1. earthquak
es and how
do they
occur?
Chapter 5: Lesson 3:

2. What is an
It is the sudden
earthquake?
movement of
earth’s crust.

3. When layers
of rock that
are stuck
together
suddenly slip
an
earthquake

4. When two
plates slide
past each
other, they
create a
transform
fault, like

5. Slipping along a fault
begins under the earth’s
surface.
(80 km – 644 km deep)
The place where the
slipping begins is called

7. Waves of energy ripple
outwards from the focus.
When the waves reach the surface

8. The epicenter is the point from
where the waves of the
earthquake spread.
(People start feeling the
earthquake)

9. Earthquakes occur at plate
boundaries
(like volcanoes)

10. Seismometers
Instruments used to measure the
waves produces by an
earthquake.

11. There are 3 types of seismic
waves
P waves
(Primary
waves)
S waves
(Secondary
waves)
Lg waves
(Surface
waves)

12. P waves
- Move back and forth
- Fastest
- Travels through solid and
liquid layers of earth.

13. S waves
- Moves up and down.
- Travel half as fast as P waves.
- Travels through solid layers
of earth only.

14. Lg waves
- Travels as ripples across
earth’s surface.
- Slowest.
- Causes most damage.

15. Lg waves
P waves
S waves

16. Locating earthquakes
Earthquake
epicenter can
happen any where
along
circumference
Seismometer
station 1

17. The point where the 3
circles meet is the
epicenter
Seismometer
station 1
Seismometer
station 2
Seismometer
station 3

18. Magnitude
The measure of the amount of
energy released by an
earthquake.
Richter scale
Mercalli
scale

19. Richter scale
Measures the magnitude at
the epicenter
(From weakest to
strongest)
The Richter scale starts from 1 and each whole number
has 30 times more energy than the number before it.

20. Mercalli
scale
Measures what people felt
and what happens to things
in a place
On the mercalli scale earthquakes are rated from I – XII
(XII is the most severe)

21. Mercalli scale

22. The earthquake in Pakistan
on October 8, 2005 was rated
XII the mercalli scale.

23. Aftershock
Earthquakes with lesser
magnitude.
(Felt after the main
earthquake)
Earthquakes with larger magnitudes have many
aftershocks with large magnitudes.

24. When earthquakes occur on
the ocean floor waves of
water are pushed upwards
in sea the
Deep in the all directions.
energy is spread
through the water
so the waves are
not tall.

25. When the waves reach
shallow water the energy
is spread through less
water.
In shallow waters
the waves are
very tall causing
tsunamis.