After 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; Mxico 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 | Yucatn 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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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.
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.