Comcast has made the Japanese NHK channel available for the next week. It can be accessed via channel 330 on Comcast. The broadcast is in Japanese, but if you have an SAP enabled TV or set top box, you can listen to a translation of the broadcast.
It took me a while to figure out how to enable secondary broadcast on my Comcast box, and I didn't find much info online, so I wanted to post it here in case anyone else was interested.
Using your remote, click the Menu Button, then go to:
Menu > Setup > Audio > Audio Setup > Default Audio Track
Set the Audio Track to "Espanol"
Right now, they are rotating between multiple languages (including English), and repeating tsunami warnings.
If you have info on how to access it for other Cable boxes, then post them in the comments.