Earthquake in Japan

Since last night there has been a few earthquakes in Japan. This afternoon as I was watching TV suddenly an alarm appeared on the screen, warning me of a big earthquake coming. A few seconds later the house started to shake. It lasted for about 15 to 20 seconds. Then a Tsunami warning also appeared on the  screen.
It was the first time I saw an alarm like this . It is a new earthquake warning system in Japan. That is so great. It did not give me much time to prepare myrself  but my mind was ready. This earthquake was of a M 6.8 but there was no damages anywhere.......  my family did not panicked, they stayed calm......... well trained !!!