The Richter Scale Details: Relative Earthquake Measures

The Richter Scale of Earthquake Measurement - magnitude scale of earthquakesAfter the devastating quake on Haiti on January 10/2010, and similar recent large magnitude quakes such as the Indian Ocean in 2004 which triggered a massive tsunami and the recent 2010 Chile quake (8.8 M), it is interesting to see how these events are measured, and what the relative meaning is for the numbers that we hear used (Magnitude, Impact). This posting presents the Richter Scale with its measures and examples.

*List o’ Largest Earthquakes link*

Richter Magnitude Test Scale: Named for Dr. Charles Francis Richter, and developed in 1935. For each whole number jump the impulse (shaking) increases 10-fold, but the energy increases 31.6227769 fold. As an example, an 8.7 magnitude quake generates an amplitude 890.2439024 times greater than a 5.8 quake, but releases an incredible 22,387.2113 times the energy.


Richter  Magnitude Approximate TNT equivalent Impulse Example
0.0 1 kg (2.2 lb) 0.1
0.5 5.62 kg (12.4 lb) .55 Large hand grenade
1.0 32 kg (70 lb) 1 (not felt) Construction site blast
1.5 177.83 kg (392 lb) 5.5 WWII conventional bombs
2.0 1 metric ton 10 (very minor, generally not felt) Late WWII conventional bombs
2.5 5.236 metric tons 55 WWII blockbuster bomb
3.0 31.62 metric tons 100 (minor, often felt) Massive Ordnance Air Blast bomb
3.5 177.83 metric tons 550 Chernobyl nuclear disaster, 1986
4.0 1 kiloton 1,000 (light, noticeable shaking) Small atomic bomb
4.5 5.62 kilotons 5,500
5.0 31.62 kilotons 10,ooo (moderate, moderate damage) Nagasaki atomic bomb (actual seismic yield was negligible since it detonated in the atmosphere); Lincolnshire earthquake (UK), 2008
5.4 125.89 kilotons 46,000 2008 Chino Hills earthquake (Los Angeles, United States)
5.5 17883 kilotons 55,000 Little Skull Mtn. earthquake (NV, USA), 1992; Alum Rock earthquake (CA, USA), 2007
6.0 1 megaton 100,000 (strong, destructive up to 100 miles) Double Spring Flat earthquake (NV, USA), 1994
6.5 5.62 megatons 550,000 Rhodes (Greece), 2008; Eureka Earthquake (Humboldt County CA, USA), 2010
6.7 11.22 megatons 730,000 Northridge earthquake (CA, USA), 1994
6.9 22.38 megatons 910,000 San Francisco Bay Area earthquake (CA, USA), 1989
7.0 31.62 megatons 1 MM (major, destructive up to a few 100 miles) Java earthquake (Indonesia), 2009; 12 January 2010 earthquake (Haiti)
7.1 44.67 megatons 1.9 MM Energy released is equivalent to that of Tsar Bomba, the largest thermonuclear weapon ever tested.
7.5 177.83 megatons 5.5 MM Kashmir earthquake (Pakistan), 2005; Antofagasta earthquake (Chile), 2007
7.8 501.12 megatons 8.2 MM Tangshan earthquake (China), 1976
8.0 1 gigaton 10 MM (great, destructive up to several 100 miles) Toba eruption 75,000 years ago; the largest known volcanic event; San Francisco earthquake (CA, USA), 1906; Queen Charlotte earthquake (BC, Canada), 1949; México City earthquake (Mexico), 1985; Gujarat earthquake (India), 2001; Chincha Alta earthquake (Peru), 2007; Sichuan earthquake (China), 2008 (initial estimate: 7.8)
8.5 5.62 gigatons 55 MM Sumatra earthquake (Indonesia), 2007

Vallenar, Chile November 10, 1922

9.0 31.62 gigatons 100MM (rare, destructive up top 1000′s of miles) off the coast of Kamchatka peninsula, Russia November 4, 1952
9.1 44.67 gigatons 190 MM Indian Ocean earthquake, 2004 (40 ZJ in this case
9.2 63.1 gigatons 280 MM Anchorage earthquake (AK, USA), 1964
9.5 177.823 gigatons 550 MM Valdivia earthquake (Chile), 1960
10.0 1 teraton 1 billion (inconceivable global impact) Never recorded
13 100 teratons 500 ZJ Yucatán Peninsula impact of asteroid hitting the earth (causing Chicxulub crater) 65 M yrs ago.
Source: Richard E.J. Driskill, Electromagnetic Spectrum Authority/ retired

Note that directly the Richter scale is not highly reliable for quakes under 2 or above 8.3 in size. The Richter scale is an open-ended scale. From magnitude 1 through 9, there are roughly 3,341,138 earthquakes each year  around the globe.

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  12. listmaster March 1, 2010 at 00:33

    LM stands corrected – sounds like this is an appreciated response from an expert. Thank you – thanks to your informative comment I believe the adjustments have just been made, and the data in the tables is corrected with your expertise cited as fact-checked reference/source :-)
    Cheers.

  13. Richard Driskill March 1, 2010 at 00:09

    Your list is ‘off’ because of erroneous mathematics-

    The actual energy (TNT equivalent) increases 31.6227769 fold for each whole division advance, not 32. As an example, 7.8 does not equal 600 MT but rather 501.1872336 Megatons, and 9.1 does not equal 67 GT but rather 44.6683592 Gigatons. In other words, don’t round off (which also means you can remove the word “Approximate” from the column heading) within your equations as error will be introduced.

    In a side note, ‘Little Boy’ (1,968′ AMSL over Hiroshima) was calculated at 16.1 kT, and ‘Fat man’ (1,650′ AMSL over Nagasaki) was calculated at 21.4 kT.

    If you got the ‘data’ from Wikipedia (as stated), once again this is another example why not to use it… it’s commonly wrong.

    If you can make the adjustments I’m sure your viewers would appreciate it.