Because the Pacific Plate is moving to the northwest, and Japan, New Zealand, Alaska, and California are all located on the boundary of that plate. Haiti and Chili are on the boundaries of other plates, and when one moves, it effects the one next to it. My bet is on Anchorage Alaska for the next big quake.
Another Answer:
It's because on plate banged into another one which made it go down and then it flicked up causing an earthquake and a tsunami.
A tsunami hit japan after the earthquake.
In Japan
The 8.9 Japan Earthquake
earthquake in ocean
Friday
East of Sendai
In march 2011
Tectonic plates shifted, creating the earthquake.
The epicenter of the earthquake was offshore, close to Sendai, Japan.
The plates moved so this can occur the earthquake.
Before you were born
The Northeastern Coast.