier islands, tidal marshes, etc are allowing those ocean waves to penetrate deeper and faster, which causes faster stripping of soils along the Louisiana coastline. 3) There is the probability that GlobalWarming will cause a rise in sea-level by a minimum of 1foot/0.3metres within the lifetime of most of the people posting on this forum. With the aforementioned remote possibility that it could be as much as 20feet/6metres within the lifetime of Hatrack's toddlers.
Even excluding GlobalWarming effects, the coastlands south of NewOrleans are going to be underwater within ~50years. Those mini-earthquakes that Louisiana has been experiencing have been due to a subsidence fault offshore southward in the Gulf of Mexico. Essentially the entire Lousiana coast south of the line heading west from NewOrleans appears to be sliding down into that fault in the process of becoming a part of the Gulf of Mexico. If you take a look at the predicted subsidence on the Lousiana elevation map at the bottom of page8, about half of the coastal area less than 3feet/0.9metres above sea-level will be underwater by 2050, with the rest being underwater by 2100.
If you compare that elevation map to this state map, LakeCharles, Lafayette, and BatonRouge will nearly be seaports by 2100. And NewOrleans will be an island city walled off from the Gulf of Mexico, connected to the mainland by a narrow strip of land between the MississippiRiver and USHighway10. ie Even excluding GlobalWarming, what would be now be a seawall capable of protecting NewOrleans from a Category5hurricane would probably only afford protection from a Category3hurricane in 2100.
posted
I lived in Taiwan for 2 years and I tallied about 5 seperate earthquakes. They ranged from a single moderate shock, to prolonged rumbling. The scariest feeling in terms of earth quakes for me is being at the top of a tall building as the quakes cause the top to sway back and forth quite literally. All you can think is "Ok, if this building falls I will probably die." I actually lived in the epicenter area of the 9/21 earthquake that Taiwanese people all still talk about. There is still alot of residual damage and they even have a museum with an earthquake simulator. I always wondered, what happens if an earthquake strikes while you are in the simulator?
Posts: 14316 | Registered: Jul 2005
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"I always did want to own a place on the beach of an island..."
Après moi, le déluge, neh? Nice when ya can get the rest of the US to pay for it. For the price of building a seawall that would now* protect NewOrleans from a strong category4 / weak category5 hurricane, it would be cheaper to buy an inland Lousiana home for each&every NewOrleans evacuee. But you are right. What with "campaign contribution"s, welfare payments for the rich is much more likely to occur.
* ie Excluding future subsidence and GlobalWarming effects.
posted
Take a look at the US coastal elevation maps. Are you suggesting that the US should build a seawall from the southernmost point of Texas all the way to the northernmost point of Maine? And keep building them higher should GlobalWarming cause a sea-level rise? What are you going to do with the rivers/etc behind that seawall? Pump their waters over the seawall into the ocean? Or use that freshwater accumulation to make lakes behind the seawall, drowning the current coastline under SaltonSea-like brackish water instead of seawater?
posted
Apparently I've been sleeping right through these earthquakes.
On the bright side, though, it looks as though my house in Lafayette and my parent's house in Hammond will be prime real estate before too long.
Posts: 5462 | Registered: Apr 2005
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posted
The New Madrid fault runs through the U.S. southern states, and about 200 years ago, produced one of the most devatingly powerful earthquakes in history. The terrain of the whole area was drastically rearraged. The earthquake is supposed to strike every 400-500 years, but no one can say for sure it cannot come sooner. When it hits, it will cause as much damage as "the big one" long predicted for California.
quote:THE NEW MADRID FAULT SYSTEM EXTENDS 120 MILES SOUTHWARD from the area of Charleston, Missouri, and Cairo, Illinois, through New Madrid and Caruthersville, following Interstate 55 to Blytheville and on down to Marked Tree, Arkansas. It crosses five state lines and cuts across the Mississippi River in three places and the Ohio River in two places. .... THE GREAT NEW MADRID EARTHQUAKE OF 1811-1812 was actually a series of over 2000 shocks in five months, five of which were 8.0 or more in magnitude. Eighteen of these rang church bells on the Eastern seaboard. The very land itself was destroyed in the Missouri Bootheel, making it unfit even for farmers for many years. It was the largest burst of seismic energy east of the Rocky Mountains in the history of the United States and was several times larger than the San Francisco quake of 1905. .... A MAJOR EARTHQUAKE in this AREA, 7.5 or greater, happens every 200-300 years (the last one in 1812). There is a 25% chance by 2040. A New Madrid Fault rupture this size would be felt throughout half the United States and damage 20 states or more. Missouri alone could anticipate losses of at least $6 billion from such an event.
posted
aspectre, we need a lot of port services at the entrance to the largest river on the continent, and they need to be manned by people who don't live a 2 hour commute away. How on earth could we not rebuild New Orleans? Quite apart from the history, we simply need a city there.
Posts: 6246 | Registered: Aug 2004
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The New Madrid quake moved the land enough that it caused the Mississipi to flow up river for a time.
Posts: 12591 | Registered: Jan 2000
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Exactly Anne Kate. New Orleans was built where it was built for a reason. It has the only true deep water port in the US. The disadvantages of building there are obvious, but they simply didn't outweigh the advantages 3 centuries ago and they don't outweigh the disadvantages now.
Besides that, a magnitude 3 earthquake is nothing.
Posts: 12591 | Registered: Jan 2000
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posted
Okay, just have to reply to the original post, though it might have been answered already. First, there chance of a magnitude 3 earthquake causing anything to liquify is so absurd it's laughable.
Second, I'm not sure what the significance of the levees being made out of soil has to do with anything. Any soils engineer worth their salt will design a levee that won't liquify internally. The dangers of liquefaction lie in the ground underneath the levee. And there's just as much danger of a floodwall failure in that case as there is of a levee failure, probably more, since floodwalls can't take the deformation that a soil structure can.
Posts: 609 | Registered: Apr 2003
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posted
The NewOrlean levee soils did liquify internally from hydrostatic pressure alone, even without an earthquake. That's why the flood walls topping them tipped over and flooded the city. The levee at those points might have collapsed anyway: nearby people were reporting that the water was seeping into their neighbohood well before the floodwalls collapsed.
quote:A 1998 ruling, by an administrative judge for the [Army] Corps' [of Engineers] Board of Contract Appeals, shows that the contractor, Pittman Construction, told the Corps that the soil and the foundation for the walls were "not of sufficient strength, rigidity and stability" to build on... ...There already was an earthen levee made of soil. Embedded in that was a thin metal wall called sheet piling. The contractor was hired to pour concrete on top of all that to form the flood wall. ...the contractor complained about "weakness" of the soil and "the lack of structural integrity of the existing sheet pile around which the concrete was poured." The ruling also referenced the "flimsiness" of the sheet piling... ...The construction company said as a result of these problems the walls were shifting and "out of tolerance", meaning they did not meet some design specifications. Nevertheless, the Army Corps of Engineers accepted the work. ...The judge...blamed the contractor for the construction errors and turned down Pittman's request for more funds. [Nonetheless, Pittman planted the pilings for the flood walls deeper than their contract specified. And probably lost money for doing so, because] Pittman Construction is now out of business.
The 21pages of Pittman's Appeal Hearing has a few other items of interest. (Can't remember the right keywords to google it up, but I think that) There was a followup story in which the news media discovered that the Corps' own engineers had sent in reports to their supervisors that the levee soils&construction were insufficient for the task; well before Pittman was even selected for their flood wall contract. Then were told by their superiors that the work met specifications, to forget about it and let the supervisors handle it Makes one wonder why those supervisors would ignore their own employees' engineering opinions. The Army Corps of Engineers also inspected and certified the rest of the levee sections upon which the current work is being done. Hopefully, with FAR greater professionalism than they have shown on the collapsed sections.
BTW: A magnitude3 earthquake is equivalent in power to an explosion of ~31.6tonnes/~34.8tons of TNT. And as with an explosion, the closer one is to the center, the more one would feel an earthquake. The Whitehall earthquake's center was a fault slip at such a depth and extended over a duration that nobody noticed it except for seismologists. If that fault slip had occurred sufficiently closer to the surface and were of sufficiently short duration, it would have been felt by many locals. If a magnitude3earthquake were even closer yet to the surface, soil*liquefaction could occur; especially in an already water-saturated soil such as that found on the inside of a levee. Not that I am saying that a jolting quake is highly likely in Louisiana, or that a jolting quake is particularly relevant to southern Louisiana sliding into the Gulf of Mexico.
* There are always readers other than the specific person to whom I am responding. So I strongly tend to write&link for those in the audience who may be unfamiliar with the subject.
Also, before I lose them, a couple of links for a later discussion: A map centered between BatonRouge and NewOrleans, with BatonRouge a touch off the map on the upper left corner, and NewOrleans a touch off the map on the lower right corner. And an interactive flooding map of southern Louisiana.
posted
It's funny how stupid people routinely think our ancestors were. I overheard a conversation regarding New Orleans at lunch yesterday, and it largely revolved around the sentiment, "Why were people so stupid to build a city right in the middle of hurricane territory like that?"
Humanity is generally so smug about how clever it is, it cannot imagine not being vastly more clever than previous humans.
Posts: 17164 | Registered: Jun 2001
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posted
aspectre, can you point to where you're seeing that liquefaction was one of the causes of the levee failures? Several modes of failure are believed to have occurred, one of which is seepage under sheet pile walls. This would cause increased pore pressure on the "dry" side of the levee, but not necessarily liquefaction. For liquefaction to occur, the pore pressure has to be great enough to actually put the soil particles in suspension.
I agree with HC (where have you been?) that a 3.0 earthquake is not going to cause liquefaction, but I'm a Florida engineer, so earthquakes aren't my thing. Several years ago, one of FDOT's bridge engineers decided that our bridges needed to be designed for earthquakes. After seeing the costs involved with designing for something that doesn't happen in Florida, they transferred him. Since it was FDOT, that means he was promoted.
quote: Second, I'm not sure what the significance of the levees being made out of soil has to do with anything. Any soils engineer worth their salt will design a levee that won't liquify internally.
Keep in mind HC, that an engineer worth his salt would have also designed the sheet pile walls deeper and used higher factors of safety considering the variable nature of soils around New Orleans. He probably would have also done borings closer together than 300 feet knowing how variable things were. Of course, that's easy for me to say with the luxury of hindsight down here in Florida.
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