Talk:Seismic magnitude scales

Shindo scale

I believe "Shindo Scale" should be renamed "JMA" or "Japanese Meteorological Agency" scale, as I believe "Shindo" is a generic Japanese term for earthquake intensity that can be used to refer to other scales, and I've not found any signs of "Shindo" being an official English term. See also my comment at Talk:Japan_Meteorological_Agency_seismic_intensity_scale Identity0 (talk) 03:56, 15 August 2008 (UTC)

Change name?

In the course of other work I have become more aware that the measure of earthquake strength/size as "magnitude" (M) is not as simple as one might gather from the popular media: there are at least a dozen definitions of earthquake "M". This article addresses that, but I find "seismic scale" to be a term of near insignificance, notable (in a Google search) mainly in connection with this article. Therefore I would like to propose a name change. I am not settled on what would work best, but currently lean towards "Magnitude (earthquake)" or "Magnitude scale (earthquake)". Other variations seem reasonable, and some of them, and the current title, could be redirects. Comments? ~ J. Johnson (JJ) (talk) 21:43, 19 December 2012 (UTC)

How about "Measuring earthquakes"? Mikenorton (talk) 22:22, 19 December 2012 (UTC)

Well, that is what these scales attempt to do, though that could also refer to a seismometer. But I rather doubt if anyone comes here (or to WP) asking "how to measure an earthquake". More likely they have seen something like "a magnitude 6 earthquake". Or us editors want to wikilink "M 6.3" to something that explains what that means, and M really does mean "magnitude". (Though so do a lot of things.) So my thinking is that the destination (this article) should stay close to that. ~ J. Johnson (JJ) (talk) 20:04, 20 December 2012 (UTC)

Fair enough. We could go for the clunky, although fully explanatory, "Earthquake magnitude and intensity scales", with appropriate redirects. This assumes that we still want to have these two very different measures together in one article (which I think is probably the right solution). Mikenorton (talk) 21:50, 20 December 2012 (UTC)

Let's not go for clunky. Covering different ways of measuring earthquake "size" (distinct from the different scales for calibrating these measurements) is good, because each of these ways has valid usage, and this article is a good place to explain that. I am not certain that "magnitude" is distinct from "intensity". We should probably consult some seismology books for guidance. The USGS has some limited comment here. ~ J. Johnson (JJ) (talk) 23:22, 21 December 2012 (UTC)

On formatting M

Regarding the symbol M used for earthquake Magnitude: do we have any notions of best practice on how it should be formatted? (E.g., italic or straight, spaced or closed-up, ??) Should subtypes be subscripted, or not? (E.g.: M_L vs. ML, etc.)

Is there any interest in having a template to handle the details? Perhaps for tracking articles that use M? ~ J. Johnson (JJ) (talk) 20:47, 16 April 2016 (UTC)

I'm probably not going to be of much help here, but I think that's a great idea. I have found myself formatting it different ways, so anything to help uniformity. I just don't really know what the options are, or how it would work if we had a template. Is there something similar in use anywhere on WP? Dawnseeker2000 22:57, 18 April 2016 (UTC)

I am not aware of anything similar, but that is hardly surprising. What I have in mind is something like {{M|x|yyy}}, where the optional "x" would be any of several subtypes and "yyy" is any appropriate string. E.g.: {{M|w|> 7.0}} would yield "M_w > 7.0", each element concatenated with a non-breaking space. Formatting to be whatever is deemed best. There is already an {{M}} template, but I think that can be made available. ~ J. Johnson (JJ) (talk) 00:50, 19 April 2016 (UTC)

So if we decide to use a template, we'll have to through some long drawn out discussion on the what's and the why's. Hmm, I definitely think there's some room for improvement with this though. I used to not like using subscript in the text because it made a minor but noticeable change in line spacing. That's been sorted out now. So, let's see what, if any, other folks have to say. Then I'm interested in seeing some proposals. Dawnseeker2000 02:47, 19 April 2016 (UTC)

Rather than describe a template I would rather produce a prototype that can be seen in action (details to be worked out). But in that this requires re-purposing of an existing template I would like to see that there is some support. So far it looks like everyone is asleep. ~ J. Johnson (JJ) (talk) 20:49, 19 April 2016 (UTC)

Approach: treat as physical quantity symbol

• M for magnitude is a quantity symbol, and so should be italics: M. Specifiers like L, 0 and w are subscripted and upright (Roman) font: M_L, M₀, M_w. See SI brochure. Preferably the subscript is lowercase, but capital L is accepted to prevent confusion.
• Being a quantity symbol, it should not be used as a unit. The formula is:

physical quantity = number × unit.

Since M is dimensionless (or so they say), the unit is 1 and can be omitted from the equasion. In symbols:

M_L = 8.0

Note that the quantity symbol is rarely used, more often its name is used:

magnitude = 8.0

Incorrect is: magnitude = 8.0 M_L N, it's not the unit.

{{Infobox earthquake}} invites for this misunderstanding. Better would be, like:

Magnitudes demo
Label	Value
Magnitude (Mw)	6.1
Magnitude (Mw)	6.2
Magnitude (ML, Richter)	6.2

-DePiep (talk) 20:32, 1 June 2017 (UTC)

Interesting points. I was working on standardizing our usage of "M" up until last October, but have been seriously distracted. I'll see if I can get back to this RSN. ~ J. Johnson (JJ) (talk) 22:14, 1 June 2017 (UTC)

I'll drop some more considerations here.

1. The SI Brochure may be incomplete for this. Browsing the BIPM site (the authority) may give more info. Must say, this info is scattered and not always definitive -- some freedoms remain.
2. {{M}} (talk) be renamed (moved) to Template:Magnitude?
3. {{M}}'s potential use is low.

First, good writing is "magnitude (M_w) = 5.3" or "M_w = 5.3". (the symbol is always on the lefthand side)

In practice, 90% of situations writes "magnitude (+ some specification) = number", i.e. the name (wording) not the symbol. That wording can be wikilinked of course.

Also, often <math> is used to write the formula. In general, it takes editor's eye not a simple template.

4. In {{Infobox earthquake}} (talk) (600+ P), we could add dedicated parameter(s) like |magnitude Richter= to be clear right from the first editing. |magnitude= then can mean M_w by default. Also allows nice labeltext (lefthand) for Richter.

5. I doubt whether M_w is dimensionless, as is stated so often even in Moment magnitude scale (but not in the defining source, ref #1 Hanks, Thomas C. (1979)). In short: the number measured is M₀ having unit dyn×cm, that is: g×cm/(s²)×cm or dimension MLT^-2L or ML²T^-2. (M=mass, L=length, T=time). Then, since M_w is ... log₁₀(M₀) ..., its unit & dimension follows: dimension = log₁₀(g×cm/(s2)×cm). So dimension is log₁₀(ML²T^-2). This may be incomprehensible, but formally correct. (It could become dimensionless if one divides it by a similar standard unit, which would cancel out mathematically the unit & dimension).

-DePiep (talk) 08:06, 2 June 2017 (UTC)

Hey, you're getting way ahead of me! I don't even have my pants on (so to speak), let alone my running shoes. It is going to take me at least two weeks to get some other work cleared out of the way, and then I'll need to review what I have in the way of sources. But a question for you: does SI explicitly cover earthquake magnitudes? Or does it make general suggestions regarding this kind of stuff?

As a comment, I would be solidly against renaming {M} to {Magnitude}. The latter is general term, encountered much more broadly than just seismology, while the use of "M" seems to be predominately seismological and astronomical. (And I seem to recall that there is, or could readily be, an alternative for astronomical uses.) Note the typical situation here: editors not conversant with the different varieties of "M" copy it from popular sources, and for the most part would likely be resistant adding something like {Magnitude|...}. On the other hand, it is much easier and liklier to get editors to add "{M}" (with the braces doubled, of course), which puts it into a maintenance category where someone more knowledgable can adjust it as appropriate. ~ J. Johnson (JJ) (talk) 23:10, 2 June 2017 (UTC)

Sit down, take your shoes off. I am only commenting (for now...).

{M} or {magnitude}: up to you. it's about: "M" vs. "magnitude" or "earthquake magnitude": whatever fits best. (I predict less usage when using "M". And as said: less overal b/c of situations mentioned).

SI does not mention magnitude or M. It says:

physical quantity = number × unit

physical quantity name = number × unit name

physical quantity symbol = number × unit symbol

→ M_w = number × 1

SI points are:

1. always keep the algebraic equasion in mind: quantity = value [next: value = number × unit]

2. don't mix up lefthand vs. righthand stuff: speed (v) = number × m/s [quantity =/= unit]

-DePiep (talk) 23:32, 2 June 2017 (UTC)

(No, I didn't forget about this! I've been wrapped up in deep consideration. Okay, here's where I've gotten to.)

I am quite ambivalent about italicizing. I contemplated it before, but there are some complications, and I felt it is much easier to not italicize. Note that while scientific journals tend to italicize, popular media, including press releases from the USGS and other authorities, generally do not. And for historical reasons seismologists are used to labels without italics. So part of the consideration here is the degree to which we desire to emulate journal standards. I don't believe we need full adherence (and likely should not), but I am not against some degree of exactness.

I think I understand what you mean by "M for magnitude is a quantity symbol", but the matter is not quite that simple. Note that saying "magnitude = 8.0" without specifying which scale (except in the popular media, which often doesn't know any better) is no better than saying "temperature = 32 degrees" without specifying Fahrenheit, Celsius, or Kelvin. In that sense saying "a magnitude m of 8.0 Richter" is just as sensical as "a temperature t of 80 degrees Kelvin". The problem is that "Richter" is not a unit (it's a scale of unequal units), so it fails the SI definition of a quantity as "the product of a number and a unit". What we have is an ordinal quantity, per §3.26 of the ISO "Quantities and units", where "Earthquake strength on the Richter scale" is cited as an example. (Though I wonder if measurement scale, per §3.27, is more appropriate.)

So the question we have is: how to specify some value ("quantity") M on scale N, where we have in mind the general model of "M_N".

Part of the problem I'm having hinges on whether the concept here is "a magnitude M (or m) on a scale of (pick one) L/w/B/b/bi_BB/b_Lg/etc.", or "a magnitude on a Magnitude scale of ML/Mw/mB/mb/mb_BB/mb_Lg/etc." E.g.: do we have scales M_L and M_w, or L and w? One implication is whether we do:

1) mb_Lg.

2) m_b(Lg) (BSSA style, which I don't like because it makes the subtype (Lg) more prominent than the type (b)).

3) A variant such as m_{b_Lg}.

4) Or something else. (See table 3, p. 12, in IASPEI Information Sheet 3.3 for some examples.)

At any rate, I think the subscripting needs to be reviewed (and likely revised). While I am not quite convinced to italicize, it will be easier to do with the subscripting resolved. What do you think? ~ J. Johnson (JJ) (talk) 23:01, 10 June 2017 (UTC)

Will reply later on. -DePiep (talk) 16:23, 14 June 2017 (UTC)

J. Johnson By the way, could you give a link or number of that ISO? I'm living by SI. -DePiep (talk) 20:36, 14 June 2017 (UTC)

That's ISO 80000-1:2009(E), available here. ~ J. Johnson (JJ) (talk) 21:33, 14 June 2017 (UTC)

A great paper! Nicely expands on the SI setups. -DePiep (talk) 11:43, 6 July 2017 (UTC)

• Recap. IMO our current core points are: 1. how to format symbols like M_w and M_L, e.g. use italics or not. 2. how to write a magnitude value correctly, in formula and in words. (Minor issues are, let's not get distracted: use a dedicated template like {{M}}, type of the scale being magnitude, change infobox, dimension doubts). For now, I think we can limit ourselves to the Richter and moment scales (I am unfamiliar with the other ones like mb_Lg. I'd have to look into those).

1. Formatting the magnitude (M) symbols. Sure "M" alone is not enough, because it needs a scale specifier. Still, it does say it is "a magnitude" quantity (when in context). The M magnitude can be specified into moment or Richter: M_w or M_L. These are called the symbol for the physical quantity (this is my main point!). Symbol, as opposed to the name of the physical quantity: "Moment magnitude scale", "Richter magnitude scale".

Now for the formatting, I turn to ISO 80000-1:2009(E) (nicely provided by J. Johnson), chapter 7: Printing rules, says:

7.1.1: "Symbols for quantities are generally single letters from the Latin or Greek alphabet, sometimes with subscripts or other modifying signs". That's the M and w and L.

"The quantity symbols are always written in italic (sloping) type, irrespective of the type used in the rest of the text". So we write: M (italics).

The font-type is not prescribed, so both sans-serif and serif are allowed: M and M. A serif font is used by <math>: $M_{\mathrm {w} }$. Of course we follow the Wikipedia stylesfonts, instead of introducing fancy fonts.

7.1.2: "Subscripts: When, in a given context, different quantities have the same letter symbol or when, for one quantity, different applications or different values are of interest, a distinction can be made by use of subscripts."

"A subscript that represents a physical quantity or a mathematical variable, such as a running number, is printed in italic (sloping) type. Other subscripts, such as those representing words or fixed numbers, are printed in roman (upright) type". I think this defines that the w and L should be Roman (upright), not italics.

TL;DR: So we write M_w, M_L, formatted: ''M''<sub>w</sub> or <math>M_\mathrm{w}</math>. Can you agree? -DePiep (talk) 11:43, 6 July 2017 (UTC)

re remaining remarks made by J. Johnson above. ...ambivalent about italicizing, ... complications. I don't think these complications prohibit correct writing. it is much easier to not italicize is not that convincing (I even disagree), instead I'd say "write correct when we have a correct form". Also, this helps to format consistently throughout Wikipedia. ...popular media, including press releases from the USGS and other authorities, generally do not italicize, well, lets follow the sources then, especially since it is a scientific topic. Sure historically and in older sources, the formatting might be different. But why cling to that form, while we do have developed a well-thought system of formatting? Why should we allow variant writings at all? Following popular media and so changing away from SI/ISO defined style: no gain, and no support (in the say WP:SCIENCE community). Could it be that you are very much used to alternative format, and that I only ask you (and other WP:EARTHQUAKE editors) to accept the single well-defined form?

Todo: apply or check this ISO/SI prescription to the other magnitude scales. -DePiep (talk) 11:43, 6 July 2017 (UTC)

About the sources (RS): it occurs that reliable sources like Harsh Gupta, Encyclopedia of Solid Earth Geophysics and Hanks, Kanamori (1979): A Moment Magnitude Scale are varying the subscript style: for example subscripts like "w" is either italics or Roman/upright. I'd say this is of sub-minor importance, as in: a slip of the typography. These papers are not about formatting a subscript! Given the sound physics paper they are, these are mistakes, not a redefinition of the format. So we can stick to the ISO/SI M_w format. An other RS is Bormann et al. (2013): Seismic Sources and Source Parameters. For M_w, it writes "Mw": upright-M, and not-subscripted-w. So I doubt it the other symbols mentioned in there are formatted definingly (or even exemplary). -DePiep (talk) 16:51, 6 July 2017 (UTC)

2. Writing the magnitude value correctly. (later more, about wording and the lefthand-righthand side etc.). -DePiep (talk) 11:43, 6 July 2017 (UTC)

Meanwhile

• Meanwhile I did this and this to a FA while Featured! -DePiep (talk) 16:23, 14 June 2017 (UTC)

And the music didn't immediately die? Fabulous!

I would take those as explorative demonstrations; will comment there. ~ J. Johnson (JJ) (talk) 21:35, 14 June 2017 (UTC)

DePiep: I recently ran across this comment by William Ellsworth (in USGS Professional Paper 1515, p 176):

Quantification of earthquakes and magnitude scales
To relate the characteristics of one event to another, the observed quantities must generally be summarized through the use of either an empirical relation, such as magnitude, or a quantity derived from a physical model, such as seismic moment.

It seems to me this is right on point regarding what you raised earlier, as to whether magnitudes are "physical quantities" (and therefore "quantity symbols"). Comment? ~ J. Johnson (JJ) (talk) 02:37, 6 July 2017 (UTC)

It seems trivial that when one wants "to relate the characteristics of one event to another", one must compare the same quantity (or whatever).

I understand you want to point to the either ... or opposites: it says "empirical relation, such as magnitude" is not "a quantity derived from a physical model, such as seismic moment". Do you think this says: magnitude is not a physical quantity? (correct me if I'm wrong).

Now for my point, which is only about noting a physical quantity, not about where that quantity comes from (an empirical measurement, or a model). For this, I claim that both "magnitude" (specified, e.g. Richter) and "seismic moment" are both physical quantities, albeit incomparable (different dimension for starters).

Maybe Ellsworth is writing about the challenge to connect the model and the empirical measurements, and how to relate those two values for one earthquake. Very relevant, but not changing the need to write each quantity (magnitude, seismic moment) right.

Did I answer your point? -DePiep (talk) 09:37, 6 July 2017 (UTC)

Referencing (citation) style

This article's current referencing is anemic (note the 'refimprove' tag), and underdeveloped. I am thinking of adding some sections on seismic magnitude scales not covered in other WP articles (and probably not notable enough for an article) in the course of which I would be adding multiple sources, used multiple times. To that end I would be restructuring the citations, and adding short cites by way of {{Harv}}. Seeing as no one has stepped up to fix anything since the 'refimprove' tag was added in 2008 I expect there will not be any objections to my augmentations. ~ J. Johnson (JJ) (talk) 00:02, 3 June 2016 (UTC)

Information

I would like for information to be added about M_bLg, M_B, M_fa, M_N, and others, as well as their differences. I may do this myself at some point, but just so I can remember and in case someone else wants to make relevant additions, I thought I'd mention it here. Dustin (talk) 04:24, 2 October 2016 (UTC)

Yes. I was working on this up to last October, but got distracted, and only now saw your note. I'll see if I can get back on that horse. :-) ~ J. Johnson (JJ) (talk) 22:17, 1 June 2017 (UTC)

Lede

@DePiep: A couple of points re your edit of the lede. First, your "define, measure, and describe" is rather pedantic. A scale is a measure of magnitude, but the lede is not the place to define what magnitude is. (or even what a scale is.) It is sufficient to just give the reader a short, easily grasped handle on what the topic is; "measure" suffices. Second, listing the types of scales as "one [is something] intensity", and "one [is something] magnitude"" is really weak: at the front of the sentence (which is the most powerful point) that compares "one" with "one", which carries no more information than a pair of bullet points. The essence of these two kinds of scales are "intensity" and "magnitude", and putting them up front makes a stronger, clearer, statement. I am going to adjust that; hopefully you will find it acceptable. ~ J. Johnson (JJ) (talk) 19:49, 23 June 2017 (UTC)

re J. Johnson

re ... the lede is not the place to define what magnitude is. (or even what a scale is.). And that is what I did not do. In the first sentence, I did describe what the [article title] is: "A seismic scale is used to define, measure and describe the strength or "size" of an earthquake" [1]. How does that relate to your remark? By now, I think "define and measure" would be more to the point, and adding the quoted "size" is too off-topic (introducing vagueness; it really tries to say 'sort of').

re one, ...one: yes that was weak.

re: "define, measure, and describe" is rather pedantic ... "measure" suffices. Then why do you use "intensity scales that describe ..." and "magnitude scales that measure ..." between the two equal types?

re your ... is rather pedantic. A jab that could be perceived as a personal attack even. Actually, this introduction your opinion is rather self-pointing. You are welcome to propose & discuss improvements, but adding a personal opinion does not help and is distracting from any point you otherwise try to make. -DePiep (talk) 08:07, 25 June 2017 (UTC)

Get a grip. I expressly referred to specific language ("define, measure, and describe"). If after eliding that language you perceive the remainder as some kind of personal attack then I suggest you not elide it. I would also point out that accusing someone of a personal attack can be taken as a personal attack. Which is all beside the point. What you seem to have missed is that we don't really need all three of those verbs.

I used "describe" and "measure" as being most appropriate for two classes of scales that are not "equal types". Magnitude scales are (generally) based on actual, objective, and quantitative measurements (such as the amplitude of a seismic wave). Intensity scales are descriptive, based on what kind of effects were subjectively observed. ~ J. Johnson (JJ) (talk) 22:44, 25 June 2017 (UTC)

It would be better to use "Richter" instead of "Richter scale"

I've recently entered the earthquake domain, coming from the physics department (actually: as a formatting fanatic). So I've met and studied the topic, especially the seismic scales.

I kept having troubles with understanding these scales. And this is what makes it more difficult. The domain community keeps adding "... scale" to every measurement. So a Richter value (correct wording!) still must be tied to that awkward "Richter scale" thing. That produces "A quake strength 7.0 on the scale of Richter", while equally correct one can say "A Richter 7.0 quake". The solution: drop the scale word and you are free.

A parallel. In temperature (also a physical quantity), we can say: "37 degrees on the scale of Celsius" (that's 100 degrees on the scale of Fahrenheit BTW). How often do you actually do that? Never! Drop the 'scale' word, and you can say: "37 degrees Celcius".

To push my point, I could propose a title change: move Moment magnitude scale into Moment magnitude (of course the article will explain its scale used, in a subsection). -DePiep (talk) 17:29, 6 July 2017 (UTC)

Re hatnote reversion

Re your reversion of my hat note: linking to "WP-internal documenation" is not prohibited, is even common place. A few quickly garnered examples:

• At Parenthetical referencing:

For the use of parenthetical referencing on Wikipedia, see Wikipedia:Parenthetical referencing.

• At Style:

For the Wikipedia style guide, see Wikipedia:Manual of Style.

• At Table:

For use of tables to display information in Wikipedia, see Wikipedia:Tables.

However, you did remind me that I should have used {{selfref}}, so I will make that correction. ~ J. Johnson (JJ) (talk) 20:07, 6 July 2017 (UTC)