Christchurch, New Zealand

Source: PerthNow

As many of you have heard, there was an earthquake in Christchurch, New Zealand last month (February 21, 2011).  The magnitude of the earthquake was a 6.3, however it did more damage than expected for a 6.3 magnitude earthquake because because it was so shallow.  The earthquake occurred at only a 5 kilometer depth (3.1 miles).  USGS website.  The shallower the earthquake the more intense the damage will likely be.  The waves produced by the rupture of the earth have less of the earth to travel through and .  The earthquake did not last very long, however it caused a great amount of damage.

Ground liquefactions caused a significant amount of the damage that occurred as a result of this earthquake.  Ground liquefaction occurs in saturated soil.  The soil looses strength and stiffness as a result of excess stress caused by the earthquake.  This causes the soil to behave like a liquid and flow freely like quicksand.
The map below, shows where the earthquake was felt the most.  The red areas, had the highest intensity and saw the most damage.

Source: USGS

Those who are responsible for planning construction of buildings in the area did a poor job.  They did not expect to experience large magnitude earthquakes such as last month, and therefore did not plan accordingly.  Less damage would have been done if buildings were prepared for experiencing earthquakes.

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