ganbarou, is the same as in your sig
"Keep up your spirit"
Keep fighting
Don't give up!
You can do it!
Hang in there!
etc, etc
We don't have a literal translation for this word, so it depends on the context to find the closest English we can get to it.
This refers to the march 11th quake, the kanji after I dare say are place names which break all kanji rulles as to how it read...
Stay strong, Japan!
Don't give up, East Matsushima!
Keep going, Matsushima Base!
(Stay strong)
For March 11th 2011 and for the future.