1. TECTONIC LANDSCAPES
MEASURING MAGNITUDE

2. SPECIFICATION DETAIL
• 3.1d The measurement of earthquake magnitude
(the Mercalli and Richter scales).
• Diagrams showing the characteristics of focus and
epicentre.

3. LEARNING OBJETIVES
• Know the differences between the
Mercalli (intensity) and Richter
(magnitude) scales.
• Explain how earthquakes occur with
reference to the epicentre and focus
of earthquakes.

4. DEFINITIONS
• Watch Seismograph: Here
• Mercalli scale: (intensity)
Uses seismic scale to measure the intensity of an earthquake. It is
used to measure the effects of an earthquake.
• Richter scale: (magnitude)
A logarithmic scale used to express the total amount of energy
released by an earthquake
(It is a base 10 logrimithic scale: e.g. 5.0 on the Richter scale has a
shaking amplitude 10 times larger than one that measures 4.0, )
assign a single number to quantify the energy released during an
earthquake.

5. HOW ARE EARTHQUAKES
MEASURED?
The Richter scale can be
used to measure the
magnitude (power) of a
tremor using an
instrument called a
seismograph.
It is a logarithmic scale
which means that a size
‘6’ earthquake on the
Richter scale is 10 times
larger than a size ‘5’ and
100 times larger than a
size ‘4’.

6. HOW DOES A SEISMOGRAPH
WORK?

7. THE MERCALLI
SCALE
The Mercalli scale rates an earthquake's magnitude
based on observations of the damage it causes on a
scale of 1 to 12.
Items shake from Buildings collapse:
shelves: scale 5 scale 10

8. Richter Scale
Intensity Magnitude
Observations (Mercalli)
(Mercalli) (approx.
comparison)
I No effect 1 to 2
II Noticed only by sensitive people 2 to 3
III Resembles vibrations caused by heavy traffic 3 to 4
IV Felt by people walking; rocking of free standing objects 4
V Sleepers awakened; bells ring 4 to 5
VI Trees sway, some damage from falling objects 5 to 6
VII General alarm, cracking of walls 6
VIII Chimneys fall and some damage to building 6 to 7
IX Ground crack, houses begin to collapse, pipes break 7
X Ground badly cracked, many buildings destroyed. Some landslides 7 to 8
XI Few buildings remain standing, bridges destroyed. 8
XII Total destruction; objects thrown in air, shaking and distortion of ground 8 or greater

9. TASK: SORTING
• Using the
following
statements,
sort them
into which
best
describes
the scales.
• Here

10. Richter Scale
Intensity Magnitude
Observations (Mercalli)
(Mercalli) (approx.
comparison)
I No effect 1 to 2
II Noticed only by sensitive people 2 to 3
III Resembles vibrations caused by heavy traffic 3 to 4
IV Felt by people walking; rocking of free standing objects 4
V Sleepers awakened; bells ring 4 to 5
VI Trees sway, some damage from falling objects 5 to 6
VII General alarm, cracking of walls 6
VIII Chimneys fall and some damage to building 6 to 7
IX Ground crack, houses begin to collapse, pipes break 7
X Ground badly cracked, many buildings destroyed. Some landslides 7 to 8
XI Few buildings remain standing, bridges destroyed. 8
XII Total destruction; objects thrown in air, shaking and distortion of ground 8 or greater

11. TASK: WATCH THESE CLIPS
• Tachoma, Japan earthquake: Here
• Chilean earthquake: Here
• Kashima, Japan earthquake: Here
• Tokyo, Japan earthquake: Here
• Maryland, USA earthquake: Here
Which scale was the most easy to use? Why?

12. EXAM PRACTISE
• Describe 2 differences between the Mercalli and
Richter scale. (2 marks)
One difference is …………
A second difference is that……………

13. LEARNING OBJETIVES
• Know the differences between the
Mercalli (intensity) and Richter
(magnitude) scales.
• Explain how earthquakes occur with
reference to the epicentre and focus
of earthquakes.

14. EPICENTRE
• Epicentre on google earth: here
• Interactive : Here

15. EPICENTRE AND FOCUS

16. EXAM QUESTION
• Outline a difference between the focus and
epicentre of an earthquake. (2marks)

17. LEARNING OBJETIVES
• Know the differences between the
Mercalli (intensity) and Richter
(magnitude) scales.
• Explain how earthquakes occur with
reference to the epicentre and focus
of earthquakes.