# The Naked Scientists Forum

### Author Topic: Earth tremor in the UK  (Read 14811 times)

#### another_someone

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##### Earth tremor in the UK
« Reply #25 on: 01/03/2008 21:04:26 »
OK  looking at wiki, it seems both sides are right.

http://en.wikipedia.org/wiki/Richter_magnitude_scale
Quote
The Richter magnitude scale, or more correctly local magnitude ML scale, assigns a single number to quantify the amount of seismic energy released by an earthquake. It is a base-10 logarithmic scale obtained by calculating the logarithm of the combined horizontal amplitude of the largest displacement from zero on a Wood-Anderson torsion seismometer output. The effective limit of measurement for local magnitude is about ML=6.8. The energy release of an earthquake scales with the 3/2 power of the shaking amplitude, and thus a difference in magnitude of 1.0 is equivalent to a factor of 31.6 in the energy released; a difference of magnitude of 2.0 is equivalent to a factor of 1000 in the energy released.

The Richter magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded by seismographs (adjustments are included to compensate for the variation in the distance between the various seismographs and the epicenter of the earthquake). Because of the logarithmic basis of the scale, each whole number increase in magnitude represents a tenfold increase in measured amplitude; in terms of energy, each whole number increase corresponds to an increase of about 31.6 times the amount of energy released.

So a whole number increase is a factor of 10 increase in wave amplitude, but a factor of 31.6 increase in energy.

I should have read that first - sorry.
« Last Edit: 01/03/2008 21:06:23 by another_someone »

#### JimBob

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##### Earth tremor in the UK
« Reply #26 on: 01/03/2008 21:13:18 »
Then don't tell him! Jees, I can't believe a woman can't be even have a little smidgen of deviousness.

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##### Earth tremor in the UK
« Reply #27 on: 01/03/2008 21:56:32 »
Husband still smug but not gloating anymore. It is nice when we are both right. Anyone got anything to add on this?

#### Exodus

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##### Earth tremor in the UK
« Reply #28 on: 02/03/2008 15:02:29 »
Basically as is said in geography... a hazard only becomes a hazard when people locate themselves in its area... And whoever said that a 5 is not a big quake is wrong... If you look at the Richter scale graphically it is a base 10 logarithmic scale which means that each quake number is 10 times more powerful than the last... these means that a magnitude 5 is 100000 more powerful than a 1!

#### Bored chemist

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##### Earth tremor in the UK
« Reply #29 on: 02/03/2008 15:30:34 »
"these means that a magnitude 5 is 100000 more powerful than a 1"
Er, no it doesn't. Each quake number has 10 times the amplitude of the one below not 10 time the power. I'm guessing the the velocity of the wave is prety much independdent of the released energy. That means that a change of 1 unit gives 10 times the apmlitude and so takes roughly 10 times as long. But it dissipates 31.6 times as much energy in that time so it has about 3.16 times more power. A magnitude 5 quake would be about 316 times the power but I don't know how that relates to how much damage is done.

#### Exodus

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##### Earth tremor in the UK
« Reply #30 on: 02/03/2008 17:18:23 »
"these means that a magnitude 5 is 100000 more powerful than a 1"
Er, no it doesn't. Each quake number has 10 times the amplitude of the one below not 10 time the power. I'm guessing the the velocity of the wave is prety much independdent of the released energy. That means that a change of 1 unit gives 10 times the apmlitude and so takes roughly 10 times as long. But it dissipates 31.6 times as much energy in that time so it has about 3.16 times more power. A magnitude 5 quake would be about 316 times the power but I don't know how that relates to how much damage is done.

Indeed you are correct :-) gold star for you, detention for me. Walks away in shame.

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##### Earth tremor in the UK
« Reply #31 on: 02/03/2008 22:13:13 »
I like your answer Bored C but I hope you don't gloat as much as hubby. Be humble in your glory.
Exodus, I just heard they have invented Sat Navs for zimmer frames so when senility takes over completely at least you can find your way home.

#### Exodus

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##### Earth tremor in the UK
« Reply #32 on: 02/03/2008 22:40:47 »
I like your answer Bored C but I hope you don't gloat as much as hubby. Be humble in your glory.
Exodus, I just heard they have invented Sat Navs for zimmer frames so when senility takes over completely at least you can find your way home.

Its not senility today, its a hangover. lol

#### JimBob

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##### Earth tremor in the UK
« Reply #33 on: 03/03/2008 03:14:14 »
I like your answer Bored C but I hope you don't gloat as much as hubby. Be humble in your glory.
Exodus, I just heard they have invented Sat Navs for zimmer frames so when senility takes over completely at least you can find your way home.

Why didn't you just say "walker" instead of zimmer frame? We Americans do not know what a bonnet is, a turtle or that both relate to a auto. That is all but I don't know.

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##### Earth tremor in the UK
« Reply #34 on: 03/03/2008 13:48:05 »
Which bit of a car is a turtle? I know you Americans drive slowly but turtles! Oh yes and on Docs behalf shouldn't it be an Auto. Anyway we are supposed to be talking about Earthquakes so lets take this outside.

#### The Naked Scientists Forum

##### Earth tremor in the UK
« Reply #34 on: 03/03/2008 13:48:05 »