A presentation about the causes and effects of earthquakes.

2. • Causes of earthquakes
• Effects of earthquakes

3. Natural cause:
Earthquakes are the result of slow-moving processes
that operate within Earth.
Earth was hot when it formed, and has been cooling
ever since (near the surface, for each km into Earth,
the temperature rises by about 30deg. Celsius).
Earth's cooling causes the portions of Earth to move,
and that movement is what we call an earthquake.

4. Some of the human decisions
that have induced earthquakes:
• Dams and reservoirs:
It's just water, but, water is heavy. Large reservoirs
of water created by dams have a long history of
inducing earthquakes. The 2008 earthquake in
Sichuan, China, that killed nearly 70,000 people
was one of the most devastating in recent
memory, and some scientists think it was triggered
by the construction of the Zipingpu Dam nearby.

5. • Groundwater extraction:
Taking water out of ground, which causes the
water table to drop, can also destabilize an
existing fault.
• Geothermal power plants:
As the geothermal field
operations have ramped up,
seismic activity has increased
there.

6. • Fracking and injection wells:
When waste fracking fluid is injected back
underground into deep wells. The fluid can
seep out and lubricate faults, causing them
to slip more easily.

7. • Skyscrapers:
It is about putting too much pressure on
the soft sedimentary rock below. This
stress is due to all the extra steel and
concrete used to make the
skyscraper solid enough
to withstand earthquakes.

8. The destructive effects of an earthquake
can be classified into primary and
secondary effects.

9. Primary effects:
They are the immediate damage caused by the
quake, such as collapsing buildings, roads and
bridges, which may kill many people. Those
lucky enough to survive can suffer badly from
shock and panic.

10. Secondary effects:
They are the after-effects of the earthquake.
Secondary effects of
earthquakes
Tsunamis
Soil
liquefaction
Fire
Disease and
famine
Landslides

11. • Fire: earthquakes destroy gas pipes and
electric cables, causing fires to spread. Broken
water mains prevent the Fires being
extinguished. Fires spread very quickly in
cities, especially in poor-quality housing areas
where wooden buildings are common.

12. • Tsunamis: an earthquake on the sea floor or
close to the coast may cause huge waves.
• Landslides: earthquakes
often cause landslides,
especially in steep river
valleys and areas of
weak rocks.

13. • Disease and famine: fresh water supplies are
often cut off causing typhoid and cholera. Lack of
shelter and food causes much suffering.
• Soil liquefaction: when
soils with a high water
content are violently
shaken they lose their
mechanical strength and
behave like a fluid and so
buildings can literally sink.