As long as we’re on the topic of things I don’t understand…
In light of the earthquake off the coast of Japan, I took a look at the list of most powerful earthquakes ever recorded. And I guess it’s small sample size, but I find it striking that 3 of the 8 most powerful have occurred in the last 7 years (and 6 of the 8 are in the last 60 years).
It might just be random, but I wonder if there are periods in history when powerful earthquakes are more common worldwide.
Also, it’s worth keeping in mind that the Richter scale rating does not correlate all that well with how deadly a quake will end up being. That has more to do with population centers and engineering. Notably absent from the most powerful earthquake lists are some of the most destructive ones such as the 7.0 2010 Haiti quake, the 7.6 one in Pakistan in 2005, and the 8.0 one in the Sichuan region of China in 2008.