It is interesting to observe that,major aftershocks at place where major quake has occurred ,is observed after 7 and half days and after 15 days (approximately). we have first major aftershock on 20/21st January 2010 at Haiti. By that sequence yet another major aftershock may occur on 28/29 th January 2010.
Time and again I have noticed this pattern.This is because,Moon plays a major role in triggering the earthquakes. After each 7 and half days Moon acquires next position exactly 90 degrees apart . Thus ,till the potent combinations is faded aftershocks continues,(in diminishing scale)