Talk:Peak ground acceleration

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Earthquakes Mid‑importance

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How useless

If someone wants to study these, should enroll to the relevant university and complete the PhD. These factoids in Wikipedia are useless: those who know it, don't need it. Those who don't, well, for them it is useless. Instead of showing off your knowledge, just give a short explanation the generic public can understand. Just for the info of these show-offs: Wikipedia is NOT accepted by any reputable university as a source.

G forces

It appears the chart for g forces is backwards as the g forces are lowest on the most sever earthquakes and highest on the less sever earthquakes. But I am no expert. Philip964 (talk) 17:55, 13 March 2011 (UTC)[reply]

No, the values are accurate. Earthquakes are complicated - the magnitude relates to energy released and is an absolute value; PGA refers to actual ground motion caused by the earthquake in various areas, which differs according to how deep the quake is, how far an area is from the epicentre, and the types of soils/rock. Structural damage is linked more closely to PGA than magnitude, which is why we see, for example, much more devastation and earth in the 6.3 Christchurch earthquake than the 7.1 one hitting the region 6 months earlier. Gwinva (talk) 22:06, 13 March 2011 (UTC)[reply]

Sendai earthquake

For the Sendai Earthquake, I'm not sure where that 0.35g acceleration is coming from. It's not clear on the map and from what I'm hearing there might be much larger accelerations than that.Stardude82 (talk) 20:55, 13 March 2011 (UTC)[reply]

I have no idea either - I removed it. I'm sure in the days to come we will find something more accurate. Gwinva (talk) 22:06, 13 March 2011 (UTC)[reply]

I have put in a (referenced) figure of 0.53g for what I think is the highest PGA for any of the seven nuclear plants monitored. It looks from Fukushima I Nuclear Power Plant as if the design limit there was 0.18g Thincat (talk) 10:21, 15 March 2011 (UTC)[reply]

Thanks, but I've changed the cite: that source keeps altering its figures and assesses only 7 sites; I've gone with teh University of Tokyo figure. Gwinva (talk) 23:38, 15 March 2011 (UTC)[reply]

Japan Meteorologiac Agency said that 2933Gal(29.33m/s^2) was measured at Kurihara city, Miyagi prefecture. This city had shake of Shindo scale 7 of JMA, which was the largest in the Sendai Earthquake. http://outreach.eri.u-tokyo.ac.jp/ul/EVENT/201103_NIED_0313.pdf Someone please check it. 223.133.44.218 (talk) 08:19, 18 March 2011 (UTC)[reply]

Thanks for the link. 2933 Gal is unheard of, and it doesn't tie in at all with what USGS, and other seismologists have said, or what and Univ. Tokyo have said in other sources. The Japanese/English graphs and data are not clear. Will investigate further. Gwinva (talk) 09:56, 18 March 2011 (UTC)[reply]

An English page of the Earthquake Research Institution, Univ. Tokyo here. http://outreach.eri.u-tokyo.ac.jp/eqvolc/201103_tohoku/eng/ Is it enough or I'm saying something beside the point?(No offence but I'm just not good at English) Do you mean I should just wait for updates of USGS or Univ. Tokyo? 223.133.44.218 (talk) 12:04, 18 March 2011 (UTC)[reply]

The Japanese wikipedia is quoting 2933 Gal[1], translated into English here, with three references. I don't have time now to follow this up and my complete ignorance of Japanese is more than a hindrance! Thincat (talk) 16:39, 18 March 2011 (UTC)[reply]

Someone has (properly, I think) added this to the article and I have added a second reference. Here are some more.[2][3][4] Thincat (talk) 19:25, 18 March 2011 (UTC)[reply]

Looking at data from usgs the PGA doesn't get over 272 cm/s/s when 1 gal is 1 cm/s/s and measured at earths surface we have 976 gal this figure of doesn't make sense I think we should wait before publishing any figures —Preceding unsigned comment added by 203.109.220.246 (talk) 20:30, 18 March 2011 (UTC)[reply]

I have some sympathy with what you say but I still think at present the figure should be given. Wikipedia is here to report reliable sources and we have multiple such sources. We are not here to review the science. However the multiple reports are of a single instrumental reading: an instantaneous peak value from a single accelerometer of a value which can be regarded as a double differential. The value looks to me to be the maximum vector amplitude, not the horizontal component. I suppose the faster the response of the accelerometer the higher will be the peak. So, the figure may later be found erroneous, unrepresentative or subject to correction. None of this is for Wikipedia to do. Does USGS have an acknowledged international role in all this? The accelerometers are in Japan and are not operated by USGS (are they?). Is any reputable body disputing the figure? Is the reading actually not properly regarded as a PGA? We could, I suppose, footnote that the figure is provisional or that there are a wide range of purported PGAs. Finally, I see the Christchurch earthquake PGA figure is of a similar magnitude. Thincat (talk) 21:32, 18 March 2011 (UTC)[reply]

The source is a vector figure (3 components); this will make it higher. The others are single-direction figures (including the ChCh 2.2). I've removed for time being since we're not comparing like with like. We can add back in when we get something comparable. Gwinva (talk) 23:25, 20 March 2011 (UTC)[reply]

Please clarify where.

Words like "government" or "building codes" appear, but where does the matter apply? If you know, please clarify. Thanks beforehand. --Ahora (talk) 04:26, 17 September 2011 (UTC)[reply]

I've linked building codes but I think that the single use of 'government' is clear enough. The tag you added suggests that the article doesn't take a global view, but I can't see why you think that. Could you explain, so that the matter can be discussed here? Mikenorton (talk) 11:21, 17 September 2011 (UTC)[reply]

Hi. First, I'm not involved in seismology or architecture by trade.

1. "ShakeMap": from this site, ShakeMap is a word coined by U.S. Geological Survey Earthquake Hazards Program. Similar things are likely to be found elsewhere, but at least it must be US.

2. It must be true that pga is used to set building codes in some countries, but where? (Any example will be good, and that's what I meant.) It's only in "wealthier" countries with frequent earthquakes, I'm afraid.

And for higher buildings, response spectrum to acceleration (I guess it's similar to resonant frequency) is more important, and at least in Japan, it's included in the law, together with pga.

To improve the article, it'd be good to separate laws and scientific facts.

3. DBEGM (or DBGM): from a short googling, this term seems to be used mainly in nuclear plant. So it turned out it's not directly related to global viewpoint issue, but first I suspected it. (In fact, it's NOT pga. It's merely a design basis, and is specified by pga, and has become in their circle a synonim of pga.)--Ahora (talk) 01:14, 27 September 2011 (UTC)[reply]

Add equations from research papers

Hi,

http://rds26.tripod.com/PGAEmpiricalRelationships.html

The above address cites papers and equations used to calculate PHA. It would be useful to include.

132.177.81.163 (talk) 16:58, 8 May 2013 (UTC) R[reply]

Probability of exceedence — Preceding unsigned comment added by 129.177.49.40 (talk) 12:10, 27 September 2015 (UTC)[reply]

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Direction of shaking

The article says:

"Earthquake shaking generally occurs in all three directions."

Which three? It doesn't seem obvious to me. Vertical plus horizontal gives only two. I'm reading this article exactly because I'm not familiar with how earthquakes work, so I shouldn't need to know beforehand. TooManyFingers (talk) 18:47, 29 May 2024 (UTC)[reply]