The document explains the causes and characteristics of earthquakes, including concepts like faults, focus, and epicenter. It details different types of faults (normal, reverse, strike-slip) and stresses (compression, tension, shear) that impact the earth's crust. Additionally, it provides safety measures for earthquake preparedness and the difference between earthquake intensity and magnitude.

1. Earthquake: Faults,
Magnitude,
Intensity, Epicenter
and Focus

2. STAND UP EVERYONE AND LET’S DO THIS!
• TRUE (Dance) • FALSE (Squat)

3. 1. PHIVOLCS stand for
Philippine Volcanoes and
Seas.
FALSE - (Philippine Institute of
Volcanology and Seismology)

4. 2. Earthquake has an epicenter.
True

5. 3. Focus and epicenter is
different to each other.
True

6. 4. Earthquakes are common
in the Philippines
TRUE

7. 5. Earthquakes caused by the
human activities
True

8. You’re a great dancer!

9. What am I?
FO

10. What am I?

11. What am I?
CENTER

12. WHAT IS AN EARTHQUAKE?

13. An earthquake is caused by a sudden
slip on a fault. The tectonic plates are
always slowly moving, but they get stuck
at their edges due to friction. When the
stress on the edge overcomes the
friction, there is an earthquake.

14. What is Fault?
It is a fracture or zone of
fractures between two
blocks of rocks. Faults
allow the blocks to move
relative to each other.

15. NORMAL FAULT
This type of faulting
occurs in response to
extension. Occurs when
the “hanging wall”
moves down relative to
the “foot wall”.

16. REVERSE FAULT
This type of faulting is
common in areas of
compression. Occurs
where the “hanging wall”
moves up or in thrust
over the “foot wall”.

17. STRIKE-SLIP FAULT
A fault on which the
two blocks slide past
one another.

18. Two Types of Strike-Slip Fault
• Left Lateral Strike-Slip Fault • Right Lateral Strike-Slip Fault

19. What are the types
of Stresses in the
Earth’s crust?
1.Compression Stress
2.Tension Stress
3.Shear Stress

20. 1. Compression Stress
Click icon to add picture
It is a type of stress that causes the rocks to push or
squeeze against one another. The force of
compression can push rocks together or cause the
edges of each plate colliding to rise.
Mountains are the results of high-impact
compression stress caused when two plates collided.

21. 2. Tension Stress
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It is the opposite of compression, tension forces
the rock to pull apart. Two separate plates can
move farther away from each other, or the ends
of one plate can move in different directions.
Pangaea is the example of tension stress.

22. 3. Shear Stress
Click icon to add picture
Shear stress usually happens when two
plates rub against each other as they move
in opposite directions. The friction of a
shear stress at the edges of the plate can
cause earthquake.

23. Have you ever experienced a
strong earthquake?
What did you do?

24. Where does an earthquake start?

25. This spot where the
first break occurs is
called FOCUS or
HYPOCENTER

26. Focus
Is the origin or
center of the
earthquake, located
underground.
“Hypo” means
under or beneath.

27. Epicenter
A point on the surface of
the earthquake which is
directly above the focus,
where the earthquake
vibrations reach first.
“Epi” means surface.

28. What is the difference of Focus and
Epicenter?
The focus is the place inside
Earth's crust where an
earthquake originates. The
point on the Earth's surface
directly above the focus is
the epicenter.

29. We cannot prevent natural
earthquakes from occurring but we
can significantly mitigate their
effects by identifying hazards,
building safer structures, and
providing education on
earthquake safety. By preparing
for natural earthquakes we can also
reduce the risk from human induced
earthquakes.

30. Drop. Cover. Hold on.
DROP down onto your hands and knees before the earthquake knocks you down.
COVER your head and neck (and your entire body if possible) underneath a sturdy table or
desk.
HOLD ON to your shelter (or to your head and neck) until the shaking stops.

31. How strong is the Earthquake?

32. Earthquake can described in two ways:
INTENSITY MAGNITUDE

33. INTENSITY
Intensity of an earthquake gives us an idea of how
strong or weak the shaking is or simply by
describing the effects of earthquake on people or
surroundings.
PHILVOLCS uses the PEIS to describe the
intensity of earthquake in the Philippines.

34. MAGNITUDE
Describing the strength of an
earthquake is by magnitude. The
Richter scale – also called the
Richter magnitude scale is a
measure of the enrgy released.
The great the magnitude, the
stronger the earthquake.