What is the Richter Scale?
The Richter Scale
Grade 12
Advanced Mathematics
• Rates the magnitude
of an earthquake
– The energy released
during the quake
• It is a logarithmic
scale
– Coverts multiplication
expressions to
addition expressions
y = log x
-2 = log 0.01
-1 = log 0.1
0 = log 1
1 = log 10
2 = log 100
What is a Log Scale?
• An earthquake measuring a 5 on the Richter Scale
is TEN times as large as an earthquake that
measures 4 on the Richter scale
• Charles F. Richter defined the magnitude, R, of an
earthquake as:
I 
R = log10  
 I0 
The Formula
I 
R = log10  
 I0 
R represents the measure on the Richter
Scale
I represents the intensity of the earthquake
I0 is the intensity of the reference earthquake
(we say that I0 is equal to 1 micron)
1
Recent Earthquakes
Date
Location
Magnitude
April 12
Baja California,
Mexico
3.4
April 12
Kuril Islands
4.6
April 12
Honshu, Japan
4.8
April 12
Honshu, Japan
4.9
April 12
Honshu, Japan
6.0
Question 1
Question 2
How much more intense is an earthquake of
Magnitude 6.2 on the Richter scale than one
that measures 5.7?
How much more intense is an earthquake of
Magnitude 7.4 on the Richter scale than one
that measures 4.3?
2
Question 3
What is the intensity in microns of an
earthquake that registers as 7.2 on the
Richter Scale?
Question 5
If one earthquake measures 5.7 on the
Richter Scale and a second earthquake is
10 times as intense, what would the
magnitude of the second earthquake be?
Question 4
What is the intensity in microns of an
earthquake that registers as 8.9 on the
Richter Scale?
Question 6
If one earthquake measures 4.9 on the
Richter scale and a second earthquake is
100 times as intense, what would the
magnitude of the second earthquake be?
3
Question 7
An earthquake measuring 6.6 on the Richter
Scale occurred in Eastern Honshu, Japan
on April 11. An earthquake measuring 5.9
on the Richter Scale occurred in the Bonin
Islands, Japan Region on April 10. How
many times less intense was the earthquake
in the Bonin Islands?
4