Kelly Kiloton Index of Earthquake Moment Magnitudes 
The Richter Earthquake Magnitude Scale, which was perfected by Charles Richter of Cal Tech in 1935, has always been misleading for people who are not used to thinking logarithmically. In this case, it's log10: every whole position is 10 times greater than the one before. Therefore, if 4.0 is taken to be the equivalent of 10 units, 5.0 is 100.
But according to a new way of measuring earthquakes, based on the seismic "moment of force," translated to the equivalent energy released by an explosion of TNT, the Richter Scale is converted from a log10 to a 2/3 log10 scale. In this scale, every positional increase, e.g. Richter 4.0 to 5.0, goes up by a factor of 31.62, which we can round to 32. Thus, R 2.0 corresponds to the detonation of 1 ton of TNT, R 3.0 = 32t, R 4.0 = 1000t, R 5.0 = 32,000t, 6.0 = 1,000,000t, 7.0 = 32,000,000t, and so on. This "Moment Magnitude" is represented by M_{w}. The "w", introduced by Hiroo Kanamori in 1977, presumably stands for "work"; it refers to "elastic strain energy." The formula used here is: Tonnage = 10^{(1.5R3)}.
The Kelly Kiloton Index (KKI), formulated in 2006 by H. A. Kelly of UCLA, in consultation with Geoffrey Mess of the UCLA Math Department, aims at giving a "realistic" picture of earthquake energy. It uses the kiloton (= 1000 metric tons = 2,200,000 lbs) as the basic unit. Here is the KKI range for Richter 6.0 to 6.9 and for 7.0 to 7.9:
Richter

6.0

6.1

6.2

6.3

6.4

6.5

6.6

6.7

6.8

6.9

KKI

1000

1400

2000

2800

4000

5600

8000

11,000

16,000

22,000

Richter

7.0

7.1

7.2

7.3

7.4

7.5

7.6

7.7

7.8

7.9

KKI

32,000

45,000

63,000

90,000

125,000

180,000

250,000

355,000

500,000

710,000

The increase for every 2 positions, say, from R 6.0 to R 8.0, is not x 100, as it would be on a log10 scale, but x 1000. So, since 6.0 is 1000, 8.0 is KKI 1000 x 1000 = 1,000,000. Similarly, 8.1 is KKI 1400 x 1000 = 1,400,000, and so on. See below for a complete table.
Here is how some past earthquakes register on the Richter Scale and the Kelly Kiloton Index:
Assisi 1997
Northridge (LA) aftershock 1994
Sylmar (LA) 1971
Northridge (LA) 1994
Loma Prieta Peak (SF) 1989
Pakistan 2005
San Francisco 1906
Sumatra 2004
Chile 1960

Richter 5.6
Richter 5.9
Richter 6.6
Richter 6.7
Richter 7.1
Richter 7.6
Richter 8.3
Richter 9.2
Richter 9.5

KKI 250
KKI 710
KKI 8000
KKI 11,000
KKI 45,000
KKI 250,000
KKI 2,800,000
KKI 63,000,000
KKI 180,000,000

So, the Loma Prieta Earthquake (from San Francisco to Santa Cruz) of 1989 was more than 5 times bigger than the Sylmar quake of 1971, and 4 times bigger than the Northridge quake of 1994. But the San Francisco quake of 1906, just over one position larger on the Richter scale, was 62 times bigger than Loma Prieta, and the recent Sumatra quake of 2004, just two Richter positions higher, had 1400 times the energy. It should be clear that small quakes do not do much in the way of defusing or diffusing the pentup energy that the big ones have in store for us.
Complete Conversion Table
Richter Scale

Kelly Kiloton Index


2.0 2.5

.001 (1 ton) .0056 (5.6 tons)


3.0 3.5

.032 (32 tons) .180 (180 tons)


4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9

1 (1000 tons) 1.4 2 2.8 4 5.6 8 11 16 22


5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9

32 45 63 90 125 180 250 355 500 710

Assisi 1997
Northridge (LA) Aftershock 1994

6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9

10001400 2000 2800 4000 5600 8000 11,000 16,000 22,000

Sylmar (LA) 1971 Northridge (LA) 1994

7.0 7.17.2 7.3 7.4 7.5 7.6 7.7 7.8 7.9

32,000 45,00063,000 90,000 125,000180,000 250,000 355,000 500,000 710,000

Loma Prieta (SF) 1989
Pakistan 2005

8.0 8.18.2 8.3 8.4 8.5 8.6 8.7 8.8 8.9

1,000,000 1,400,0002,000,000 2,800,000 4,000,000 5,600,000 8,000,000 11,000,000 16,000,000 22,000,000

San Francisco 1906

9.0 9.1 9.29.3 9.4 9.5 9.6 9.7 9.8 9.9

32,000,000 45,000,000 63,000,000 90,000,000 125,000,000 180,000,000 250,000,000 355,000,000 500,000,000 710,000,000

Sumatra 2004
Chile 1960

10.0

1,000,000,000




