Is this a variation in frequency outside the statistical normal distribution?
There has been a increase in the earthquakes that have happened lately.
Between the time of 26-FEB-2011 14:35:01 and 28-MAR-2011 14:45:00, there were 1201 earthquakes over magnitude 4, and 59 of them were over magnitude 6.
http://www.iris.edu/seismon/last30.html