Formula for *I* vs. m

With mathematics which we won’t derive here, you
can show this is equivalent to the equation:

This
second equation is easy to use on a calculator.

If you remember that log( 10n ) = n, for example

log( 104) = 4, log (105) = 5, log(106) = 6,

you can use it even without a calculator.

If you remember that log( 10n ) = n, for example

log( 104) = 4, log (105) = 5, log(106) = 6,

you can use it even without a calculator.

Intensity
Ratio

Magnitude Difference

10,000,000,000

25

...

...

1,000,000

15

...

...

10,000

10

4,000

9

1,600

8

630

7

250

6

100

5

40

4

16

3

6.3

2

2.5

1

1

0