Earthquake Hazards
This sand was ejected to the surface by liquefaction during
the 2001 Seattle, Washington Earthquake. (Photo: David K. Norman, Washington DGER.)See your textbook for a full list. Here, I will expand on two earthquake hazards: liquefaction and tsunamis. Your textbook includes an entire chapter (Chapter 7) on tsunamis if you would like to know more.
Liquefaction
We discussed earlier how unconsolidated earth materials can amplify seismic waves. Now think more about this with the addition of water. I had said that the unconsolidated sediments turn into quicksand. Why does this happen? If you had a jar full of mud and you began to stir it or shake it vigorously, eventually, you would move the water molecules in between the sediment particles causing a break down in the sediment strength; in other words, you would negate any strength formed from frictional or cohesive forces of the particles. (Remember the soil engineering properties?)
This is what happens on large scales to unconsolidated sediments during an earthquake.
I want you to watch this short video on the effects of liquefaction in the recent earthquake in Christchurch, New Zealand. This was a M6.1 and occurred in February of 2011. This earthquake did not result in many casualties, but it is a valuable lesson for large cities which are built upon loose sediments like glacial till or fine-grained soils. (And, yes, I mean to say that this is a good lesson for Indianapolis.) Click here to go to the video.