new earthquake warning system

There seems to be a new earthquake warning system in place lately in Japan. It must have come into effect in these few days.

Here is how it works:
1) sizable earthquake happens somewhere in this area (Kanto regions)
2) a loud warning beeps and vibrants for a few seconds on your cellphone (despite silence setting)
3) impact expected 5 - 10 seconds from time of warning
4) brace

We had our first warning this afternoon at around 5pm. We were in class so I got the students ready to dodge under the table if/when it'd happen. But it didn't, turned out a fairly regional quake didn't make itself felt over here. Still, a bit of a scare. We thought it was "the Big One".