Wikipedia:Notability (earthquakes)

Earthquakes, when not cataclysmic, are exciting. Though earthquakes of magnitude 4 ("light": in general felt by many, but little or no damage) and greater occur over 14,000 times a year, in many areas they are uncommon. So even small earthquakes are often an experience that the people affected want to share, especially in areas where earthquakes are rare. But how many of these quakes warrant an article on Wikipedia?

The criteria for inclusion in Wikipedia is notability. General guidance for assessing notability is at WP:Notability (WP:N). Guidance for assessing the notability of events – such as earthquakes – is at WP:Notability (events) (WP:NEVENTS), which should be read before proceeding with this guidance.

The following explains the application of WP:NEVENTS to earthquakes, and the specific guidelines that have been developed to assess whether an earthquake is sufficiently notable for its own article.

Applicability of WP:NEVENTS

As with any other event, the principal criteria of an earthquake's notability are impact, and coverage.

Impact

The impact of an earthquake is not just its magnitude (power, or "size"), nor its intensity of shaking. It can be related to geographical scope (which is loosely related to magnitude), and here WP:EVENTS is explicit: "Notable events usually have significant impact over a wide region, domain, or widespread societal group." In regards of notability the geographical scope of an earthquake is important only for the extent of damage, or the number of people impacted. An earthquake impacting only a large swath of ocean bottom is not notable, nor one affecting only a few neighbors (even if they are spread out across much of Alaska). For notable earthquakes the geographical scope of "very strong" shaking (MMI ≥ VII) is roughly a hundred kilometers (60 miles) across, with significant damage or disruption of services at the epicenter.

Impact requires lasting effects. A great intensity of shaking would greatly affect those who experience it, but in itself is ephemeral, merely a passing event. And here WP:NEVENTS is specific: "A minor earthquake or storm with little or no impact on human populations is probably not notable." On the other hand, a small quake that causes a notable structure to collapse, or triggers a landslide that dams a river that floods a large area that leads to the founding of a dynasty (see Great flood (China)) has a large impact. (Although there might not be enough to say about the quake itself for an article. In such a case the impact is notable, but the event triggering it is not.) Note that "lasting" might not be determinable immediately following an event, especially regarding scientific significance. Breaching and flooding of the Tokyo subway system due to an earthquake would be an effect that could be confidently expected to be lasting, but the effects of most minor (M ~4) earthquakes are negligible to start, and rapidly fade.

Coverage

The notability of an event is assessed by coverage that is significant in having both depth and duration. Depth means coverage that goes beyond mere routine news reporting of the event, or inclusion in a list or catalog, to describe the impact of the event, or includes analysis that puts the event into context. Significant in-depth coverage is the basis of having enough material to write an article. Inability to expand a stub is an indication that the topic is not notable.

Duration means that coverage is not temporary or ephemeral, but continues beyond the weekly news cycle, and presumably reflects a continuing impact or interest.

Scientific impact/coverage

Independently of any societal impact, earthquakes can have scientific impact. Evidence of this could be a large number of entries in the International Seismological Centre's bibliography for that event. But note that these apply only where they are about the earthquake of interest, not merely mentioned in connection with something else. Where scientific notability is claimed for an event that otherwise lacks notability, that will need to be explained; this may require WP:secondary sources.

Other considerations

Biggest frog in a small pond

Comparison of an event to another event is problematical: any frog (event) can be made into the biggest frog in a pond, by making the pond small enough. Comparison of insignificant events – such as "The biggest earthquake in eastern Podunk County since the last barely noticeable earthquake" – does not confer notability. Nor is comparison with a notable event – such as "the largest earthquake in California since 1906" – necessarily significant, in that any earthquake will be "the biggest since" – until a bigger quake occurs. An earthquake "bigger than" another notable earthquake is likely notable on its own basis, but not because it merely has a bigger magnitude.

Small frog in a quiet pond

Even a smallish frog (event) can create a noticeable splash in a quiet – that is, aseismic – "pond". Note that the key factor is not the size of the "frog", but the level of "quietness" over some period of time. (Consider seismic gaps.) Notability might really be about the quietness of the other frogs.

Claims like "biggest earthquake in region X" tend to focus on earthquakes with epicenters in X, not on earthquakes with effects in X. While an earthquake's greatest impact is often near the epicenter, that is not always true. (In the 1989 Loma Prieta earthquake the greatest impacts were in Oakland and San Francisco's Mission District, and it was small consolation that the epicenter was 60 miles away.) To simply compare epicenters in a small area is misleading, as a distant earthquake might have equal or even greater impact. A better comparison would be of the shaking experienced from any earthquake, including distant but more powerful earthquakes. But such a comparison would be very localized, lacking geographical scope. And shaking that does not have a lasting impact is not notable.

Different measures of "big"

Seismologists use the moment magnitude scale – signified by some form of "M_w" – to rank earthquakes by nominal "size". However, earthquakes vary in how much energy is delivered to the earth's surface in the form of damaging shaking. In particular, deeper earthquakes have weaker interactions with the surface, and spread that energy over a larger area. Other magnitude scales, such as the surface-wave M_s or body-wave mb scales, are often better estimators of potential damage. (But see this comparison.)

Actual shaking is also dependent on the type of tectonic basement (such as cratonic versus non-cratonic) and local geology and sediments, while actual damage is also a function of the environment, built and natural. (E.g.: extensive URM – UnReinforced Masonry – construction is especially prone to failure and loss of life.)

As the impact of an earthquake on human society arises mainly from the degree and extent of quaking (which is only indirectly connected with the quake's magnitude), the best estimator of possible impact is probably the intensity of shaking over some areal extent. These can be estimated from the intensity and ShakeMaps on the USGS-ANSS website.

Fatalities are another measure of an earthquake's impact. These can be direct (due to landslides, or to failure of the built environment), or indirect (due to secondary disasters, or to consequent lack of medical care, food, or shelter). Fatalities are strongly dependent on factors beyond an earthquake's magnitude.

A handful of deaths might be due to a single vehicular accident, and (for the area affected) perhaps no greater than the usual death rate due to vehicular accidents, and likely not notable. On the other hand, a death toll of hundreds of people, even if only transiently notable, likely reflects a level and extent of damage of more enduring impact. (E.g.: the lasting impact of the 1933 Long Beach earthquake was not the ~120 fatalities, but the clearly evident potential for mass casualties in schools, which led to passage of the Field Act.)

Specific guidance

The primary criterion of notability is significant and enduring impact on human society, a subjective evaluation for which there is no definitive rule.

The following criteria are what experienced editors have found characterize notable and non-notable earthquakes. These are not requirements for notability, they are deemed generally correlative with notability.

[Indexing in draft is subject to change.]

a) Notable earthquakes garner national and even international coverage in the news, and over an extended period.

b) Inclusion in various earthquake catalogs and bulletins (or websites that echo the catalogs) is routine, and therefore does not indicate notability. However, not being listed in the USGS-ANSS "Significant earthquakes archive" or the ISC "Event index" is a strong indication of non-notability.

c) Shaking of intensity VII (MMI, EMS, or Chinese scales; Shindo 6-) or greater is generally necessary but not sufficient for notability. Remember that notability is not in the intensity of shaking, but in having some kind of enduring impact.

d) Shaking of intensity VII across an area of at least 50 km (30 miles) is probably notable, provided there are other impacts of an enduring nature.

e) M 8+ earthquakes are generally notable on account of a strong and enduring impact, with much coverage, but exceptions may exist.

f) M 7+ earthquakes are probably notable, but should meet additional criteria.

g) In the range of about 6.0 to around 7.5 magnitudes on the M_s, mb, mb_Lg, or M_e scales may be more correlative with shaking, and thus impact, than the moment magnitude scale (M_w) and its variants.

h) Earthquakes with M < 5 and no reported deaths or damage are very unlikely to be notable.

i) Earthquakes deeper than about 60 km have less impact on the surface than shallower earthquakes. Deep focus (plutonic) earthquakes (depth exceeding 300 km) may have minimal impact.

j) Cratonic earthquakes (generally in continental interiors, such as North America east of the Rocky Mountains) generally have stronger and more widespread effects than similar earthquakes elsewhere.

k) Scores of fatalities generally indicate a powerful, and probably a notable, earthquake (or poor construction), but a notable earthquake might not kill anyone, while even a non-notable quake might rack up a handful of deaths.

l) Being the biggest event in an arbitrarily selected locale or period ("since Y") does not confer notability. (See WP:BIGFROG.)

m) A significant earthquake occurring in a region not known for such earthquakes, or with a greater magnitude expected, or a recurring earthquake that returns much sooner (or later) than expected, may be scientifically notable on that basis, but this will have to be explained. Same for other earthquakes of scientific significance, but the significance might not rise to notability.