earthquak
es and how
do they
occur?
Chapter 5: Lesson 3:
What is an
It is the sudden
earthquake?
movement of
earth’s crust.
When layers
of rock that
are stuck
together
suddenly slip
an
earthquake
When two
plates slide
past each
other, they
create a
transform
fault, like
Slipping along a fault
begins under the earth’s
surface.
(80 km – 644 km deep)
The place where the
slipping begins is call...
Waves of energy ripple
outwards from the focus.

When the waves reach the surface
The epicenter is the point from
where the waves of the
earthquake spread.
(People start feeling the
earthquake)
Earthquakes occur at plate
boundaries
(like volcanoes)
Seismometers
Instruments used to measure the
waves produces by an
earthquake.
There are 3 types of seismic
waves
P waves
(Primary
waves)

S waves
(Secondary
waves)

Lg waves
(Surface
waves)
P waves
- Move back and forth
- Fastest
- Travels through solid and
liquid layers of earth.
S waves
- Moves up and down.
- Travel half as fast as P waves.
- Travels through solid layers
of earth only.
Lg waves
- Travels as ripples across
earth’s surface.
- Slowest.
- Causes most damage.
Lg waves
P waves

S waves
Locating earthquakes
Earthquake
epicenter can
happen any where
along
circumference

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

Seismometer
station 2

Seismometer
station 3
Magnitude
The measure of the amount of
energy released by an
earthquake.
Richter scale

Mercalli
scale
Richter scale

Measures the magnitude at
the epicenter
(From weakest to
strongest)
The Richter scale starts from 1 and eac...
Mercalli
scale

Measures what people felt
and what happens to things
in a place
On the mercalli scale earthquakes are rate...
Mercalli scale
The earthquake in Pakistan
on October 8, 2005 was rated
XII the mercalli scale.
Aftershock

Earthquakes with lesser
magnitude.
(Felt after the main
earthquake)
Earthquakes with larger magnitudes have ma...
When earthquakes occur on
the ocean floor waves of
water are pushed upwards
in sea the
Deep in the all directions.
energy ...
When the waves reach
shallow water the energy
is spread through less
water.
In shallow waters
the waves are
very tall caus...
Ch.5.less.4.what are earthquakes and how do they occur
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Ch.5.less.4.what are earthquakes and how do they occur

  1. 1. earthquak es and how do they occur? Chapter 5: Lesson 3:
  2. 2. What is an It is the sudden earthquake? movement of earth’s crust.
  3. 3. When layers of rock that are stuck together suddenly slip an earthquake
  4. 4. When two plates slide past each other, they create a transform fault, like
  5. 5. Slipping along a fault begins under the earth’s surface. (80 km – 644 km deep) The place where the slipping begins is called
  6. 6. Waves of energy ripple outwards from the focus. When the waves reach the surface
  7. 7. The epicenter is the point from where the waves of the earthquake spread. (People start feeling the earthquake)
  8. 8. Earthquakes occur at plate boundaries (like volcanoes)
  9. 9. Seismometers Instruments used to measure the waves produces by an earthquake.
  10. 10. There are 3 types of seismic waves P waves (Primary waves) S waves (Secondary waves) Lg waves (Surface waves)
  11. 11. P waves - Move back and forth - Fastest - Travels through solid and liquid layers of earth.
  12. 12. S waves - Moves up and down. - Travel half as fast as P waves. - Travels through solid layers of earth only.
  13. 13. Lg waves - Travels as ripples across earth’s surface. - Slowest. - Causes most damage.
  14. 14. Lg waves P waves S waves
  15. 15. Locating earthquakes Earthquake epicenter can happen any where along circumference Seismometer station 1
  16. 16. The point where the 3 circles meet is the epicenter Seismometer station 1 Seismometer station 2 Seismometer station 3
  17. 17. Magnitude The measure of the amount of energy released by an earthquake. Richter scale Mercalli scale
  18. 18. 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.
  19. 19. 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)
  20. 20. Mercalli scale
  21. 21. The earthquake in Pakistan on October 8, 2005 was rated XII the mercalli scale.
  22. 22. Aftershock Earthquakes with lesser magnitude. (Felt after the main earthquake) Earthquakes with larger magnitudes have many aftershocks with large magnitudes.
  23. 23. 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.
  24. 24. When the waves reach shallow water the energy is spread through less water. In shallow waters the waves are very tall causing tsunamis.
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