If there is one sliver of silver lining from the Japan earthquake it's the increasing awareness of the United State's High Frequency Active Aural Program. You should do some research to investigate the secrecy and background of this technology as it opens up the possibility of artificially created earthquakes. I don't know if it was responsible in this case other than the timing which certainly deflected our attention on protest in the middle East and specifically the Day of Rage planned in the United States oil dealer Saudi Arabia.
There are many other explanations for the earthquake and those should be explored too though the latest readings from Clif High's Web Bot point towards a long and continued 'tearing' or tremors of the earth from an initial colossal earthquake reading and a possible follow up earthquake on the West Coast of the United States.
There's an excellent article evaluating all the permutations over at Wiki World Order which shows that at the least HAARP technology is possibly able to predict events of this type. Which is worth knowing. If time is limited take a quick look at the published HAARP readings below.
Update US Airforce Admit to using HAARP for weather modifications.