POWER OUTAGE IN TOKYO

I woke up feeling too hot this morning. The air-conditioner had been stopped though I left it on last night. When I went to a rest room the light wasn't on. I also checked if the breakers have tripped, it looked right. Then, I opened the door and looked at the light of the elevator, I found the light off. My apartment lost power. Why? How large area was knocked out power? These days, I hardly listen to radio so I didn't come up with the idea that I could get some informations from a radio. After all, I had to wait to recover power to get information from TV. If a terrorist attack or a big earthquake hit Tokyo, we will get panickey. We can't do anything without power now. It is very frightening to think the cases.