# Talk:Hypocenter

Latest comment: 5 years ago by InternetArchiveBot in topic External links modified

## Ground Zero

Is there any use of "hypocenter" to describe an explosion's ground zero other than the atomic bombings of Japan? This seems to be the only place it is used this way. (Presumably the hypocenter of a sub-surface detonation would be the detonation point, rather than the ground zero.) 214.4.238.180 (talk) 21:58, 21 June 2012 (UTC)

I can't remember the title, but I saw a film (or documentary) about the Manhattan project and the subsequent cold war with its atmospheric nuclear testing - or maybe it was about the increase in the numebr of cancer cases in the town of St. George, Utah. Anyway, the scientists used the term hypocenter quite a lot in the film/documentary. Sorry I don't have more detailed information. Astronaut (talk) 17:16, 26 June 2012 (UTC)

This is a paste of what I have put in the article on Ground Zero; it may be of use here? Incidentally I don't think you could have a hypocentre for a subsurface explosion but you could have a hypercentre - the point on the earth's surface above the detonation location?

The term was first used on the atomic bomb projects because the intended use of the weapon would be as an airburst. Therefore the jargon developed to talk about effects of the bomb at ground zero, ground plus 100 metres, ground plus 250 metres, and so on. Relative distance from the hypocentre (ie the ground) was used instead of an absolute altitude (eg 750 metres above sea level) as it is more meaningful. So to agree with Astronaut, we need a cited source - anyone? It jutifies the exchangeability of hypocentre and ground zero I think, and also casts a light on the more modern (and usually incorrect usage) of ground zero Mungo Shuntbox (talk) 12:43, 16 February 2013 (UTC)

## Totally useless.

I am really puzzled why this article has no statistical characterization of hypocenters. The only thing I learn is that they are "under" the epicenter. I guess that means they could occur at depths of up to 12,750 km??? Or do we only consider from the surface to the center of the Earth? Or do they not occur in the core? Or.... And what does "under" (focal depth) mean? Directly on a line from the epicenter to the center of the Earth? A cone centered on the epicenter? A cylinder? Is there a real link between epicenter and hypocenter? Really a very poor characterization, considering what we know today.173.189.72.242 (talk) 20:33, 16 April 2013 (UTC)

Could they occur "at depths of up to 12,750 km"? No. Earthquakes are a crustal phenomenom and the hypocentre is limited to being in the Earth's crust. The article adequately explains that the hypocentre is where the strain in the rock is released (ie. where the earthquake actually occurs). The epicentre is the point on the Earth's surface directly above the hypocentre, so if you were to draw a line from the epicentre to the centre of the Earth, that line would pass through the hypocentre.
Unfortunately, things are rarely as simple in real life. The area of maximum damage on the surface, might not be at the epicentre, and the long wavelength of the seismic waves and their variable velocity through different densities of rock can complicate things (especially if there is insufficient coverage of seismic recording stations). These factors can make it hard to precisely locate the hypocentre. Astronaut (talk) 17:25, 19 April 2013 (UTC)

## We need two separate articles (or none)

The article describes two completely separate uses of the word "hypocenter", and the two uses are almost contradictory. in geology, "hypocenter" is the point where the event actually takes place and "epicenter" is the spot on the ground. For nuclear explosions, "hypocenter" is (apparently) the spot on the ground, under an airburst.

This leads to two separate problems. First, we are close to a violation of WP:NAD. Then, even if we agree that one or both uses actually need WP articles, we are in violation of a guideline (that I cannot currently find) that dictates that two separate meanings of an article title should never be stuck in the same article.

Given the above, I intend to separate this article into two articles: Hypocenter (geology) and Hypocenter (nuclear explosion). After separation, I will then fix all the incoming links. After that we can choose to consolidate either or both of the resulting articles with articles in the related fields. -Arch dude (talk) 02:38, 23 July 2015 (UTC)

There's no doubt that we need an article on the seismological usage. It certainly can be expanded to discuss hypocentral depth ranges and how depths are determined. As to the other use it could be handled as a hatnote, directing interested people to ground zero. Mikenorton (talk) 06:32, 23 July 2015 (UTC)
In my opinion, those two meanings are sufficiently close that they can reasonably be covered in one article. The hypocenter is where the initial violent event (earthquake, nuclear explosion, aircraft collision, or anything else) occurred; the epicenter is the point on the earth's surface directly above or below the hypocenter. Maproom (talk) 10:08, 23 July 2015 (UTC)
Sorry, but that is (apparently) not the case for a nuclear airburst, and that is my problem. In an airburst, the violent event is above the earth's surface, but the "hypocenter" is at the earth's surface. "Hypocenter" is constructed from the prefix "hypo", meaning below or under. -Arch dude (talk) 05:01, 24 July 2015 (UTC)
Ok – I hadn't realised that. How confusing. Maproom (talk) 17:10, 24 July 2015 (UTC)

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