Is there any way to know there will be an earthquake in advance?
Yes. The earthquake early warning system operated by the Meteorological Agency provides advance warning of earthquakes.
According to the agency, the nationwide system is unique to Japan. But it only gives people seconds, not days, to prepare.
When an earthquake hits, two kinds of waves travel underground, first the P-waves and then the S-waves. When the agency detects P-waves, a warning is sent immediately, before the S-waves, which people actually feel, arrive.
People can receive the warnings on mobile phones operated by NTT DoCoMo Inc., Softbank Mobile Corp. and KDDI's au, or through TV or radio broadcasts.
But according to the Meteorological Agency, there is as little as only 10 seconds between the warning and when the tremors arrive. Close to the epicenter, the quake arrives faster than the warning.
The Meteorological Agency updates its technology to improve the system every time it encounters problems. For example, the system didn't function properly after the March 11 quake because big quakes occurred too frequently. The agency is now working on solving this issue, according to its Seismological and Volcanological Department.