Page 241 - Big Ideas Year 10 sciPAD 2025

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SCIPAD - BIG IDEAS - BOOK 2
EARTH SYSTEMS
Events at Plate Boundaries - Earthquakes
Earthquakes occur when two or more tectonic plates move against each other. The Pacific Plate is
moving towards New Zealand at a rate of 4-5 cm per year. This movement is not smooth or constant
as friction between the two plates prevents constant movement. Therefore, pressure builds up
within the plates. This pressure causes faults (or cracks) within the crust that can rupture, releasing
energy in the form of seismic waves - an earthquake. There are more than 20 000 earthquakes
recorded in New Zealand every year, but only around 300 of these are strong enough to be felt.
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10 New Zealand’s Biggest Earthquakes
8.2 Wairarapa (1955). Most severe
earthquake in New Zealand’s
recorded history. Fewer than 10
deaths.
7.8 Fiordland (2009). Permanently moved
the South Island 30 cm closer to
Australia. No fatalities and virtually no
damage to buildings.
7.8 Napier (1931). Largest loss of life of any
New Zealand earthquake with 258
fatalities.
7.8 Murchison (1929). Caused massive
landslides. Widely felt. 17 deaths.
7.8 Kaikoura (2016). 2 deaths. One of
the most complex earthquakes ever
studied.
7.2 Wairarapa (1942). Extensive damage
to buildings. No fatalities.
7.1 Inangahua (1968). Felt from Whangarei
to Invercargill. 3 deaths and extensive
landslides and damage to buildings.
7.1 Christchurch (2010). Widespread
damage and several power outages.
No fatalities.
6.3 Christchurch (2011). Severe and
widespread damage to thousands of
buildings. Liquefaction. 182 fatalities.
Anatomy of an Earthquake
Epicentre: Area of land
directly above the focus.
Focus: The origin of the
earthquake. Where the
pressure is released.
Fault: Movement
occurs along
cracks in the earth.
Liquefaction: Loose,
wet soil may ‘liquefy’.
Seismic waves: Vertical
and horizontal waves of
energy.
Felt only nearby,
if at all.
Equivalent to 1.5
Hiroshima atom
bombs.
Equivalent to 30
tonnes of TNT.
Often felt up to 10’s
of kilometres away
from the source.
Equivalent to 1
million tonnes of TNT
Can be destructive
in areas where
people live up
to abound 100
kilometres across.
Major earthquake.
Can cause serious
damage over
large areas.
Equivalent to 30
billion tonnes of
TNT. Can cause
serious damage
in areas 100’s of
kilometres across.
Never
experienced.
Equivalent to
14kg of TNT.
Richter Scale
1. Outline why earthquakes occur. 

2. Explain what prevents tectonic plates from moving in a smooth, constant manner.

3. Define the term ‘fault’. 
4. As a percentage, how many earthquakes are large enough to be felt in New
Zealand every year? 
5. Explain the difference between an earthquake’s focus and its epicentre. 


6. What happens to wet, loose soil during an earthquake? 
7. Suggest a reason why the 2009 Fiordland earthquake did so little damage to
buildings and people. 

8. What level on the Richter scale is equivalent to the energy released by 1 million
tonnes of TNT exploding? 
9. (a) Where was New Zealand’s deadliest earthquake? 
(b) On the Richter scale, what was the magnitude of this quake? 
9.5 - Chile
(1960). Largest
recorded
earthquake.