Everyone knows the basic mechanics of earthquakes and that they occur due to slippage of faults, at fault lines.
So it is well realized that earthquakes originate from the sudden movements of the earth's tectonic plates, close to the earth's surface, along zones of pre-existing weakness called faults.
As such, great earthquakes are associated with major faults (cracks) in the crust. When the faults are locked tightly together, the strain accumulates without producing earthquakes. When the faults relax, the rocks slip and shake the earth.Incredible as it is, there was NO fault at or near Christchurch, New Zealand, prior to the September 2010 massive 7.0 quake!!
Instead, it is widely reported that last year's huge quake actually "ripped a new fault line in the Earth's surface".