Talk:Surface-wave magnitude

Historical

Does it make any sense to apply this measure to earthquakes a long time ago, when no data was actually recorded? To me it doesn't, but see 1645 Luzon earthquake. John of Cromer in China (talk) mytime= Mon 13:44, wikitime= 05:44, 10 December 2012 (UTC)

Dimensional analysis

The given formula for M_s requires one to take the logarithm of A/T, where A is a displacement in μm and T is a period in s. It is accompanied by a note, stating, "It is obvious that the entire formula cannot stand dimensional analysis without additional qualifications."

Doesn't specifying the units in which the relevant magnitudes are to be measured already serve as the necessary qualification for dimensionlessness? For example, for a displacement of 480 μm and a period of 20 s we get A/T = 480/20 = 24. An entirely similar issue applies for the formula for moment magnitude, which also requires taking the log of a physical quantity measuring energy, for which, likewise, the units must be (and are) specified. The formula given there has no editorial note attached. Are there objections to removing the note here?  --Lambiam 09:59, 8 September 2017 (UTC)

I think we are in agreement it is a rather bizarre note for an encyclopedia. I haven't removed it because I think it shows just how bad this article is. It is also a poor indication that the two scholarly citations are in Chinese, even though this is the English Wikipedia, and the source documents for this topic are predominately in English. (There may be tags for these kinds of problems, but I haven't had the time to find them.) I would argue for a re-write. As you seem to know something about this topic, would you like to give it a try? If you don't have Gutenberg's papers handy I can give you urls. ~ J. Johnson (JJ) (talk) 22:45, 8 September 2017 (UTC)

My knowledge of the topic derives primarily from reading this Wikipedia article. The article could certainly use a good rewrite – if only to also bring in some historical perspective. What should be made explicit is that the formulas do not give a definition of the magnitude, but merely a way for seismological institutions to estimate the magnitude. I had a cursory look at some of the papers authored or co-authored by Gutenberg as well as some others by Vaněk et al., but all seemed to sport subtly different formulas. Also, all these papers were primary sources reporting on original research, and ideally we'd use (authoritative) secondary sources for our encyclopedia. I also looked at the USGS website, which has a long FAQ, but remains mum about the formula(s) they use. I am not confident I understand the issues well enough to do a good job based on primary sources, so I'll pass on your suggestion. I'll remove the note, though.  --Lambiam 20:49, 10 September 2017 (UTC)

I understand. There are decent secondary sources, such as the Chapter 3 of New Manual of Seismological Observatory Practice, 2nd edition (see Seismic scale#Sources for links), several encyclopedia articles, and some textbooks (e.g., Havskov & Ottemöller), but the problem is that even those are fairly technical. I have tried to make Seismic scale a broad but non-technical overview, letting the narrower magnitude scale articles to be more technical. Alas (or perhaps fortunately?!), those go beyond my competence. The USGS is of little help, as 1) they generally avoid any technical aspects (don't want to scare away anyone?), and 2) generally do not offer citations. (It seems they think verification is something the public can't handle.)

You're right that the formulas don't define the scales. (Especially as it seems that every author tweaks the formulas.) The main difference in most scales is what they are measuring (maximum wave amplitude? only P-wave amplitude? Lg-wave? integration over the entire wave train?) and how (horizontal or vertical? peak-to-peak? 20 seconds or "broadband"?). All quite interesting, and should not be overlooked in a specific article. Surface-wave magnitude is particularly challenging in that regard, having been punched up in so many ways over the years. It probably needs a dedicated expert. I wonder if we could find some recently retired seismologist who has a bunch of time. ~ J. Johnson (JJ) (talk) 23:00, 10 September 2017 (UTC)

Needs appropriate sources and a rewrite

This article needs rewriting, but more fundamentally it needs better sources. It provides some technical details, but does not properly attribute them to the original developers of this scale, nor mention any of the historical context, or any of the characteristic of the scale. It relies primarily on two Chinese sources, in Chinese, which is inappropriate for the English Wikipedia, especially as the original sources are in English and readily available. I am tagging this to get more attention (as I don't know when I will have time to rewrite this). If anyone is interested I can point to the appropriate sources. ~ J. Johnson (JJ) (talk) 20:02, 25 November 2017 (UTC)

Re move

@Ravenpuff: perhaps you would inform us as to which "certain reliable sources" you relied on move this article to the hyphenated form? I point out that usage in the seismological literature seems mixed, and I am not aware of any definite preference for one form or the other. ♦ J. Johnson (JJ) (talk) 19:47, 18 February 2020 (UTC)

You're absolutely right in saying that the literature is mixed, but I believe that there's a case to be made for the hyphenated version to be used – the Manual of Style (MOS:HYPHEN) stipulates that "compound modifiers" should be hyphenated, correctly implying in this case that "surface-wave" modifies "magnitude". The unhyphenated form ("surface wave magnitude") could be incorrectly taken by unfamiliar readers to mean a "wave magnitude" located at a surface. — RAVENPVFF · talk · 18:05, 19 February 2020 (UTC)