Earthquake Sounds Its Own Tsunami Warning

Earthquake Sounds Its Own Tsunami Warning
Date: 10 June 2013

Sound waves from big earthquakes such as Japan's could provide 15 to 20 minutes of advance notice before a tsunami hits

Along with seismic shaking, undersea earthquakes also produce low-frequency sound waves that travel through the ocean. The size of the sound signal is linked to the earthquake's magnitude.

"We've found that there's a strong correlation between the amplitude of the sound waves and the tsunami wave heights," co-author Eric Dunham, a Stanford geophysicist, said in a statement. "Sound waves propagate through water 10 times faster than the tsunami waves, so we can have knowledge of what's happening a hundred miles offshore within minutes of an earthquake occurring. We could know whether a tsunami is coming, how large it will be and when it will arrive."

The Japan Meteorological Agency issued a tsunami warning three minutes after the 2011 earthquake struck, but the agency underestimated the height of the waves. A revised warning of the bigger tsunami was sent out within minutes, but some residents did not hear or heed the new alert. In March, the country unveiled a new tsunami warning system with upgraded seismic sensors and offshore buoys to better track incoming waves.

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Foreshock of M 7.2 two days earlier and tsunami warning ..

2011-03-09 02:45:17.0 38.52 N 142.81 E 25 7.2 NEAR EAST COAST OF HONSHU, JAPAN

"A strong earthquake with a preliminary magnitude of 7.2 struck off the coast of northeast Japan on Wednesday, triggering a region-wide tsunami alert."

"There are no immediate reports of damage or injuries, as the tremor shook parts of northern Japan and Tokyo."

"The Japanese Meteorological Agency immediately issued a tsunami advisory of up to 20 inches."



Japan earthquake of M 9.0 on 3/11/2011, 15,883 deaths, 6,144 injured, 2,676 people missing

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