Clough
Feb 10, 2010, 08:52 PM
Hi, All!

Would someone knowledgeable please describe to me, in layman's terms, how the magnitude of earthquakes is determined, please?

I'm not a mathematician nor a geologist, so putting things in terms of logarithms means nothing to me.

Of concern are the following:

Illinois earthquake: How bad is a 3.8 magnitude? / The Christian Science Monitor - CSMonitor.com (http://www.csmonitor.com/Innovation/2010/0210/Illinois-earthquake-How-bad-is-a-3.8-magnitude)

Mild earthquake rattles Chicago area - Chicago Breaking News (http://www.chicagobreakingnews.com/2010/02/quake-like-tremors-reported-in-western-suburbs.html)

I live in Illinois and of course, what happened in Haiti, is a great concern!

Thanks!

KISS
Feb 10, 2010, 09:17 PM
Does this help?

Richter magnitude scale - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Richter_magnitude_scale)

In terms of the scale. Whole numbers are powers of 10.
Comparing a 2 to a 3 or a 3 to a 4 means 1 power of 10 or 10x.

Comparing a 5 to a 1 means 4 powers of 10 or 10*10*10*10

So a 5 is 10000x more powerfull than a 1.

Clough
Feb 10, 2010, 09:30 PM
It's still way over my head, KISS!

I'm a simple person...

Please remember, that I don't really know, nor can I understand the mathematics of it.

Please try to teach me, as though I am a child.

Thanks!

KISS
Feb 10, 2010, 09:41 PM
OK, let's go to music for a bit. Say a piano or guitar.

The harder you hit a key on the piano, the louder the note, however if you hit twice as hard, it's not twice as loud. Hearing also has a log scale to it. That's the concept.

The string of the piano is like the amplitude of the seismometer. An initial impulse with a decay.

Have you ever owned a stereo or professional recording equipment that had a volume control labeled from -infinity to 0.
0 is fully clockwise.

Clough
Feb 10, 2010, 09:44 PM

Let's pretend that I really am a child...

Thanks!

KISS
Feb 10, 2010, 10:37 PM
Log10(10) = 1, log10(100)=2, log10(1000)=3, log10(10,000)=4; log10(100,000) = 5

10^0 =10; 10^2 =100; 10^3 = 1000; 10^4 = 10,000

Note, that the logarithm base 10 of those particular numbers is just the exponent.

LOG10 is pronounced the logarithm base 10.

In this plot; log10(x); x=1 to 100000 - Wolfram|Alpha (http://www33.wolframalpha.com/input/?i=log10%28x%29%3B+x%3D1+to+100000) note how BIG numbers are converted to relatively small numbers.

Clough
Feb 10, 2010, 10:43 PM
What you're writing is still not helping me.

Please remember to teach me as though I am a child that has no knowledge of advanced mathematics.

Thanks!

KISS
Feb 10, 2010, 11:13 PM
Did you click on the log10(x);... LINK above?

Clough
Feb 10, 2010, 11:27 PM
Yes, I did click on the link and go to it.

It's all a bunch of "Greek" to me!

Have you ever been a teacher, please!

Thanks!

KISS
Feb 11, 2010, 08:13 AM
OK, let's try again. You know how to divide by 10, right?

So, very simply take the following numbers: 10, 100, 1000, 10,000 and divide each by 10 and you get the results of 1,2,3, and 4.

I can re-create the number if I know the base, which is 10.

So, for the number 1, I multiply one 10 and get 10
For the number 2, I multiply 10 * 10 and get 100
Fir the number 3, I multiply 10 * 10 * 10 and get 1000

That's the basics.

FlyYakker
Mar 21, 2010, 04:49 PM
Oops, I'm late to the party. Well, for posterity.

Consider the number 10.

If 10X10=100, the base number is 10. The logarithm of 100 using 10 as the basis (or "base") is 2 (note the two 10s). For convenience, it is conventional to write this as log10(100)=2

10X10X10=1000 The base number is still 10 (and note that there are three of them. The logarithm of 1000 using 10 as the base is 3,
Or log10(1000)=3

10x10x10x10=10,000, that is, the logarithm of 10,000 using 10 as the base is 4, or log10(10,000)=4

Now, the base does not have to be 10, It could be, say, 2.

2x2x2=8: The log2(8)=3 That is, the logarithms to base 2 of 8 is 3.

Nor does the log have to be a whole number. It could be (and in practical use, usually is) a decimal fraction, e.g., .5, .8, 2.73, 8.294756..... I am not nearly smart enough to calculate any results using a fractional logarithm, but there are tables of logarithms to various bases available that let you look up the results.

Notice how much and how fast the calculated result increases as we increase the logorithm. You may have heard the term"exponent". Logorithms are sometimes called "exponents" and the rapid rise in the calculated value associated with this kind of calculation is called "increasing exponentially". This shows why a small increase on the Richter scale...which is logorithmic.... Can mean a large difference in the energy of the earthquake being measured.

Clough
Mar 21, 2010, 08:52 PM
So, are logarithms all based on the number 10, FlyYakker!

Thanks!

KISS
Mar 21, 2010, 09:31 PM
No, only base 10 logarithms are based on the number 10.

In fact there is the natural log which is based on the irrational number e which is aproximately = to 2.718281828.. PI is an irrational number too which is ~2.1415926...

FlyYakker
Mar 24, 2010, 05:30 PM
KISS is correct. As I noted, the log of 8 using a base of 2 is 3.

The log of 4 to base 2 is 2.

I'm not trying to overly complicate it but trying to clarify for you why the "base" is specified - simply because other bases are possible depending on what you are trying to do. Log3(9)=2

The natural log KISS points to comes up relatively often in more technical calculations. That aside, most (maybe all?)log tables you will see are for base 10.

Just worry about base 10. The principal is really all you want to know about and base 10 is as good as any other for understanding the principal.

Clough
Mar 24, 2010, 09:42 PM
So, what's an irrational number, please?

I'm clueless! :confused:

Maybe I'm too old for the math stuff...

That possible?

KISS
Mar 24, 2010, 09:56 PM
Irrational number: A number that cannnot be written as a ratio of two integers. PI is one. You know area of circle = PI*R^2.

firmbeliever
Mar 25, 2010, 03:57 AM
These might help explain it a little, I couldn't watch all the videos due a net connection problem.Let me know if it helps.

YouTube - How Things Work : How Does the Richter Scale Work? (http://www.youtube.com/watch?v=wVqYg4NPvC4&feature=related)

Also, this seems simpler as an explanation.Not that I understand all of it.
How do scientists measure earthquakes? (http://tremor.nmt.edu/faq/how.html)

EDIT:
These help a bit more.
http://earthquake.usgs.gov/learn/faq/?faqID=111
http://earthquake.usgs.gov/learn/faq/?categoryID=2&faqID=118/index.html

.

Clough
Mar 25, 2010, 11:31 AM
Very helpful videos and information, firmy!

Thanks!

firmbeliever
Mar 25, 2010, 11:36 AM
Welcome!:)

I understand what you meant layman terms as I am a person who tries to look for the simplest explanation too, as I don't understand many of the mathematical terms.

.

Clough
Mar 25, 2010, 11:49 AM
Noted and I admire the way that you care and try to be as helpful as you can, firmy!

Would someone please explain to me what a "log" is concerning mathematics?

I'll get these things if you teach me, but if you don't teach me in the simplest terms, I ain't going to get it!

Here's the chance for some of you to be teachers!

If you would like to learn about music starting on the first step, I'll be glad to teach you!