Fine-grained sediments can behave like toothpaste when strong seismic activity shakes the ground. The geologic term "liquefaction" describes the process by which consolidated, fine-grained soils that are saturated with water lose their cohesive strength. Increased water pressure, induced by lateral movement associated with seismic activity, removes the stress loading on the fine grains, allowing pore spaces to collapse and sediment grains to flow. With little to no support, buildings, civil structures and other infrastructures are left without stable ground to stand upon. The end result is catastrophic failure as pressurized soils behave like viscous liquids.
Perhaps the best example of catastrophic failure associated with this phenomenon is the 1964 earthquake in Niigata, Japan. This earthquake, with a magnitude of 7.5 on the Richter scale, caused buildings to tilt beyond the angle of the leaning tower of Pisa. The area was devastated, as bridges collapsed and other bearing structures failed as they sunk into the ground and lost their orientation.
Modern scientific and laboratory experiments have allowed us to entertain hopes that we can prevent future incidents. Some lab experiments use cement and soil mixtures while the science of sedimentology is practiced to carefully identify soils. Hopefully, we can stabilize the ground under existing structures and prevent contractors from developing on poor sediments.
Resources:
http://geomaps.wr.usgs.gov/sfgeo/liquefaction/image_pages/niigata_apts_bw.html
http://www.ce.washington.edu/~liquefaction/html/main.html
http://en.wikipedia.org/wiki/Soil_liquefaction
http://www.es.ucsc.edu/~es10/fieldtripEarthQ/Damage1.html
Image Credit: Wikipedia
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Re: Liquefaction Hits Japan
