Square directly attributes the temporary closures to "continuous earthquakes occurring in the eastern regions of Japan," and says that servers will be down for "at least a week starting on Mar. 13, 2011 3:00 (PDT) [7:00 EST]." It is currently unknown when the servers will go back up, but Square promises regular updates as they come in. Neither game will charge subscription fees through April as a result.
If you'd like to help out, head over to the Red Cross site and donate what you can.