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Earthquakes in
British Columbia
Earthquake Magnitude - The Richter Scale
The strength of an earthquake can
also be measured and expressed in terms of the
magnitude of energy released by the earthquake.
Seismologist Charles Richter
devised his system based on the amplitude of the
seismic waves recorded by seismographs. When the
data from several seismometers are compared a
measure of magnitude can be realized within
minutes of the earthquake activity.
The Richter scale is logarithmic.
An increase in magnitude of one unit corresponds
to a tenfold increase in the size of an
earthquake. Thus an earthquake of magnitude 6 is
ten times larger than one of magnitude 5, and a
hundred times larger than one of magnitude 4.
Richter Scale
Richter
Scale # |
Earthquakes
globally per year |
Typical
Intensity at center
(see Mercalli Scale) |
Acceleration.
% of gravity (g) |
| 8.0 + |
0.1 - 0.2 |
XII |
- |
| 7.4 - 8.0 |
4 |
XI |
- |
| 7.0 - 7.3 |
15 |
X |
70 |
| 6.2 - 6.9 |
100 |
VIII - IX |
15 - 32 |
| 5.5 - 6.1 |
500 |
VII |
7 |
| 4.9 - 5.4 |
1,400 |
VI |
3 |
| 4.3 - 4.8 |
4,800 |
IV-V |
0.7-1.5 |
| 3.5 - 4.2 |
30,000 |
II - III |
0.2 - 0.3 |
| 2.0 - 3.4 |
800,000 |
I - II |
0.1 - 0.2 |
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