The document discusses earthquakes and how they occur. It explains that earthquakes are caused by sudden movement along faults in the Earth's crust due to a build up of stress. There are three main types of faults - normal, reverse, and strike-slip - each forming in a different way due to tension or compression in the crust. When friction along a fault is overcome, the fault will slip and move, causing seismic waves that produce shaking during an earthquake. The intensity of shaking and damage decreases further from the earthquake's epicenter.

2. 

3. 
Why do we need to learn about
earthquakes?

4. 
The shaking or trembling caused
by the sudden release of energy.
It occur when rocks along a fault
suddenly move.
EARTHQUAKE

5. 
STRESS
-- is a force that squeezes rocks together,
stretches or pulls them apart, or pushes them
in different directions.
*As tectonic plates move, they cause stress in
the crust, which in turn produces faults and
folds.
STRESS IN EARTH’S CRUST

6. 
WHERE DO EARTHQUAKES
OCCUR?

7. 
A fault is a break in the
Earth’s crust along which
significant movement has
taken place.
FAULTS

8. 
FAULTS

9. 
HOW DO FAULTS
PRODUCE
QUAKES??

10. 
THREE TYPES OF
FAULTS

11. 
-- forms as a result of
tension.
*The rock layers in the
Earth’s crust are pulled
apart, and gravity causes
one section to move
downward in relation to
the other.
NORMAL FAULT

12. 
-- forms as a result of
compression.
*The rock layers in the
earth’s crust are
squeezed together, and
the force pushes one
section upward in
relation to the other.
REVERSE FAULT

13. -- forms when the rock
layers on opposite
sides of a fault slides
past each other
horizontally.
*This type of fault is
sometimes called as
tear, wrench or
transcurrent fault.
STRIKE-SLIP FAULT

14. 
ENERGY from inside the Earth make the ground
move. There is no movement friction right away
because of the FRICTION. Friction held the rocks
together. Once the friction is overcome, the ground
will move and the earthquake will occur.
Every time a FAULT slips or moves,
the Earth QUAKES.
HOW DO FAULTS PRODUCE
QUAKES??

15. 
Where does an earthquake
start?

16. 
FOCUS
--- is the place where the first break happens, where
the fault starts to slip, where first movement takes
place. It is the starting point of the earthquake.
EPICENTER
--- is the spot directly above the focus on the surface
of the Earth.
FOCUS AND EPICENTER

17. 
How would the
surroundings be affected?

18. 
As an earthquake occurs, seismic waves move
out in all directions from the focus.
The energy released during an earthquake is
carried by vibrations called SEISMIC
WAVES.
As the rocks break and move, potential
energy is transformed into kinetic energy in
the form of seismic waves.
SEISMIC WAVES

19. 
TYPES OF SEISMIC WAVES

20. 
1. P waves or primary waves
 fastest waves
 travel through solids,
liquids, or gases
 compressional wave,
material movement is in
the same direction as wave
movement
2. S waves or secondary
waves
 slower than P waves
 travel through solids only
 shear waves - move
material perpendicular to
wave movement
3. L waves or Surface Waves
 Slowly than P and S
waves, but usually
produce larger ground
movements and greater
damage.

21. 
SEISMOGRAPH – device
that can detect and record
seismic waves.
The record of an
earthquake on a
seismograph is called
seismogram.
MEASURING EARTHQUAKES

22.  RICHTER SCALE
-- rates EQs based on measurement of the times and
amplitudes of seismic waves by certain seismograph.
 MOMENT MAGNITUDE SCALE
-- gives measure of the amount of energy released by an
earthquake.
 MODIFIED MERCALLI SCALE
-- rates the effects of earthquakes, which ranges from 1-
12, is based on observations of the intensity of ground
shaking and damage in the areas affected by an
earthquake.
MEASURING EARTHQUAKES

23. 
How Strong is the
Earthquake?
An earthquake may be described in two ways:
1. Intensity - effects on people or
surroundings
2. Magnitude - energy released
*The intensity of an earthquake
gives us an idea of how strong or
weak the shaking is.

24. 
Philippine Institute of Volcanology
and Seismology
PHILVOLCS

25. 
Roman Numerals
( I – X)
Hindu –Arabic
Numerals
1- 9

26. 
PHIVOLCS Earthquake
Intensity Scale (PEIS)

27. 
PHIVOLCS Earthquake
Intensity Scale (PEIS)

28. 
When an earthquake occurs, where would shaking
be greater? Near the epicenter or away from the
epicenter?
 Where would damage be more? Near the
epicenter or away from the epicenter?
Based on your answers to Questions A and B,
where would the intensity be higher? Near the
epicenter or away from the epicenter?
 Suppose an earthquake occurred in Luzon. Would
the intensity be the same all over the Philippines?
EXPLAIN IT!

29. 
DO YOU
LIVE NEAR
AN ACTIVE
FAULT?

30. 
It is one that has moved in the past
and is expected to move again.
It has generated earthquakes before
and is capable of causing more in the
future.
ACTIVE FAULT

31. 
Is there an active fault passing by
your town, province, or region? If
so, are you and your family
prepared for the occurrence of an
earthquake?

32. Prepare homes or schoolrooms by:
 strapping heavy furniture to the walls.
 Check the stability of hanging objects.
 Breakable items, harmful chemicals and flammable
materials should be stored properly.
 Know exit routes.
 Know where fire extinguishers and first aid kits are
located.
 Prepare an emergency supply kit that includes water,
canned food, can opener, clothing, blanket, battery-
operated radio, flashlight, and extra batteries.
 Participate in regular earthquake drills.
BEFORE THE EARTHQUAKE

33.  Stay calm.
 If you are at home or inside a building, stay there.
 Duck under a sturdy desk or table and hold on to it.
 Stay away from glass windows, cabinets, and heavy
objects.
 Beware of falling objects.
 If you are outside, move to an open area.
 Stay away from trees, power lines, and concrete structures.
 Move away from steep slopes which could be affected by
landslides.
 If you are near the shore, move quickly to higher grounds.
Tsunamis may follow.
DURING THE EARTHQUAKE

34. Do not use elevators or enter damaged buildings.
Check yourself and others for injuries.
Check for spills of chemical, toxic, and flammable
materials.
If you need to evacuate, leave a message and bring
your emergency kit.
Listen to the radio for updates.
AFTER THE EARTHQUAKE

36. 
Faults are found not only on land but also
under the sea. When a fault at the bottom of
the sea suddenly moves, the water above it
can be affected.
A sudden push from an underwater fault
can produce a wave called a TSUNAMI.
TSUNAMI

37. 
It is so much more powerful.
It involves the whole depth of the sea, from the
seafloor to the surface.
It travels at the speed of a jet plane. When the
tsunami reaches the shore, it slows down but it
grows in height.
It is very destructive because the force of the
whole ocean is behind it. This is the reason why
whole towns and cities are totally devastated
after a tsunami attack.
TSUNAMI

38. 
When a fault suddenly moves on land, you get
an earthquake. But if a fault suddenly moves in
or near a body of water, you may get a tsunami
in addition to the earthquake.
*Not every fault movement beneath the sea will
produce a tsunami. Those faults that move in a
horizontal direction or sideways will not result in
a tsunami. The fault has to move in the vertical
sense.
HOW ARE EARTHQUAKES
RELATED TO TSUNAMIS?

39. GROUP 1 – Explain and demonstrate the three types of fault
and how do faults produce quakes?
GROUP 2 – Explain and demonstrate where does an
earthquake start and how would the surroundings be
affected?
Group 3 – Explain and show how strong is the earthquake
based on
ACTIVITY

40. 
Earthquakes are always
linked with death and
destruction. Is there anything
good at all about earthquakes?

41. Scientists have used earthquake waves to
figure out the internal structure of the
Earth.

42. 
EARTH’S INTERIOR

43. 
EARTH’S INTERIOR