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It’s Kelly versus Richter, or earthquakes for dummies


The Richter Scale was developed by Charles Richter of the California Institute of Technology in 1935. A lot of people know that as the numbers go higher on this scale, they represent earthquakes of more severity than one would think from just looking at the bare figures. Some people even know that because the scale is logarithmic, the quakes are a hell of a lot worse because everything goes up exponentially � in the technical, not common, meaning of the term.

But a lot of people don’t know any of this. They think that the numbers speak for themselves, like ordinary numbers. So I decided to come up with a scale that tells the layperson precisely how bad things really are. (My numerate friends scoffed at the idea, saying that everyone knows what logarithms do. Well, it was all vague to me until I brushed up on my high school math.)

The proposed Kelly Scale advanced by 10s. I started with Richter 3.0, which is good enough because quakes less than 3.5 are usually not felt. That means Richter 4.0 would be 10, Richter 5.0 100, Richter 7.0 10,000 and Richter 10.0 a whopping 1 million.

But then my lunchtime consultant, Geoffrey Mess, associate professor of mathematics, warned me to hold my horses. On looking into the matter, he suggested that I do a more useful scale based on the amount of energy released at the “moment of force,” which increases not by a factor of 10 but of 32. Thus, R 2.0 corresponds to the detonation of 1 metric ton of TNT, 3.0 to 32 tons, 4.0 to 1,000 tons, and so on.

So let’s set up a “realistic” TNT range, calling it the Kelly Kiloton Index (KKI), since we’ll use the kilo-ton (1,000 tons equals 2,200,000 pounds) as the basic unit.

Table I shows the KKI range for Richter 6.0 to 6.5 and for 7.0 to 7.5.

For a complete table, see my Web site:

Table II shows how some past earthquakes register on the Richter Scale and on the KKI.

Sobering, isn’t it, to think that the 1989 Loma Prieta Earthquake (from San Francisco to Santa Cruz) was more than five times bigger than the 1971 Sylmar quake, and four times bigger than the Northridge quake of 1994?

UCLA earthquake specialist Dave Jackson tells me that because the main function of earthquakes is to release pent-up stress energy, small ones don’t significantly “release the stress,” as many people believe. I hope you agree with me that the Kelly Kiloton Index brings these lessons home more graphically than Richter’s numbers.

Kelly is professor emeritus of English.

TableI Richter KKI 6.0 1000 6.1 1400 6.2 2000 6.3 2800 6.4 4000 6.5 5600 TableII Richter KKI Assisi 1997 5.6 250 Northridge (LA) aftershock 1994 5.9 710 Sylmar (LA) 1971 6.6 8000 Northridge (LA) 1994 6.7 11,000 Loma Prieta Peak (SF) 1989 7.1 45,000 Pakistan 2005 7.6 250,000 San Francisco 1906 8.3 2,800,000 Sumatra 2004 9.2 63,000,000 Chile 1960 9.5 180,000,000

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