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Seismic magnitude scales

Updated: 12/11/2025, 5:35:37 PM Wikipedia source

Seismic magnitude scales are used to describe the overall strength or "size" of an earthquake. These are distinguished from seismic intensity scales that categorize the intensity or severity of ground shaking (quaking) caused by an earthquake at a given location. Magnitudes are usually determined from measurements of an earthquake's seismic waves as recorded on a seismogram. Magnitude scales vary based on what aspect of the seismic waves are measured and how they are measured. Different magnitude scales are necessary because of differences in earthquakes, the information available, and the purposes for which the magnitudes are used.

Tables

06 July 1997
06 July 1997
Date
06 July 1997
ISC #
1035633
Lat.
−30.06
Long.
−71.87
Depth
23 km
Damage
Barely felt
Ms
6.5
Mw
6.9
mb
5.8
Me
6.1
Type of fault
interplate-thrust
15 Oct. 1997
15 Oct. 1997
Date
15 Oct. 1997
ISC #
1047434
Lat.
−30.93
Long.
−71.22
Depth
58 km
Damage
Extensive
Ms
6.8
Mw
7.1
mb
6.8
Me
7.5
Type of fault
intraslab-normal
Difference:
Difference:
Date
Difference:
Lat.
0.3
Long.
0.2
Depth
1.0
Damage
1.4
Date
ISC #
Lat.
Long.
Depth
Damage
Ms
Mw
mb
Me
Type of fault
06 July 1997
1035633
−30.06
−71.87
23 km
Barely felt
6.5
6.9
5.8
6.1
interplate-thrust
15 Oct. 1997
1047434
−30.93
−71.22
58 km
Extensive
6.8
7.1
6.8
7.5
intraslab-normal
Difference:
0.3
0.2
1.0
1.4

References

  1. Bormann, Wendt & Di Giacomo 2013, p. 37. The relationship between magnitude and the energy released is complicated. See
  2. Bormann, Wendt & Di Giacomo 2013, §3.1.2.1.
  3. Bolt 1993, p. 164 et seq..
  4. Bolt 1993, pp. 170–171.
  5. Bolt 1993, p. 170.
  6. See Bolt 1993, Chapters 2 and 3, for a very readable explanation of these waves and their interpretation. J. R. Kayal's
    https://escweb.wr.usgs.gov/share/mooney/SriL.II2.pdf
  7. See Havskov & Ottemöller 2009, §1.4, pp. 20–21, for a short explanation, or MNSOP-2 EX 3.1 2012 for a technical descript
  8. Chung & Bernreuter 1980, p. 1.
  9. Bormann, Wendt & Di Giacomo 2013, p. 18.
  10. IASPEI IS 3.3 2014, pp. 2–3.
  11. Kanamori 1983, p. 187.
  12. Richter 1935, p. 7.
  13. Spence, Sipkin & Choy 1989, p. 61.
  14. Richter 1935, pp. 5; Chung & Bernreuter 1980, p. 10. Subsequently redefined by Hutton & Boore 1987 as 10 mm of motion by
  15. Chung & Bernreuter 1980, p. 1; Kanamori 1983, p. 187, figure 2.
  16. Chung & Bernreuter 1980, p. ix.
  17. The "USGS Earthquake Magnitude Policy" for reporting earthquake magnitudes to the public as formulated by the USGS Earth
    https://earthquake.usgs.gov/aboutus/docs/020204mag_policy.php
  18. Bormann, Wendt & Di Giacomo 2013, §3.2.4, p. 59.
  19. Rautian & Leith 2002, pp. 158, 162.
  20. See Datasheet 3.1 in NMSOP-2 Archived 2019-08-04 at the Wayback Machine for a partial compilation and references.
    http://bib.telegrafenberg.de/publizieren/vertrieb/nmsop/
  21. Katsumata 1996; Bormann, Wendt & Di Giacomo 2013, §3.2.4.7, p. 78; Doi 2010.
  22. Bormann & Saul 2009, p. 2478.
  23. See also figure 3.70 in NMSOP-2.
  24. Havskov & Ottemöller 2009, p. 17.
  25. Bormann, Wendt & Di Giacomo 2013, p. 37; Havskov & Ottemöller 2009, §6.5. See also Abe 1981.
  26. Havskov & Ottemöller 2009, p. 191.
  27. Bormann & Saul 2009, p. 2482.
  28. MNSOP-2/IASPEI IS 3.3 2014, §4.2, pp. 15–16.
  29. Kanamori 1983, pp. 189, 196; Chung & Bernreuter 1980, p. 5.
  30. Bormann, Wendt & Di Giacomo 2013, pp. 37, 39; Bolt (1993, pp. 88–93) examines this at length.
  31. Bormann, Wendt & Di Giacomo 2013, p. 103.
  32. IASPEI IS 3.3 2014, p. 18.
  33. Nuttli 1983, p. 104; Bormann, Wendt & Di Giacomo 2013, p. 103.
  34. IASPEI/NMSOP-2 IS 3.2 2013, p. 8.
  35. Bormann, Wendt & Di Giacomo 2013, §3.2.4.4. The "g" subscript refers to the granitic layer through which Lg waves propag
    https://escweb.wr.usgs.gov/share/mooney/SriL.II2.pdf
  36. Nuttli 1973, p. 881.
  37. Bormann, Wendt & Di Giacomo 2013, §3.2.4.4.
  38. Havskov & Ottemöller 2009, pp. 17–19. See especially figure 1-10.
  39. Gutenberg 1945a; based on work by Gutenberg & Richter 1936.
  40. Gutenberg 1945a.
  41. Stover & Coffman 1993, p. 3.
  42. Bormann, Wendt & Di Giacomo 2013, pp. 81–84.
  43. MNSOP-2 DS 3.1 2012, p. 8.
  44. Bormann et al. 2007, p. 118.
  45. Rautian & Leith 2002, pp. 162, 164.
  46. Journal of Geophysical Research
    https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/JB084ib05p02348?casa_token=Ob3hlS8_Ur4AAAAA:V-crV2WsODI0_CZP662OUwD-t4uyd0-r3_RYD0dyHcjfF7S6OwvqVhY6GfdevVhtjmsqIERTz57y8cC7
  47. The IASPEI standard formula for deriving moment magnitude from seismic moment is Mw  = (2/3) (log M0  – 9.1). Formula 3.
  48. Anderson 2003, p. 944.
  49. Havskov & Ottemöller 2009, p. 198
  50. Havskov & Ottemöller 2009, p. 198; Bormann, Wendt & Di Giacomo 2013, p. 22.
  51. Bormann, Wendt & Di Giacomo 2013, p. 23
  52. NMSOP-2 IS 3.6 2012, §7.
  53. See Bormann, Wendt & Di Giacomo 2013, §3.2.7.2 for an extended discussion.
  54. NMSOP-2 IS 3.6 2012, §5.
  55. Bormann, Wendt & Di Giacomo 2013, p. 131.
  56. Rautian et al. 2007, p. 581.
  57. Rautian et al. 2007; NMSOP-2 IS 3.7 2012; Bormann, Wendt & Di Giacomo 2013, §3.2.4.6.
  58. Bindi et al. 2011, p. 330. Additional regression formulas for various regions can be found in Rautian et al. 2007, Table
  59. Rautian & Leith 2002, p. 164.
  60. Bormann, Wendt & Di Giacomo 2013, §3.2.6.7, p. 124.
  61. Abe 1979; Abe 1989, p. 28. More precisely, Mt  is based on far-field tsunami wave amplitudes in order to avoid some comp
  62. Blackford 1984, p. 29.
  63. Abe 1989, p. 28.
  64. Bormann, Wendt & Di Giacomo 2013, §3.2.8.5.
  65. Bormann, Wendt & Di Giacomo 2013, §3.2.4.5.
  66. Havskov & Ottemöller 2009, §6.3.
  67. Bormann, Wendt & Di Giacomo 2013, §3.2.4.5, pp. 71–72.
  68. Musson & Cecić 2012, p. 2.
  69. Gutenberg & Richter 1942.
  70. Grünthal 2011, p. 240.
  71. "Magnitude Types | U.S. Geological Survey"
    https://www.usgs.gov/programs/earthquake-hazards/magnitude-types
  72. Engdahl & Villaseñor 2002.
  73. Makris & Black 2004, p. 1032.
  74. Doi 2010.
  75. Hutton, Woessner & Haukson 2010, pp. 431, 433.
  76. NMSOP-2 IS 3.2 2013, pp. 1–2.
  77. Abe 1981, p. 74; Engdahl & Villaseñor 2002, p. 667.
  78. Engdahl & Villaseñor 2002, p. 688.
  79. Abe & Noguchi 1983.
  80. Abe 1981, p. 72.
  81. Defined as "a weighted mean between MB and MS". Gutenberg & Richter 1956, p. 1.
  82. "At Pasadena, a weighted mean is taken between mS as found directly from body waves, and mS, the corresponding value der
  83. E.g., Kanamori 1977.
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