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 theRichter 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 (causingChicxulub 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.