It was the same day, I just don't know enough about the science to understand if this was a predicable event. Any theories out there?
The science is mightily disputed, especially by USGS employees, however the World Series quake and the Good Friday quake were full moon quakes. There is a folk knowledge in South America that full moons often precede volcano eruptions. There is assumed a three-day window since the moon doesn't suddenly become full but slowly moves into position. The Sumatra section of the faultline is released and won't pop again like that for a long time, but adjacent sections are as stressed as ever. 23 Jan, roughly, look for another quake of major size around the Ring of Fire, and maybe a significant volcano.