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Template:M

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  • For the "small letter m with dot below" please use the HTML encoding "&7747;", or the Unicode "1E43" code.

Given a valid code (see table), outputs an earthquake magnitude scale label, either the generic M, or a subtype (such as Mw or mbLg), conformable with the labels most commonly used by the major seismological authorities. The article is automatically added to a tracking category. Optionally adds a value or relation, identifies a source, or links to explanatory text at Seismic magnitude scales.

Usage

  • {{ M | <code*> | <value or relation> | src = <source> | link=y }}

A valid code is required (see table), other parameters are optional.

Examples

Label only:

  • {{M|w}} → Mw

With a value or range:

  • {{M|s|5.1}} → Ms  5.1.
  • {{M|w|6.2 – 6.5}} → Mw  6.2 – 6.5

Label wikilinked to explanatory text (useful for first mention):

  • {{M|t|link=y}} → Mt
  • {{M|b|5.2|link=y}} → mb  5.2

To show that a magnitude is from a particular catalog or source use |src=:

  • {{M|w|8.1|src=HRV}}, {{M|e|8.8|src=USGS-PDE}} → Mw (HRV)  8.1,   Me (USGS-PDE)  8.8
(Note: this is not suitable for purposes of WP:Verification.)

There are multiple magnitude scales. To maintain accuracy and avoid error please use the proper code (see below). If you are uncertain use the special maintenance code "?", which flags this instance for further attention:

  • {{M|?}} → M

Typical use in article text, with in-line citation:

  • The 1964 Alaska earthquake, magnitude {{M|w|6.7|src=NEIC}}<ref>{{short-isc|EHB|869809}}.</ref> ....

The special code "magnitude" produces a suitable wikilink for generic use:

The special codes "M" and "mag" produce a suitably wikilinked caption for use in tables:

  • {{M|M}} → M; {{M|mag}} → Mag.

 Important note: Please do NOT specify a magnitude as "Richter scale" just because a newspaper or other popular media says "Richter". That is usually incorrect. Earthquake magnitudes reported by the U.S. Geological Survey (USGS) and other seismological authorities now generally use the moment magnitude scale for magnitudes greater than 4.0. While most newspapers and other popular media refer to this as the "Richter" magnitude, that is not correct. Richter's original scale, explicitly denoted with the symbol "ML" or "ML" (where "L" indicates "Local"), was developed for measuring the magnitude of earthquakes in the vicinity of southern California. While the "Richter" and moment magnitude scales are similar, they do differ, particularly for larger earthquakes.

In general: where any source specifies magnitude on a scale other than "Richter", or uses "M" (or "m") with one or more other letters (such as ML, Mw, Ms, or mb), that can be relied on; use the table below to match the label and determine the proper code.

Where a newspaper or other popular media refers to the scale or magnitude of a recent earthquake as "Richter" it is probably the popular mis-identification of the moment magnitude scale. Best practice is to check with an authoritative source, such as the USGS or the International Seismic Centre (see below). USGS policy is that magnitudes in press releases, indicated as "M" without any additional characters, are implicitly moment magnitude. But: do not use the "w" code if the source does not actually say "Mw" or "moment magnitude scale". If you have a strong basis for believing moment magnitude is meant – e.g., because it is a USGS press release – use the "dot" code to indicate an implicit Mw. E.g.: {{M|.|5.7}}→ M  5.7; {{M|.|link=}}M.

If you are not sure of the scale, use {{M|?}}.

Data sources

Newspapers and other mass media are not reliable sources for earthquake magnitudes. It is preferable that earthquake magnitudes always be obtained from authoritative sources, such as the following.

  • The ANSS (Advanced National Seismic System) Composite Catalog, commonly known as "ComCat" is a near-realtime repository of earthquake information from the USGS (United States Geological Survey) and various regional data centers, with additional data from seismic networks around the world. Event pages for significant events generally have an executive summary, a tectonic overview, past earthquake history of that area, ShakeMaps, and other material. ComCat can be accessed in several ways:
  • Latest Earthquakes. In most cases there is an initial report within 10 to 30 minutes of all magnitude 5.0+ earthquakes globally, and magnitude 4.0+ earthquakes within the contiguous U.S. Note that the magnitudes and locations in the initial reports are only first-order approximations, which get revised in the following hours, days, and months.
  • Significant Earthquakes archive: a chronological listing of events since 1900.
  • Interactive search.
All of these access methods link to event pages in the ANSS/ComCat catalog, which can be cited using {{short-anss}} and {{cite_anss}}.
  • The On-Line Bulletin (IRIS mirror) incorporates several catalogs (databases). There are catalog-specific search functions for finding events constrained by date period, magnitude range, or region (by latitude and longitude, or Flinn-Engdahl regions). Data may be revised years later as more data is obtained or processes refined. This is the most complete, most authoritative, and preferred source for earthquake magnitudes and epicenters.
  • Event Bibliography (IRIS mirror) of scientific articles for notable events, indexed chronologically. (Useful for finding ISC event id.)
  • The ISC-GEM Global Instrumental Earthquake Catalogue: Definitive magnitudes for selected earthquakes since 1900. (Source id: GEM.)
Data from the ISC can cited using {{short-isc}} and {{cite isc}}.

Earthquake magnitudes are given on different scales because they measure different aspects of the event. Estimates of magnitude may differ between networks and across time because of differences or changes in how the seismograms are read and the data processed. For details see the NMSOP-2 documentation (below).

Table of codes

These are the most commonly found scales of earthquake magnitude. Any scale not found in this table is mostly likely one of the following:

  • An intensity scale. See Seismic intensity scales for explanation. This template does not cover intensity scales.
  • A regional (or "local") scale used by some particular seismic network (or country). In general it is preferable to use one of the better known scales from the table. Exceptions are for historical reports; you will need to explicitly format as appropriate. If the scale has been properly calibrated (see MNSOP-2, Chapter 3, §3.2.4.3, p. 65) then "L" may be appropriate, along with the |src= parameter.
  • A technical scale. While these might come up in an article related to seismology, they are not appropriate for general description of earthquakes. If needed, please format appropriately. On first use be sure to add a footnote explaining the scale.

Be careful to distinguish upper- and lower-case "M/m", "B/b", "L/l", and "I/i". Other than that case is generally not significant, nor italicization or subscripting.

The following examples are representative, even comprehensive, but not complete.

Labels and codes for various earthquake magnitude scales
As seen in sources WP Code Mag. scale Cat. # Comments
IASPEI NMSOP USGS ISC BSSA
-- -- -- -- -- M ? Unspecified M_? 21 WP: scale is unspecified or indeterminate.
-- -- -- -- -- M ?? Needs verification M_?? 0 WP: the scale and/or magnitude needs verification.
-- -- -- -- -- M R? Dubious "Richter" M_R? 7 WP: "Richter" scale is asserted, but dubious.
UK Muk uk Unknown M_uk 7 Source says "unknown" scale. Might be 1954 MGR mag. See here.
ML Ml ML ML ML ML l Local ("Richter") M_L 69 §4.1 "Local" to Southern Calif. Adapted for other regions, but not necessarily comparable.
MJMA Mj MJMA MJMA jma JMA "Local" mag. M_jma 7 §3.2.4.7 Japanese Meteorological Agency. Also MJ, but not Mw(JMA).
M0 M0 0 seismic moment M_0 2 "M zero". A physical value, basis of Mw. In Newton-meters or dyne-centimeters
M M M . moment mag. M_w. 4 dot: implicit Mw.
Mw Mw Mw Mw w moment mag. M_w 706 §4.7 Generally preferred when available. Use only if "w" is present.
Mwb Mwb wb M_wb 3 Mw calculated from body-waves
Mwc Mwc wc M_wc 7 Mw from centroid moment
Mww Mww ww M_ww 7 Mw from W-phase centroid
Mwr Mwr wr M_wr 1 Mw at regional distance
Mwp Mwp wp M_wp 0 Mw from broadband P-waves §3.2.8.2
Mwpd Mwpd wpd M_wpd 1 Mwp w/ duration §3.2.8.3
Mi Mi i M_i 0 Only if lower-case "i"! USGS synonym for Mwp?
mb mb mb Mb mb mb b body-wave, short-period M_b 32 §4.3 Case sensitive: use "b"
mB mB -- M Mb(BB) mB B body-wave, broadband M_B 1 §4.2 Case sensitive: use "B"
mB_BB mB -- M Mb(BB) mBBB bbb body-wave, broadband M_Bbb 1 §4.2
mb_Lg mbLg mb_Lg, MLg mb(Lg) mbLg blg mb from Lg wave M_bLg 2 §3.2.4.4; §4.6 North America east of the Rocky Mountains, and other cratons
Mn MN mN n Nuttli (1973) M_N 1 §3.2.4.4; §4.6 Same as mbLg
mBc mBc bc Cumulative body-wave M_Bc 1 §3.2.8.1
MS Ms s surface wave M_s 199 §4.4 Generic
Ms_20 Ms Ms Ms Ms(20) Ms20 s20 surface-wave 20s M_s20 0 §4.4 Short period (20 sec.) surface waves
Ms_BB Ms -- Ms Ms(BB) MsBB sbb broadband surface wave M_sbb 0 §4.5
Mz z surface wave, vertical M_z 0 Used before measuring the vertical phase became standard.
MS7 Ms7 s7 surface wave M_s7 1 On Chinese seismograph
MSn Msn sn surface wave M_sn 0 1-second period per Nuttli (1983)
MGR MGR MGR gr Gutenberg-Richter M_gr 2 1954 G-R version of Ms. Includes MPAS ("Pasadena")
MR MR r Rothe M_r 0 Not "Richter"! Ms per Rothe 1969
MLH MLH lh Russian Ms M_LH 0 Parts of Russia (Obninsk)
Mc Mc Mc c coda length M_c 0 §3.2.4.5
Md MD MD Md d duration M_d 1 §3.2.4.5 Many variants. Not JMA displacement mag.
Mt t tsunami mag. M_t 1 §3.2.6.7 Used by PTWC
Mm Mm m mantle mag. M_m 0 §3.2.8.5 Used by PTWC
Me e energy mag. M_e 3 §3.2.7.2
K K-class K 0 See Energy class. Use Template:K
M(K) M(K) k K-class mag. M_K 0 Mag. calculated from "energy class" K
Mms ms macroseismic M_ms 0 §3.2.6.6 Generic mag. estimated from macroseismic effects
FA Mfa Mfa fa mb from felt-area M_fa 13 Est. from extent of felt-area. Multiple methods.
MLa Mla la ML from felt-area M_la 7 ML est. from intensity reports; for Calif. and Hawaii
MI MI I ML from intensity M_I 2 Only if upper-case "I"! Est. from epicentral intensity.

Examples of use are from the International Association of Earth Physics and Interior (IASPEI), the first edition of the New Manual of Seismological Practice (NMSOP)(the second edition follows the IASPEI), the United States Geological Survey (USGS) National Earthquake Information Center (NEIC), the International Seismological Centre (ISC), and the Bulletin of the Seismological Society of America (BSSA), as summarized in table 3 of the IASPEI/MNSOP-2 Information Sheet 3.3. Additional magnitude scales from Chapter 3 of MNSOP-2, ISC documentation, the USGS, and a review of the literature. Section numbers under "Comments" are for either Chapter 3, or Information Sheet 3.3

The nomenclature style implemented here is adapted from IASPEI/MNSOP-2 Information Sheet 3.3. This style differs from IASPEI style mainly in using subscripts rather than underscores, and from BSSA style mainly in not using parentheses.

"Cat.": the Categories for tracking use of these various scales. "#" is the number of pages in that category (when last checked).

Principal references on usage are:

  • Bormann, P., ed. (2012), New Manual of Seismological Observatory Practice 2 (NMSOP-2), Potsdam: IASPEI/GFZ German Research Centre for Geosciences, doi:10.2312/GFZ.NMSOP-2.
  • Bormann, P.; Dewey, J. W. (2014), "Information Sheet 3.3: The new IASPEI standards for determining magnitudes from digital data and their relation to classical magnitudes." (PDF), in Bormann, New Manual of Seismological Observatory Practice 2 (NMSOP-2), doi:10.2312/GFZ.NMSOP-2_IS_3.3.

These sources also have extensive discussion and references on the derivation and comparison of the various scales.

See also

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