2011 Sendai Earthquake And Tsunami, Tōhoku Region, Pacific Ocean

The estimates of the Sendai earthquake's magnitude made it the most powerful earthquake to hit Japan and one of the five most powerful earthquakes in the world overall since modern record-keeping began in 1900. Japanese Prime Minister Naoto Kan stated during a press conference that "in the 65 years after the end of World War II, this is the toughest and the most difficult crisis for Japan."
Earthquake
The main earthquake was preceded by a number of large foreshocks, beginning with a 7.2 MW event on 9 March approximately 40 km (25 mi) from 11 March quake, and followed by another three on the same day in excess of 6 MW in magnitude. One minute prior to the effects of the earthquake being felt in Tokyo, the Earthquake Early Warning system connected to more than 1,000 seismometers in Japan sent out warnings on television of an impending earthquake to millions. This was possible because the damaging seismic S-waves, traveling at 4 kilometers per second, took about 90 seconds to travel the 373 km to Tokyo. The early warning is believed by the Japan Meteorological Agency to have saved many lives.