Demonstrating earthquake liquefaction in a wheelbarrow

Gnat sez, "A resident of Christchurch, New Zealand, cleverly demonstrates the liquifaction that caused so much trouble in the recent earthquakes. The ground is soil and water, usually stable. When shaken, the soil clumps and water separates out: liquifaction. The result is damaged houses, fallen buildings, and a city of death and mess."

Christchurch Earthquake Showing the sand liquefaction process with vibration (Thanks, Gnat!)

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apoxia

There have been many geologists interviewed on NZ’s national radio station here since the quake. Interestingly, liquefaction happens instantaneously when shaking meets the required amount. The liquid comes out and the soil compacts harder afterwards. Liquefaction has been very localised in areas. In our new house which we are (supposed) to be moving into this coming Friday there is copious silt at one end of the street and none at all where our house is. (BTW, I don’t recommend settling on a house purchase just over a week after a devastating earthquake. Banks and insurance companies have become cripplingly risk averse).

We had very strong winds today in Christchurch blowing this dried silt all over the city in great white choking clouds. I’ve heard estimates that it will take 15 to 20 years to rebuild our city. If you’d like to donate to the devastated people of this city please see http://www.redcross.org.nz/donate
nanoquimico

That would be a neat thing to show in a rheology class. Because there’s too much math, rheology usually is regarded as an abstract, geeky subject, but this kind of phenomena reminds us that the stuff has many real-life implications.
perchecreek

Thixotropy!
Anonymous

Could future disasters be predicted or even averted by systematically taking soil samples from earthquake prone areas and running them across this man’s driveway in a wheelbarrow?
Anonymous

Any and everybody from Christchurch could show you this because this is what happens when you cart a wheelbarrow of silt from the backyard to the road.
Anonymous

Liquefaction is one of my favorite geology words. An easy way to simulate it:

Go to the beach and stand on some wet sand. Mostly firm, yeah? But twist your feet a bit and watch as you sink down into the muck.

Unfortunately, this phenomenon has been ignored in the construction of high end housing in places like San Francisco, where there has been a lot of “new land” created by reclaiming bay. All those houses are on unconsolidated silt, and when their next big quake hits (we know they are overdue for a big one thanks to periodicity) things will get messy.
- Antinous / Moderator
  
  SF already experienced landfill liquefaction in the 1989 quake. That’s why the Marina was devastated while other parts of the city were virtually unaffected. We had the weird experience of having food drives in the Sunset to feed people a few miles away in the Marina.
GreyEminence

Apoxia,

Liquefaction can be primarily considered a function of the following; density relative to critical state, input seismic motion, localized stratigraphy, there are many other factors but I shall only deal with these three.

Density relative to critical state (ie. critical state soil mechancis) describes the physical arrangement of the soil particles with respect to the in-situ effective stress condition. A given relative density may be above or below the critical state line (for a given stress condition) and that determines the shear response; above critical state the particles must dilate during shear, below, a collapse behaviour is observed.

Soils which dilate during shear have their effective stress increase, this means they momentarily become stronger. Soils which collapse have the effective stress drop. When the effective stress becomes near zero the soil-water mixture can behave as a fluid.

Effective stress in soil mechanics is the total stress of the soil mass subtracted by the hydrostatic force exerted by water.

Soils do not liquefy instantaneously – liquefaction is a cyclic shear phenomena which requires strain, time, and cycles to develop.

For instance soils which are not considered liquefiable under a 1-in-475 year return period earthquake may liquefy during a 1-in-2475 earthquake. This is a result of the different energy released by the seismic event (ie. more strain cycles of greater magnitude).

The susceptibility to soils due to an earthquake is also a function of very localized differences in stratigraphy. Local soil conditions can attenuate or amplify seismic motions. The design near surface response spectra of a site in Richmond, B.C., will differ greatly from a site on Terminal Avenue in Vancouver, which will differ from a site a few hundred meters to the south on Broadway.

**

For those in Canada this site will allow you to determine the current National Building Code Seismic Design Criteria for your location: http://earthquakescanada.nrcan.gc.ca/hazard-alea/interpolat/index-eng.php
- apoxia
  
  GreyEminence
  
  Thanks for that, but I’m going to stick with what the geologist said regarding how fast liquefaction occurs.
  
  We have five or six times more liquefaction in this earthquake than the 7.1 back in September.
GreyEminence

Apoxia,

To reference USGS;
http://earthquake.usgs.gov/earthquakes/recenteqsww/Quakes/us2010atbj.php#details
http://earthquake.usgs.gov/earthquakes/eqinthenews/2011/usb0001igm/

The 7.0 magnitude quake had an interpolated epicentre distance of 45km and a depth of 5km.

The 6.3 magnitude quake had an interpolated epicentre distance of 6km and a depth of 5km.

Magnitude simply refers to the amount of energy released by the quake. Proximity to that release makes a big difference, the second quake was almost an order of magnitude less with respect to energy but the proximity to Christchurch would make it more intense by my estimation.

If you have a chance to ask any of the local geoscientists / geotechs ask about PGA (peak ground acceleration) and Arias intensity for the local monitoring stations.
Amelia_G

“Its strength is a function of its deformation,” like no-drip paint.
–Liquefaction explanation from my Geology 101 professor
travtastic

I might be mixing my science with my science, but does ground liquefaction bear any smiliarities to non-Newtonian fluids”?
Daemon

A rather large part of my own city is expected to have the same issue, as it was built on the silt of a river delta.
Kaleberg

My guess is that liquefaction takes place pretty quickly. After all, it explains why it a can with its upper end sealed penetrates sand more deeply than a can open at both ends for a given force. (It’s the opposite of what happens with water.) The air in the can with its upper end closed changes the structure of the sand allowing the can to sink in more deeply. (There was an article on this in Science recently: http://news.sciencemag.org/sciencenow/2011/02/convince-your-friends-youre-a-ge.html?ref=hp)
xzzy

This happened in Anchorage with their big earthquake in the 60′s.. near the airport, now known as ‘earthquake park.’

The whole area was covered with houses, and when the quake hit, the glacier silt that everyone was building on liquefied, sliding the whole mess into the ocean. If you visit earthquake park, you can see the occasional 2×4 poking out of the ground (or you could 20 years ago, it’s been a while since I was there).

Lots of stern warnings to never build there again were circulated, but if you look at the map now.. it is yet again a crowded neighborhood. I guess learning from mistakes is asking too much.
DrJ

xzzy

I’m fairly sure that the area you describe in Anchorage was damaged by landslides that were triggered by the earthquake, not liquifaction per se. Although, the physical processes that initiated the slides were probably similar to that described by GreyEminence.

http://earthquake.usgs.gov/earthquakes/states/events/1964_03_28.php
PKMousie

In Vermont, with it’s finely pulverized granite soils, there are many locations where you can jump up and down in a rhythm and the entire area will eventually start jiggling and wobbling like a waterbed.

It’s pretty cool!
- hadlock
  
  Your vermont story reminds of of Tesla’s Oscillator, where he accomplished the same thing in his neighborhood using just a 5lb piston.
  
  http://en.wikipedia.org/wiki/Tesla's_oscillator
magnetiquewolf

There is a strong correlation between earthquakes and crude oil extraction.

Oil floats on water. Mixed with other minerals (soil) it helps stabilize the first few layers of the earth’s surface. The more oil that is removed from the earth’s crust, the more unstable the crust is, the more earthquakes (and hurricanes) occur as a result.

Simple logic, folks.

You can’t take something from something and expect nothing.
- travtastic
  
  http://input-image.info/Physics-Troll.html
- flosofl
  
  Do you have any citations for that? I can maybe buy the earthquake thing, since I’m not sure about how the volume of oil removed, measures up against the volume of the crust. But hurricanes?
  
  I’m not being snarky. I’ve heard this before, but I’ve never seen any real studies or evidence.
  - travtastic
    
    I’m not sure about the oil stuff.
    
    Geothermal plants and liquid waste disposal cavities are known to trigger earthquakes by affecting the pressure and friction coefficients of geological formations (especially faults, and the disposal sites and power plants are generally located near them; they provide existing holes and near-surface mantle-heat). The same with dam construction, since it shifts entire lakes’ worth of weight from one place to another.
    
    The question is, is an oil reservoir of a sufficient magnitude (in volume or mass) to change local stress conditions? They seem huge to us, but I’m not sure how they stack up in comparison to other geological features. Another thing, oil deposits were laid down quite a long time ago. The rocks/ground they occupy are in constant motion, generally away from the seismically active areas.
    
    That being said, hurricanes are formed by heat, on the surface of the ocean. So, no.
    - travtastic
      
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  - penguinchris
    
    I’m a geologist; what that guy said is BS. On the surface to the layman it may sound rational, but if you’re familiar with the scale of this stuff and the actual structure of the crust it’s ridiculous. Not that e.g. hydro-fracking or drilling for geothermal can’t cause seismic activity… but not for any of the ridiculous reasons that guy says, and it’s generally not a dangerous threat.
    
    Geology, more than most other sciences, is plagued by people with no education or training in science (much less geology specifically) who come up with ridiculous “theories” and claim to be able to disprove what’s generally accepted. You can find this stuff all over the internet.
    
    I’ve personally had people describe their theories to me when they found out I was a geologist. I decided to smile and nod and walk away in most cases.
    
    Problem is when people who aren’t trained as geologists hear these ideas – they have no reason not to believe them, because most people also are not trained in critical or scientific thinking. I taught geology classes in Southern California (I’m not from there originally) and constantly had to correct the students’ misconceptions and outright ridiculous ideas about earthquakes and other aspects of geology.
    
    Also re: the guy talking about new construction on sand-fill islands near San Francisco: I guarantee they *do* understand the geology and the risks. Construction is extremely heavily regulated in California because of earthquake risk, and construction firms are not stupid. However, the real estate developers with the money don’t have to listen to the science, so long as they can sucker people into buying. Same deal in So Cal with construction in landslide-prone areas.