Early this morning a massive magnitude 8.8 earthquake hit the coast region of Chile, South America, causing widespread damage to the area between Santiago and Concepcion, BioBio, Talca and other regions of Chile. Santiago is the capital and largest city in Chile. Concepcion is the second largest.
Located at 36.1° S by 72.6° W and at a preliminary depth estimate of 55 km, the quake burst generated tsunami warnings across the Pacific. Initial observed tsunami height above mean sea was reported to be approximately 8 feet ( 7.7 feet at Talcahuano, Chile (0653Z), 4.2 feet at Valparaiso, Chile (0708Z).
A tsunami is a wave front moving through the ocean (not on top of) at high speed (450km/hr), resulting from the lifting of a large mass of water by the earthquake. On the open ocean, it would be be barely perceptible, but when it approaches land, the depth of the pulse of wave energy causes it to crash into the rising sea floor, lifting and spilling the top of the wave forward on to the land as a surge of high flood water. Since a train of waves is usually created, the danger from a tsunami may exist for several hours as each wave in the train expends its energy on land, with the first wave not necessarily being the highest.
… A TSUNAMI IS A SERIES OF WAVES AND THE FIRST WAVE MAY NOT BE THE LARGEST. TSUNAMI WAVE HEIGHTS CANNOT BE PREDICTED AND CAN VARY SIGNIFICANTLY ALONG A COAST DUE TO LOCAL EFFECTS. THE TIME FROM ONE TSUNAMI WAVE TO THE NEXT CAN BE FIVE MINUTES TO AN HOUR, AND THE THREAT CAN CONTINUE FOR MANY HOURS AS MULTIPLE WAVES ARRIVE.
FOR ALL AREAS – WHEN NO MAJOR WAVES ARE OBSERVED FOR TWO HOURS AFTER THE ESTIMATED TIME OF ARRIVAL OR DAMAGING WAVES HAVE NOT OCCURRED FOR AT LEAST TWO HOURS THEN LOCAL AUTHORITIES CAN ASSUME THE THREAT IS PASSED. DANGER TO BOATS AND COASTAL STRUCTURES CAN CONTINUE FOR SEVERAL HOURS DUE TO RAPID CURRENTS. AS LOCAL CONDITIONS CAN CAUSE A WIDE VARIATION IN TSUNAMI WAVE ACTION THE ALL CLEAR DETERMINATION MUST BE MADE BY LOCAL AUTHORITIES.
ESTIMATED INITIAL TSUNAMI WAVE ARRIVAL TIMES AT FORECAST POINTS WITHIN THE WARNING AND WATCH AREAS ARE GIVEN BELOW. ACTUAL ARRIVAL TIMES MAY DIFFER AND THE INITIAL WAVE MAY NOT BE THE LARGEST. A TSUNAMI IS A SERIES OF WAVES AND THE TIME BETWEEN SUCCESSIVE WAVES CAN BE FIVE MINUTES TO ONE HOUR.
A TSUNAMI HAS BEEN GENERATED THAT COULD CAUSE DAMAGE ALONG COASTLINES OF ALL ISLANDS IN THE STATE OF HAWAII. URGENT ACTION SHOULD BE TAKEN TO PROTECT LIVES AND PROPERTY.
THE ESTIMATED ARRIVAL TIME IN HAWAII OF THE FIRST TSUNAMI WAVE IS 1119 AM HST SAT 27 FEB 2010 (Hawaii is 10 hours behind Eastern Standard Time).
Update: Hawai’i went into full disaster preparedness mode. They closed coastal roads, the US Navy moved ships out to sea from Pearl Harbour, as did many owners of small boats. The PTC anticipated that wave heights could be as high as 10 feet. All coastal areas of Hawaii were believed to be at risk. In the end, wave heights were less than a metre generally.
The two images below are screencaps at about 4:45ff HST of the draw down from the arrival of the first tsunami wave in Hilo Bay, Hawaii. The little beach on the left was flooded on the fill from the first wave. The second picture is a screencap of the fill from the first tsunami wave. As of this posting there have been 4 draws and fills.
This is the second tsunami warning issued in the past week. On February 23, 2010, a magnitude 7 earthquake struck the Ryukyu Islands in Japan, and on February 18, 2010, a deep magnitude 6.8 quake struck the China/Russian border on the Sea of Japan. Thus far, there have been more than 56 aftershocks greated than magnitude 5 in Chile.
While earthquakes are common around the Pacifc Rim, most have magnitude of 5 or less, and generally don’t cause significant damage or tsunamis.