Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.
By: Dr. Jeff Masters , 11:00 PM GMT em 11 de Março de 2011
A great earthquake rocked the coast of Japan at 5:46 GMT on March 11, generating a dangerous tsunami that raced across the Pacific. The mighty earthquake was rated 8.9 on the Richter scale, making it the 7th most powerful tremor in world history. The world's 8th largest earthquake, a magnitude 8.8 event, hit Chile on February 27, 2010; never before have two top-ten earthquakes hit so close together in time. Today's quake was the strongest in Japanese history, and will likely be the most expensive natural disaster in world history, surpassing the $133+ billion dollar price tag from Hurricane Katrina.
Figure 1. Model-computed energy from the March 11, 2011 tsunami as visualized by the NOAA Visualization Lab.
In the U.S., the highest tsunami waves from the earthquake hit northern California and southern Oregon, with a wave height of 8.1 feet observed at Crescent City, CA, 8.6 feet at Port San Luis, CA, 8.7 feet at Arena Cove, CA, and 6.1 feet at Port Orford, OR. The tsunami swept four photographers out to sea in the Crescent City harbor, injuring three of them and leaving one missing. Extensive damage was done to the harbor and 35 boats. Up to $2 million in damage also occurred in the Santa Cruz harbor south of San Francisco.
Figure 2. Tide gauge at Crescent City, CA during the March 11, 2011 tsunami. The green line shows the height of the tsunami wave; the red line shows the observed water level. The highest tsunami wave came at at 17 UTC (9am PST), an hour and 10 minutes after the initial wave, and was 7 feet high. Image credit: NOAA.
Crescent City was hit by a devastating tsunami after the March 28, 1964 magnitude 8.8 earthquake in Alaska, which killed ten people in the city and destroyed much of the business district. The city is fortunate today that the tsunami hit at low tide, or else water levels would have been five feet higher in the city during the wave. The tide gauge at Crescent City, CA (Figure 2) shows that at least 18 separate tsunami waves have hit the harbor as of 2:45pm PST. The first wave came at about 15:50 UTC (7:50am PST), was about 2.5 feet high, and was not preceded by the ocean falling and water being sucked out to sea. After this initial wave, the ocean level dropped rapidly by 8 feet, and then a series of large waves began rushing in and out, with up to a 13 foot difference between low water and high water. The rapid speed of the in-rushing and outflowing waves were what did the damage to the harbor and its boats. The largest wave came at 17 UTC (9am PST), an hour and 10 minutes after the initial wave, and was 8.1 feet high. Fortunately, this wave came near the time of low tide, and the wave was only 2 feet above last night's high tide mark. Tidal range between low and high tide is about 5 feet at Crescent City. The tide is now rising, and new tsunami waves with height of 3 - 4 feet are still rushing in and out, with the one just before 21 UTC (1pm PST) reaching a height about 2 feet above high tide.
Figure 3. Propagation of the March 11, 2011 Honshu tsunami was computed with the NOAA forecast method using the MOST model with the tsunami source inferred from DART® data. From the NOAA Center for Tsunami Research, located at NOAA PMEL in Seattle, WA.
Portlight.org is mobilizing to provide financial assistance to people with disabilities affected by the disaster, and there will undoubtedly be a huge relief effort by numerous charities in the wake of the earthquake. Your financial contributions and prayers for those affected will be valuable.
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