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The Richter Scale (NOT the Richter Magnitude scale)

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Geeksville
664934.  Mon Feb 01, 2010 4:50 pm Reply with quote

I have been searching high & low to confirm the true answer to this:

WHAT NUMBER DID/DOES THE ORIGINAL RICHTER SCALE GO UP TO?

This question is not to be confused with the scale we use nowadays. (The original 1935 scale was 'replaced' by the Richter Magnitude Scale in later years).

I really need the correct answer to this as I lost the pub quiz, because I was told the original scale only went up to 9.

As a full time nerd i have spent some considerable time looking into this and cannot find an upper limit on the original scale. Indeed I cannot find an upper limit on the Richter Magnitude scale either (although that is irelevant). What I can find is information stating the scale has and has never had an upper limit, it is only relevant to the earthquake it has recorded. The largest being in Chille in 1960 measuring 9.5 on the richter magnitude scale.

Help!

 
Moosh
664946.  Mon Feb 01, 2010 5:01 pm Reply with quote

There's no more reason for the Richter scale to have an upper limit than the Centigrade scale for temperature to have one.

However, you do often see explanations of the Richter scale written like this table I've taken from wikipedia (edited):

Richter magnitudes Earthquake effects
<2.0 Microearthquakes, not felt.
2.0-2.9 Generally not felt, but recorded.
3.0-3.9 Often felt, but rarely causes damage.
4.0-4.9 Noticeable shaking of indoor items, rattling noises. Significant damage unlikely.
5.0-5.9 Can cause major damage to poorly constructed buildings over small regions. At most slight damage to well-designed buildings.
6.0-6.9 Can be destructive in areas up to about 160 kilometres (100 mi) across in populated areas.
7.0-7.9 Can cause serious damage over larger areas.
8.0-8.9 Can cause serious damage in areas several hundred miles across.
9.0-9.9 Devastating in areas several thousand miles across.
10.0+ Never recorded

That one goes up to 10, but maybe most used to only go up to 9? I wonder people seeing something like that and thinking that it's "the Richter scale" may be the answer.

 
Ion Zone
664947.  Mon Feb 01, 2010 5:03 pm Reply with quote

You could look up the first machine for measuring it and then see if you can find a picture or a manual.

 
suze
664978.  Mon Feb 01, 2010 5:48 pm Reply with quote

Although there is no upper limit to the Richter scale, there is an upper useful limit.

I don't claim to understand the math - it's to do with gravitational binding energy, which will mean something to someone - but an earthquake which measured 18 on the Richter scale would destroy the Earth. So we needn't worry too much about values higher than 18.

 
brunel
665044.  Tue Feb 02, 2010 4:55 am Reply with quote

Actually, the quoted values for the 1960 Chilean quake are not based on the Richter scale, but have been revised and given as values on the Moment Magnitude Scale (shorthand is Mw).

What the Mw scale measures is the energy released from the earthquake, whilst the Richter scale used to measure the amplitude of vibration.
However, the Richter scale suffers from amplitude saturation, so the actual limit of what can be accurately measured on the Richter scale is 6.5-6.7 - beyond that, the values become increasingly unreliable, and essentially useless for any practical application (hence why Richter was abandoned so long ago).

And for those who are interested, the limit for the largest earthquake the Earth could ever generate would be around 10.5 on the Mw scale, which would require every single fault on Earth to rupture at the same time.

 
Curious Danny
665089.  Tue Feb 02, 2010 6:57 am Reply with quote

The Richter scale doesn't really deal with the massive earthquakes which is why the MMS is now used by scientists

 
crissdee
665229.  Tue Feb 02, 2010 10:23 am Reply with quote

brunel wrote:
......around 10.5 on the Mw scale, which would require every single fault on Earth to rupture at the same time.



And that would be bad, right?

 
brunel
665324.  Tue Feb 02, 2010 1:31 pm Reply with quote

crissdee wrote:
brunel wrote:
......around 10.5 on the Mw scale, which would require every single fault on Earth to rupture at the same time.



And that would be bad, right?


Very droll.
It is also an impossible situation. There would be no way that the strain could build up in all the faults at the same time - one fault would rupture before we could ever get to that state. After all, the 1960 Chilean quake ruptured the fault running the entire length of the coast of South America.

Talking about seismic activity, a good question to ask might be "What is the least seismically active country in the world?"

Also, on the subject of measurement scales, another nice little question you could throw the panel is this - can an earthquake have a negative value on the Moment Magnitude Scale?
Answers to both will be forthcoming soon.

P.S. On an additional note, why is it that when I try to quote multiple comments, it never works properly - can somebody tell me why?

[Edit] Thanks Moosh - I hadn't noticed that the BBCode box was ticked. That seems to have sorted out the problem now.


Last edited by brunel on Tue Feb 02, 2010 2:58 pm; edited 1 time in total

 
Moosh
665328.  Tue Feb 02, 2010 1:46 pm Reply with quote

brunel wrote:
crissdee wrote:
brunel wrote:
......around 10.5 on the Mw scale, which would require every single fault on Earth to rupture at the same time.



And that would be bad, right?


P.S. On an additional note, why is it that when I try to quote multiple comments, it never works properly - can somebody tell me why?

I have no idea. Unless you have disabled BBCode in your posts. Seems to work fine when I quote your post.

 
brunel
666598.  Thu Feb 04, 2010 4:25 pm Reply with quote

Hmm, since nobody evidently has tried answering my questions, I might as well put up the answers.
Firstly, the least seismically active country is said to be Ireland, where there is so little seismic action that it is effectively considered inactive by seismologists.
As for whether there can be earthquakes with negative values on the MMS scale, the answer is yes. Due to the fact that the MMS scale is logarithmic, you could theoretically have values extending to minus infinity.
In practise, however, most engineers wouldn't bother with anything below Mw = 4.5 (which, based on empirical data, is when structural damage would start to occur for buildings designed without seismic activity taken into account). Meanwhile, the limit for human perception is usually Mw = 3.0, which is about the same as what you'd feel if you were standing by the side of the road, and a heavily laden truck went past you.

On another note, here is an alternative question - recently, legal proceeding have started against Markus Häring, started by Basle local government officials, for causing an earthquake.
The question is how and why did he cause an earthquake?

 
thedrew
666630.  Thu Feb 04, 2010 5:28 pm Reply with quote

The press still speak in Richter Scale "equivalents." The Scale doesn't have an upper limit, but for social purposes "10.0" is used in reference to the supposed "Big One" that is to occur on the San Andreas Fault any minute now. As the scale is no longer used outside of the press, and nothing above 10.0 has ever been recorded on that scale, one may as well consider 10.0 as the upper limit.

 
brunel
666763.  Fri Feb 05, 2010 6:20 am Reply with quote

thedrew wrote:
The press still speak in Richter Scale "equivalents." The Scale doesn't have an upper limit, but for social purposes "10.0" is used in reference to the supposed "Big One" that is to occur on the San Andreas Fault any minute now. As the scale is no longer used outside of the press, and nothing above 10.0 has ever been recorded on that scale, one may as well consider 10.0 as the upper limit.


Why they use "10.0" for the San Andreas fault is surprising - as far as I know, the maximum credible earthquake for the San Andreas fault is probably around magnitude 8.5-9.0. Equally, since it is quite an active fault, given that two moderately large earthquakes have been recorded recently (1989 Loma Prieta, magnitude 7.1, and 2004 Parkfield, magnitude 6.0), the stoed strain energy in the fault would probably be insufficient to cause such a massive earthquake.
I'll have to check the numbers, but my gut feeling is that the San Andreas fault would be too short to store enough energy to much exceed magnitude 9.0.

Regardless, though, whatever scale is used, since they are all logarithmic, all practical earthquake scales would, although potentially extending to an infinitely large event, will have a practical limit of about 10.0-10.5.

 
VaultAir
676035.  Fri Feb 26, 2010 5:08 am Reply with quote

brunel wrote:
On another note, here is an alternative question - recently, legal proceeding have started against Markus Häring, started by Basle local government officials, for causing an earthquake.
The question is how and why did he cause an earthquake?


A $60 million project to extract renewable energy from the hot bedrock deep beneath Basel, Switzerland, was shut down permanently on Thursday after a government study determined that earthquakes generated by the project were likely to do millions of dollars in damage each year. Essentially, drilling so deep into the earth's core has serious potential to generate earthquakes and in Basel, it appears that it did.

The earthquakes didn't actually kill or injure anyone but caused over 9 million dollars worth of damage. The problem is, I suppose, is that it doesn't do geothermal's prospects as a clean renewable source of energy any good. Even though the earthquakes haven't killed anyone....few politicians are going to jump behind it and say, well lets try it anyhoo. That would be a "courageous" decision, would it not, Sir Appleby?

sources:

http://greenenergyreporter.com/2009/12/geothermal-project-shut-down-because-of-quake-threat/#more-4943post

 
Jenny
676191.  Fri Feb 26, 2010 10:43 am Reply with quote

VaultAir wrote:
That would be a "courageous" decision, would it not, Sir Appleby?


Sir Humphrey, please!

 
zomgmouse
676193.  Fri Feb 26, 2010 10:49 am Reply with quote

Do any go up to 11?

 

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