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Did you know…?
… that there are aproximately 6000 earthquakes every
year in the world? Only a few are powerful enough to
cause significant damage.
What happens in an earthquake?What happens in an earthquake?
The most violent earthquakes occur near the
plate boundaries. The plates often stick together
and then suddenly jolt appart, causing an
What causes earthquakes?What causes earthquakes?
The place underground
where the rock breaks is
known the focus. The
place at the surface,
directly above the focus, is
called the epicentre.
Seismic waves ripple
outwards from the
epicentre in all directions.
Tectonic plates are locked together by friction
Pressure builds up due to movement in the mantle
The rock breaks along a weak point (fault line)
The tectonic plates suddenly move
Stored energy is released as seismic waves
The Earth’s surface shakes
Impact of earthquakesImpact of earthquakes
• Structural damage Primary effects: hazards right
• Falling objects after an earthquake strikes
• Tsunamis Secondary effects: problems hours/
• Disease days after earthquake
Recording earthquakesRecording earthquakes
Earthquakes are recorded
using very sensitive
The vibrations they detect
are drawn on a seismograph.
The print out tells us how
powerful the earthquake was
and how long it lasted.
How do we measure an earthquake?How do we measure an earthquake?
We use the Richter Scale to
measure the total amount of
energy released in the
It tells us how strong it
was - 1 being weak and 10
being absolute devastation.