Experts say Japan's tsunami warning system won a seemingly impossible race against giant ocean waves, offering possible lessons to countries like India.
The Japan Meteorological Agency put out its first tsunami warning with details of which prefectures were likely to face the most dangerous waves, at 2.49pm just three minutes after the quake on March 11.
A detailed warning, listing the height of waves likely to strike each prefecture and the time of arrival of the tsunami at each place followed a minute later - at 2.50pm.
The warnings were too late for Iwate prefecture, where the tsunami stuck first at 2:49pm, but beat the waves to all other prefectures.
"...This is the best timing I have seen for a tsunami warning system, and is an example for all of us," Sri Lankan tsunami expert Rohan Samarajiva said.
Japan's timing is significant for countries such as India and Sri Lanka because the nearest fault-line in the Indian Ocean lies near the Andaman and Nicobar Islands.
While Japan is forced to face tsunamis - generated just off its coast - India has up to 120 minutes before a tele-tsunami (long-distance tsunami) hits the Tamil Nadu coast.
Reducing the time needed for issuing warnings increases the time available for evacuations, experts said. Indonesia took 14 minutes to issue warnings about the 2004 tsunami off Sumatra.
The Indian National Centre for Ocean Information Services took eight minutes to put out its first bulletin on the Japan quake last Friday. The key to the Japanese success appears to lie in pre-analysed models that allowed a fully-automated warning system to make near-immediate announcements, the experts said.
"India's tsunami warning system is now much better than it was in 2004. But there are things to learn from the Japanese..." IIT Kharagpur professor PK Bhaskaran said.
The process of warnings involves sensors on the ocean bed picking up wave signals, transmitting them to land stations, evaluating the wave height and time before the tsunami hits land, and obtaining clearances for evacuation.