Slack
I hope that they remember to leave a big loop of slack cable at the Japanese end. Didn't Japan move a metre to the left during the last big earthquake?
Edit: I'm wrong, it moved 2.4m towards North America. That's ruined my image of the plug being pulled out of the wall in Los Angeles :(
https://en.wikipedia.org/wiki/2011_T%C5%8Dhoku_earthquake_and_tsunami#Geophysical_effects