LogarithmicWe often say that earthquakes are logarithmic. On the moment magnitude earthquake scale,

LogarithmicWe often say that earthquakes are logarithmic. On the moment magnitude earthquake scale, a magnitude 9 earthquake is 10x as powerful as a magnitude 8 earthquake, and so forth. This simple graph makes that point very elegantly.This is a century of earthquake moments. The moment of an earthquake can be translated directly into energy, so this pie chart shows the energy released in earthquakes over a 100-year period.As you can see, almost all of the energy released in earthquakes happens in the largest quakes. 3 quakes make up nearly 50% of the seismic moment over an entire century, while every quake under magnitude 6 over an entire century is less than 10% of the total seismic energy released. This plot also specifically highlights the magnitude 7.8 San Francisco Earthquake from 1906 just to show how small a single quake that devastated a city can appear when compared to the really large quakes.One topic that came to my mind after seeing this plot is the idea of releasing seismic energy under control. It’s been known for decades that pumping water at pressure into fault zones can trigger earthquake swarms (more here: http://tmblr.co/Zyv2Js1nyyBP7). This concept has led to the idea that seismic energy could be released by pumping water into a fault zone and allowing small earthquakes to happen. However, the energy of large earthquakes is so vastly higher than the energy of small quakes that the number of triggered earthquakes it would take to actually release seismic energy seems implausible. Releasing the energy of a magnitude 7 or 8 earthquake would require an absolutely huge number of smaller earthquakes, with a much bigger chance of accidentally just setting off a major disaster. Notably, I can cite an assignment I filled out as an undergraduate where I suggested this as an explanation for behavior seen on a fault - and was not explained this property of earthquakes when I made that mistake.-JBBImage credit: Richard Asterhttp://bit.ly/1TqNrbL -- source link

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