Template:Earthquake magnitude

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{{M}}

For the "small letter m with dot below" please copy-and-paste: ṃ

Given a valid code (see table), outputs an earthquake magnitude scale label, either the generic M, or a subtype (such as M_w  or mb_Lg ), 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

The full name serves to better identify this template's purpose. For most practical purposes, the shortcut {{M}} is used as described below.

{{ 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}} → M_w

With a value or range:

{{M|s|5.1}} → M_s 5.1.
{{M|w|6.2 – 6.5}} → M_w 6.2 – 6.5

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

{{M|t|link=y}} → M_t
{{M|b|5.2|link=y}} → mb5.2

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}} → M_w ^(HRV) 8.1, M_e ^(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:

A magnitude 7 earthquake ....

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

{{M|M}} → M; {{M|mag}} → Mag.

The standard symbol for seismic moment can be produced as straight text, or as a math variable (applies CSS 'texhtml' styling using {{mvar}}):

{{M|0}} → M₀ ; {{M|0tex}} → $M 0$

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 "M_L" (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 earthquakes stronger than about M 6.5, or deeper than about 50 km.

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 "M_w" 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 M_w. E.g.: {{M|.|5.7}}→ M5.7; {{M|.|link=y}}→ M.

If you are not sure of the scale, use {{M|?}}. See below on how to find authoritative magnitudes.

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 Comprehensive Catalog (ComCat), which can be cited using {{short-anss}} and {{cite_anss}}.

The ISC (International Seismological Centre) is the final and authoritative archive of global earthquake data. Services include:

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, or are measured in different ways. It is valid to list multiple magnitudes for an event (not to be confused with multiple events such as foreshocks, aftershocks, and doublet earthquakes). 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 examples in the table 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		WP	Code	Mag. scale	Cat.	#	Comments
--	--	--	--	--		M	?	Unspecified	M_?	0	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?	0	WP: "Richter" scale is asserted, but dubious.

		UK			→	M_uk	uk	Unknown	M_uk	0	Source says "unknown" scale. Might be 1954 M_GR or M_PAS mag.; see below (gr), or here.
ML	M`l`	ML	M_L	M_L	→	M_L	`l`	Local ("Richter")	M_L	0	§4.1. "Local" to Southern Calif. Adapted for other regions, but not necessarily comparable.
	M_JMA	Mj		M_JMA	→	M_JMA	jma	JMA "Local" mag.	M_jma	0	§3.2.4.7. Japanese Meteorological Agency. Also M_J or MJMA, but not M_w(JMA).
		Mh		M_h	→	M_h	h	by "hand"	M_h	0	Ad hoc methods for special cases

M₀, M₀	M₀	M₀			→	M₀	0	seismic moment	M_0	0	"M zero". A physical value, basis of M_w. In Newton-meters or dyne-centimeters
				$M 0$	→	$M 0$	0tex	seismic moment	M_0tex	0	"M zero" as a math variable in text
		M		M	→	M	.	moment mag.	M_w.	0	dot: implicit Mw.
Mw		Mw, w		Mw	→	M_w	w	moment mag.	M_w	0	§4.7. Use only for explicit M_w, Mw, or mw.
		Mww, ww			→	M_ww	ww		M_ww	0	M_w from centroid m.t.i. (moment tensor inversion) of W-phase.
		Mwc, wc			→	M_wc	wc		M_wc	0	M_w from centroid m.t.i. of long-period surface waves.
		Mwb, wb			→	M_wb	wb		M_wb	0	M_w from m.t.i. of long-period body waves.
		Mwr, wr			→	M_wr	wr		M_wr	0	M_w from m.t.i. of whole seismogram at regional distances.
		Mwp, wp			→	M_wp	wp		M_wp	0	M_w from integrated p-wave §3.2.8.2
Mwpd					→	M_wpd	wpd		M_wpd	0	M_wp w/ duration §3.2.8.3
		M_i			→	M_i	`i`		M_i	0	Only if lower-case "`i`"! USGS synonym for Mwp

mb	mb	mb	Mb	m_b	→	mb	b	body-wave, short-period	M_b	0	§4.3. Case sensitive: use "b"
mB	mB	--	M	M_b(BB)	→	mB	B	body-wave, broadband	M_B	0	§4.2; Gutenberg, 1945b,c. Case sensitive: use "B".
mB_BB	mB	--	M	M_b(BB)	→	mB_BB	bbb	body-wave, broadband	M_Bbb	0	§4.2
mb_Lg	mbLg	mb_Lg, MLg		m_b(L_g)	→	mb_Lg	b`l`g	mb from Lg wave	M_bLg	0	§3.2.4.4; §4.6; Nuttli, 1986. North America east of the Rocky Mountains, and other cratons
		Mn	MN		→	m_N	n	mb from Lg wave	M_N	0	§3.2.4.4; §4.6; Nuttli, 1973. Same as mb_Lg
mBc					→	mB_c	bc	Cumulative body-wave	M_Bc	0	§3.2.8.1

		Ms	Ms	M_s	→	M_s	s	surface wave	M_s	0	§4.4. small "s": Gutenberg (1945a) ~20 s period s.w.; Ms_20
		Ms	MS	M_S	→	M_S	S	surface wave	M_S	0	§4.4. Big "S": broadband s.w. (Ms_BB), or (older sources) mis-capitalized M_s
Ms_20	Ms	Ms	Ms	M_s(20)	→	M_s20	s20	surface-wave 20s	M_s20	0	§4.4. 20 s period s.w. mag. per IASPEI
Ms_BB	Ms	--	MS	M_s(BB)	→	M_sBB	sbb	surface wave broadband	M_sbb	0	§4.5. Broadband s.w. mag. per IASPEI
		Mz			→	M_z	z	surface wave, vertical	M_z	0	Measured from the vertical phase before that became standard.
Ms7				M_S7	→	M_s7	s7	surface wave	M_s7	0	Vertical phase on Chinese seismograph
		M_Sn			→	M_sn	sn	surface wave	M_sn	0	1-second period per Nuttli, 1983
		M_GR		M_GR	→	M_GR	gr	Gutenberg-Richter	M_gr	0	1954 G-R version of M_s. Includes M_PAS ("Pasadena")
		M_R			→	M_R	r	Rothe	M_r	0	Not "Richter"! Averaged M_s per Rothe 1969
		MLH			→	M_LH	lh	Russian M_s	M_LH	0	Parts of Russia (Obninsk)

Mc				M_c	→	M_c	c	coda length	M_c	0	§3.2.4.5
Md	Md	MD		M_D	→	M_d	d	duration	M_d	0	§3.2.4.5. Many variants. Not JMA displacement mag.
	M_t				→	M_t	t	tsunami mag.	M_t	0	§3.2.6.7. Used by PTWC
				M_m	→	M_m	m	mantle mag.	M_m	0	§3.2.8.5. Used by PTWC

	Me	Me			→	M_e	e	energy mag.	M_e	0	§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

	M_ms				→	M_ms	ms	macroseismic	M_ms	0	§3.2.6.6. Generic mag. estimated from macroseismic effects
		M_fa, FA		M_fa	→	M_fa	fa	m_b from felt-area	M_fa	0	Stover & Coffman, 1999. Est. from extent of felt-area. Multiple methods.
		M_La			→	M_la	`l`a	M_L from felt-area	M_la	0	M_L est. from intensity reports; for Calif. and Hawaii
		M_I			→	M_I	`I`	M_L from intensity	M_I	0	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

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 (ed.), 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.

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 articles in that category.

Usage

Examples

Data sources

Table of codes

See also