Talk:Richter magnitude scale
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Boffman 21:16, 25 March 2006 (UTC) March25 - reverted to old version due to vandalism.
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[edit] TNT energy table
What's the difference between Approximate TNT for Seismic Energy Yield and TNT equivalent of example? The numbers are significantly different in certain cases, and I'm not sure why we need both columns. -- nae'blis (talk) 16:20, 7 June 2006 (UTC)
Not sure if that table is right, it's reproduced a lot but the orders of magnitude in ergs don't add up. I agree with this table http://www.cwp.mines.edu/~john/empirical/node7.html
[edit] Richter Magnitudes
The table in this section has a column heading "Retro Earth magnitudes". This term does not appear anywhere else in the article, and I can't find a definition of it elsewhere (using Google). Either it needs to be changed to "Richter magnitude" or else "Retro Earth magnitude" needs to be introduced and defined before the table.
[edit] "estimate for a 10 km rocky bolide impacting at 25 km/s"
The TNT equivalent given here disagrees with the value given here by a factor of one-hundred.
If I've done the math correctly (?) than if the Tsar Bomb was 50 megatons it should have a Richter Magnitude of more than 10.
2/3*(log((4.2*10^12)*50,000,000)-4.8) = 10.348
So why is it catagorized as around 7? The Tsar Bomb link even discusses 4.2 megaton underground nuclear tests as resulting in siesmicity of around 7 -- so something's off about this table. 24.16.93.26 21:52, 18 January 2007 (UTC)
[edit] Rocky Bolide Math
Crunching the numbers:
A 10-km diameter bolide, with a density of 5 g/cm^3 (or 5 times the density of water. Iron is 7.86 g/cm^3, the Earth is 5.5), has a mass of about 2.6*10^12 g. Traveling at 25 km/s, the bolide would have an energy of 1/2 * m * v^2 = 8*10^20 J
At the rate of 4418 J / gram of TNT (See TNT equivalent), this generates 1.8 * 10^17 g of TNT = 0.18 teratons (metric) of TNT, give or take 20%. So in order to generate the requisite 1 teraton of TNT-force on impact, a 5-fold increase in the mass, or a 5^(1/3) = 1.7 increase in the radius, is a 17-km bolide. But given the limited precision of these calculations, I left it at one significant figure, or 20-km.
Lifthrasir1 19:40, 19 January 2007 (UTC)
[edit] problem with table
There are two examples of 5.0 with radically different numbers. Which is correct? —The preceding unsigned comment was added by 134.219.128.121 (talk) 12:58, 23 January 2007 (UTC).
[edit] The base of energy release of the Richter scale is empirical and is over 30
The relationship of the base of the Richter scale to energy release is empirical. Estimates put the base at slightly more than 30. In other words, an increase of two on the scale is over 900 times as much energy release. Although the base is stated several paragraphs into the article, since this is a very significant practical fact, it might be good if it appeared earlier. A lot of the confusion about energy release (see other talk posts) is probably traceable to the article leading off by saying that the base of the scale is 10, and people casually assuming that this is the base of the energy output rather than the amplitude. Brian Hill 07:37, 7 March 2007 (UTC)
