A huge 8.9 earthquake has struck Japan. A really nasty tsunami already has hit Hawaii and is due to strike the Pacific Northwest U.S. any minute now, with California an hour behind. Incredible video is coming in:

This one is almost deceptively calm until you get near the one-minute mark, and then you want all those guys on the bridge to get off the bridge and out of there.

For perspective, here are the largest earthquakes on record per Wikipedia. This one would rank number 7 worldwide, counting all the earthquakes we've ever been able to document (and estimate the sizes of) in recorded history.

1. 1960 Chile 9.5
2. 1964 Alaska 9.2
3. 2004 Sumatra 9.2
4. 1952 Kamchatka 9.0
5. 1868 Chile 9.0
6. 1700 Canadian/U.S. border West Coast 9.0
7. 2011 Japan 8.9

Every 0.1 increase in the Richter scale means about a 1.3x increase in intensity. Every 1.0 increase means a 10x increase in intensity. The difference between an 8.9 earthquake and a 9.5 earthquake is 10 to the power of (9.5-8.9), or 10 to the 0.6 power, which is about 4x, if I'm doing it right. So this earthquake was about 1/4 as big as the biggest one we know about, ever. Worldwide, earthquakes from 4.0 to 5.0 are basically a dime a dozen. From 5.0 to 6.0, they happen more than 100 times a month. From 6.0 to 7.0, a little over ten a month. From 7.0 to 8.0, a little over one a month. We can expect one over 8.0 only about once a year, and you can see from the above chart that "greater than 8.9" means you're going back hundreds of years to find a good pool of equivalent events.

It does get worse. Going back 65 million years gets you the asteroid impact that may have finished off the dinosaurs, and 250 million years gets you the Permian extinction -- the beginning of the Dinosaur Age -- which may or may not have had something to do with a million years or so of Siberian volcanoes leaving basaltic flows miles deep over an area nearly as big as the continental United States. Whether the Permian extinction resulted in part from an impact, or seismic upheavals, or something else, no one knows for sure.

They say the tsunami in northern Japan was 33 feet. So far, though, the reports in Hawaii and the U.S. west coast sound pretty moderate. I hope so.

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