Template:Earthquake magnitude

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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 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

• {{ 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.

 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 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 "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=}}→ 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 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. 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_?	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			→	Muk	uk	Unknown	M_uk	0	Source says "unknown" scale. Might be 1954 MGR mag. See here.
ML	Ml	ML	ML	ML	→	ML	l	Local ("Richter")	M_L	0	§4.1 "Local" to Southern Calif. Adapted for other regions, but not necessarily comparable.
	MJMA	Mj		MJMA	→	MJMA	jma	JMA "Local" mag.	M_jma	0	§3.2.4.7 Japanese Meteorological Agency. Also MJ, but not Mw(JMA).
				M0	→	M0	0	seismic moment	M_0	0	"M zero". A physical value, basis of Mw. In Newton-meters or dyne-centimeters
		M		M	→	M	.	moment mag.	M_w.	0	dot: implicit Mw.
Mw		Mw		Mw	→	Mw	w	moment mag.	M_w	0	§4.7 Generally preferred when available. Use only if "w" is present.
		Mwb			→	Mwb	wb		M_wb	0	Mw calculated from body-waves
		Mwc			→	Mwc	wc		M_wc	0	Mw from centroid moment
		Mww			→	Mww	ww		M_ww	0	Mw from W-phase centroid
		Mwr			→	Mwr	wr		M_wr	0	Mw at regional distance
		Mwp			→	Mwp	wp		M_wp	0	Mw from broadband P-waves §3.2.8.2
Mwpd					→	Mwpd	wpd		M_wpd	0	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	0	§4.3 Case sensitive: use "b"
mB	mB	--	M	Mb(BB)	→	mB	B	body-wave, broadband	M_B	0	§4.2 Case sensitive: use "B"
mB_BB	mB	--	M	Mb(BB)	→	mBBB	bbb	body-wave, broadband	M_Bbb	0	§4.2
mb_Lg	mbLg	mb_Lg, MLg		mb(Lg)	→	mbLg	blg	mb from Lg wave	M_bLg	0	§3.2.4.4; §4.6 North America east of the Rocky Mountains, and other cratons
		Mn	MN		→	mN	n	Nuttli (1973)	M_N	0	§3.2.4.4; §4.6 Same as mbLg
mBc					→	mBc	bc	Cumulative body-wave	M_Bc	0	§3.2.8.1
				MS	→	Ms	s	surface wave	M_s	0	§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	0	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	0	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	0	§3.2.4.5 Many variants. Not JMA displacement mag.
						Mt	t	tsunami mag.	M_t	0	§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	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
						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	0	Est. from extent of felt-area. Multiple methods.
		MLa			→	Mla	la	ML from felt-area	M_la	0	ML est. from intensity reports; for Calif. and Hawaii
		MI			→	MI	I	ML 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

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 (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.

See also

• Category:Articles using templated earthquake magnitude scale
• Seismic magnitude scales. Brief descriptions of the most common magnitude scales.
• Template:Cite anss For citing data from the USGS-ANSS Comprehensive Catalog.
• Template:Short-anss In-line short-cite.
• Template:Cite isc For citing data from the International Seismological Centre.
• Template:Short-isc In-line short-cite.

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