Richter Scale

The Richter scale is based on measurement of seismic waves, used to determine the magnitude of an earthquake at its epicenter. The magnitude of an earthquake differs from its intensity, measured by the Mercalli scale, which is subjective and varies from place to place for the same earthquake. The Richter scale was named for U.S. seismologist Charles Richter (1900–1985).

Magnitude

Relative amount of energy released

Examples

1	1
2	31
3	960
4	30,000	1979, Carlisle, England (4.7)
5	920,000	1990, Wrexham, Wales (5.1)
6	29,000,000	1971, San Fernando, CA (6.5)
		1988, northern Armenia (6.8)
7	890,000,000	1989, Loma Prieta, CA (7.1)
		1995, Kobe, Japan (7.2)
		1999, Izmit, Turkey (7.4)
		1999, Taiwan (7.6)
		1990, Rasht, Iran (7.7)
		1906, San Francisco, CA (7.7-7.9)*
8	28,000,000,000	1976, Tangshan, China (8.0)
		1920, Gansu, China (8.6)
		1755, Lisbon, Portugal (8.7)
9	850,000,000,000	1964, Prince William Sound, AK (9.2)
*Richter's original estimate of a magnitude of 8.3 has been revised by two recent studies carried out by the California Institute of Technology and the U.S. Geological Survey.

Source: U.S. Geological Survey.

Appears in these articles:

San Francisco Earthquake and Fire; Earthquake

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