1. Earthquakes are caused by movements in the Earth's crust along fault lines and plate boundaries. The most severe earthquakes typically occur at destructive and conservative plate boundaries. 2. Scientists can measure earthquakes using seismographs, which detect seismic waves. The Richter scale is used to quantify the magnitude or strength of an earthquake based on the seismograph recording. 3. In addition to the Richter scale, the Mercalli scale is used to describe the intensity or amount of damage caused by an earthquake based on observations of its effects.

1. Earthquakes…

2. What are earthquakes and where do they occur?
Earthquakes are
DESTRUCTIVE vibrations caused by
earth movements at plate
boundaries and at major
fault lines (cracks in the
earth’s surface).
CONSERVATIVE They can occur at all 4
major plate boundaries
but the most severe
earthquakes are normally
found at CONSERVATIVE
and DESTRUCTIVE
boundaries.

3. Why do earthquakes happen?

4. Epicentre and focus

5. Epicentre and focus
Focus
Epicentre
An earthquake has occurred along this fault line.
Match the letter with the correct label.

6. Epicentre and focus
An earthquake has occurred in this area.
Which area (the town or the forest) will receive the stronger
earthquake?
Which area will receive more damage from the earthquake?

7. A seismograph

8. How can we measure earthquakes?
The Richter Scale
1
This measures the magnitude of a 2
tremor (how powerful it is) using an 3
4
instrument called a seismograph. 5
6
On the Richter Scale, magnitude is 7
8
expressed in whole numbers and 9
decimal fractions. Although the 10
Richter Scale has no upper limit, the Richter
largest known shocks have had Scale
magnitudes in the 8.8 to 8.9 range. It
is a logarithmic scale which means The largest earthquake
ever recorded was in
that a size ‘6’ on the Richter Scale is
Chile. It measured 9.5
10 times larger than a size ’5’ and on the Richter Scale.
100 times larger than a size ‘4’.

9. • http://www.iris.edu/seismon/
• http://www.earthquakes.bgs.ac.uk/recent_
events/recent_events.html

10. Why do we get earthquakes in Britain?
• We actually have 50-60 small earthquakes every year!
• These occur along ‘fault lines’ (cracks in the main plates deep
beneath the ground).
• As our plate is moving very slowly to the east every now and
then there are small movements along faults.
• The most Britain can expect to see, in terms of damage, is
chimney pots falling down and windows cracking.
Why don’t we ever get BIG earthquakes?
Because we are not near a plate boundary but inside the
Eurasian plate.

11. How can we measure earthquakes?
The Japanese earthquake in Kobe
1
(September 1995) measured 7.2 on the 2
Richter Scale. 3
4
5
6
The Greek earthquake (June 1995) 7
8
measured 6.2 on the Richter Scale. 9
10
Richter
Scale
How many times greater was the Japanese earthquake?

12. Mercalli Scale
This measures
how much
damage is
caused by the
earthquake
Mercalli Scale
based on
observations. It
is measured on a
scale between I
and XII.

13. Activity
Design your own cartoon based on the Mercalli Scale
descriptions below.
I Felt by almost no one.
II Felt by very few people.
III Tremor noticed by many, but they often do not realise it is an
earthquake.
IV Felt indoors by many. Feels like a truck has struck the building.
V Felt by everyone; many people are awakened. Swaying trees and
poles may be observed.
VI Felt by all; many people run outdoors. Furniture is moved.
VII Everyone runs outdoors. Poorly built structures considerably
damaged. Slight damage elsewhere.
VII Specially designed structures damaged slightly, others collapsed.
IX All buildings considerably damaged, many shift off foundations.
Noticeable cracks in the ground.
X Many structures destroyed. Ground badly cracked.
XI Almost all structures fall. Bridges wrecked.
XII Total destruction. Waves seen on ground surfaces, objects are
tumbled and tossed.

14. Your task:
1. In your own words, explain why earthquakes happen
(include a diagram). What type of plate boundary are
they mainly found at?
2. What are the focus and epicentre? Draw a diagram to
illustrate this.
3. What are seismic waves?
4. What instrument do scientists use to measure the
strength and duration of an earthquake? Explain how it
works.
5. What is the richter scale?
6. What was the largest earthquake ever recorded?
Where was it?

15. How can we limit earthquake damage?
predict plan protect
water levels can rise in
a tiltmeter can check any wells and lakes because
movement within the rocks of cracks in the rock
1. predict
animals can act
foreshocks before the main strangely before the
quake can be detected by a earthquake
seismometer

16. How can we limit earthquake damage?
advise people to plan for an
earthquake (eg tell them to
turn off the gas, find a ‘safe’
place in their homes, pack make an emergency plan
an emergency kit)
2. plan
enforce regulations to organize regular
make some buildings ‘earthquake practices’
earthquake proof for offices and schools
What should people pack in their emergency kit?
Design a poster reminding people what to do in an earthquake.

17. DROP COVER HOLD-ON…
• http://news.bbc.co.uk/1/hi/world/americas/
7726924.stm
http://www.youtube.com/watch?
v=j8mUZFeMwhE
http://www.youtube.com/watch?
v=bAHNhtRT50A earthquake drill at
school
• http://news.bbc.co.uk/1/hi/world/americas/
7726031.stm simulation

18. This is San Francisco in the USA.
Why does this skyscraper have a wide base?

19. Building regulations in earthquake zones
overlapping bricks
strong lintels
deep foundations
What other measures would make buildings less likely to
collapse in an earthquake?

20. Which shape of building would be most ‘earthquake proof’?

21. Sky’s the limit!
This is the Sky Tower in Auckland, New
Zealand.
Sky Tower is the tallest tower in the Southern
Hemisphere and the twelfth tallest in the World.
Sky Tower is 328 metres tall (more than 1,076
feet); that's about 37 buses standing end on
end!
Sky Tower weighs 21 million kilos (20,000
tonnes) which is equivalent to 6,000 elephants.
Problem – Auckland is in an earthquake zone.
How could you make buildings such as the Sky Tower
more ‘earthquake proof’?

22. What they did…
Sky Tower is constructed from a high strength, high
performance concrete.
The main structure of Sky Tower is a reinforced concrete
shaft measuring 12 metres in diameter. It is supported by
eight reinforced concrete 'legs' at the base, connected to
the shaft by a concrete collar and designed to spread force
load.
Sky Tower's foundations go down more than 15 metres.
The tower was tested to see if it would withstand
earthquakes. Analysis shows that an earthquake
measuring 7.0 on the Richter scale, located 40 kilometres
from Sky Tower on the Kerepehi Fault, would leave Sky
Tower essentially undamaged. In the extreme event of a
magnitude 8.0 earthquake occurring within 20 kilometres of
the tower, analysis shows that Sky Tower would remain
standing.

23. Your task…
7. How can we limit earthquake damage? Mention ways of
predicting, planning and protecting.
8. What is the best shape for a building in an earthquake
zone? Draw a diagram. What other measures can be
taken to protect a building?
9. What should people do in an earthquake? Design a
poster to be put up in public buildings, informing
people what they should do.
10. What’s the Mercalli scale? Divide a page into 12 boxes
and illustrate the twelve stages.