ppt-earthquakes and faults

1. Lesson 1
Earthquakes and
Faults
Prepared by:
Sir Ernest Mendoza

2. Motivation:
4 PICS
1 WORD

3. Directions :
1. Identify the 4 given pictures that depict
one situation.
2. Guess what the pictures say all about.
3. Jumbled letters are provided.

11. Lesson Objectives:
1. Describe what a fault is using
models or illustrations;
2. Explain how movements along
faults generate earthquakes;
3. Differentiate the epicenter of
an earthquake from its focus;

12. Cross section of the earth

13. What are Faults?
⮚ It is a break in the Earth’s crust along
which significant movement has taken place.

14. Types of Faults
a. Dip-slip Faults
- Involves vertical movement of blocks of rocks.
- When hanging wall moves down relative to the footwall, the fault
is described as a normal fault.
- When the crust is compressed, the hanging wall moves up relative
to the footwall. This described as a reverse fault.

15. B. Strike-slip Faults - involves the horizontal movement of
blocks of rock.
1. Right-lateral strike slip fault- sideways movement to the right
2. Left -lateral strike slip fault- sideways movement to the left

16. Scientists use different ways to find out if a fault is
active.
1. by checking the country’s historical records.
2. by studying the vibrations, past and present that
come from faults.
3. by observing the surroundings.
4. a fault may cut across a stream and the stream
channel is then shifted
5. a fault may slice through mountains and form cliffs.

18. Activity 1
Where does an earthquake start?
Objectives:
After performing this activity, you should be able to:
1. differentiate between focus and epicenter; and
2. demonstrate how movement along faults affect the surroundings.
Materials Needed:
fault model
scissors
Paste
Long folder

19. Procedure:
1. Print /Photocopy the Fault Model (Figure 12; you can also trace it on paper). Then cut
along the outlines of the two drawings.
2. Fold along the lines and paste where indicated. In the end, you should have a model
consisting of two parts that fit together (Figure 13).
3.The upper surface of the model represents the surface of the Earth. The trace of the fault
on the surface of the Earth is called the fault line. Be ready to point out the fault line
when your teacher calls on you.
4. Pull the two pieces apart (Figure 14). The flat surface between the two pieces is called
the fault plane. This is where fault slip or fault movement happens. Point out the fault
plane when your teacher asks you.
5. The place where the fault begins to slip is called the focus. It is where the first movement
occurs. Thus, the focus is the origin of the earthquake. Be ready to explain it to your
teacher.

20. Figure 1 2. Fault Model Figure 13. (Left) The fault model is made of two parts that fit
together.
(Right) The flat surface between the two parts represents the fault
plane.

22. Earthquake - is a vibration of the Earth due to the rapid release of energy
Focus - the place where the earthquake starts along the fault plane.
Epicenter - the spot on the surface of the Earth that is directly above the focus.
Fault Line – the trace of the fault on the surface of the Earth.
Fault Plane – is the flat surface between the two pieces. This is where fault slip or
fault movement happens.
Focal Length – the distance between
the focus and the epicentre.

23. Types of Earthquake
1. Tectonic Earthquakes – occur when rocks in the Earth’s crust break due to
geological forces created by movement of tectonic plates.
2. Volcanic Earthquakes – occur in conjunction with volcanic activity.
3. Explosive Earthquakes – result from the explosion of nuclear and chemical
devices.
4. Collapse Earthquakes – are small earthquakes in underground caverns and
mines.

24. Intensity of an Earthquake
Intensity - refers the effects and damage caused by an earthquake.
Several factors affect the intensity of the quake.
1. Distance from the epicenter of the earthquake
2. Defective building design and substandard materials
3. Kind of ground (rock,sand, etc.) where structure was built
4. Slope of land where house was built

25. Mercalli Intensity Scale
-in 1884, an Italian volcanologist Guiseppe
Mercalli quantified the effects of an earthquake
through a scale known as Mercalli Intensity
scale.
-it was revised Rossi-Forrel scale (1873) used in
measuring the strength of shaking produced by
an earthquake at a certain location.

26. Table 1. PHIVOLCS Earthquake Intensity Scale
(PEIS)
INTENSITY
SCALE
DESCRIPTION
I Scarcely Perceptible- perceptible to people under
favorable circumstances.
II Slightly felt- felt by few individuals at rest indoors.
III Weak - felt by many people indoors especially in
upper floors of buildings.
IV Moderately Strong - felt generally by people indoors
and by some people outdoors.

27. V Strong - generally felt by most people indoors and
outdoors. Many sleeping people are awakened.
VI Very Strong - many people are frightened; many run
outdoors. Some people lose their balance.
VII Destructive - most people are frightened and run
outdoors. People find it difficult to stand in upper floors.
VIII Very destructive- people are panicky. People find it
difficult to stand even outdoors.
IX Devastating - people are forcibly thrown to ground.
Many cry and shake with fear.
X Completely Devastating - practically all man-mades
structures are destroyed

28. Magnitude of an Earthquake
Magnitude - is a measure of the energy released by the earthquake
measured by an instrument called seismograph or a seismometer.
-The seismograph records the shaking of the ground as wavy lines on
paper.
-The stronger the shaking, the larger the
waves.
-The magnitude is calculated from the
height of the largest wave.

29. -magnitude is expressed using the Richter Scale developed by Charles Richter in
1935.
-the Richter Scale uses Hindu-Arabic numerals, with values from 1 to 10. And it is
logarithmic.
-Earthquake with a magnitude of 2 may or may not be felt. Those that are felt by
most people have a magnitude of at least 4. Magnitude 6 quakes can lead to a
lot of damage in highly populated areas.
-Earthquakes with a magnitude of 7 can
cause severe damage. A magnitude 8 or 9 quake
results in widespread destruction, especially near
the epicenter. Luckily, only one or two occur every year.

30. Seismograph
-the instrument used to detect seismic waves is called a
seismometer.
- a seismometer is attached
to a recorder which produces
a record of the seismic waves.
- a seismometer and a recorder
make up the seismograph.

31. Safety Measures Before, During and After an
Earthquake.
A. What To Do Before an Earthquake
1. Know the earthquakes hazards in your area. Strengthen the
structural designs of your house.
2. Help prepare your homes and schools to keep the safe.
a. Ask your parents to strap or bolt heavy furniture to the wall to
prevent it from falling down during an earthquake.
b. Check if hanging objects inside your home , like ceiling fans
and chandeliers, are stable.
c. Store fragile items, harmful chemicals and flammable materials
in a secured place.

32. 3. Familiarize yourself with the exit routes and the location
of fire extinguishers and first aid kits in your area.
4. Prepare a handy emergency kit that contains canned
goods, bottled water, medicines, flashlight, extra batteries
and battery-operated radios.
5. Participate in regular earthquake drills.
6. Help plan the evacuation areas where family members
can go during emergency situations.

33. B. What To Do During an Earthquake
1. Be calm, be alert and don’t panic.
2. If you are inside a structurally sound building:
a. Quickly open the door, if possible.
b. DUCK-COVER-HOLD. Duck under a sturdy table or
desk and hold on to it or protect your head
c. Stay away from glass windows and heavy furniture
or appliances that may fall down.

34. 3. If you are outdoors, move to an open area.
a. Stay away from trees, posts, power lines and structures.
b. Stay away from steep slopes and landslide-prone areas.
c. Move away from the shoreline and move to higher
grounds because tsunami may occur after an earthquake.
4. If you are in a moving vehicle, stop and get out. Don’t
attempt to cross bridges, underpass, tunnels and flyovers.

35. C. What To Do After an Earthquake
1. Prepared for aftershocks. Once the shaking stops, take fastest and
safest way out of the building. Don’t use elevators nor enter
damaged buildings.
2. Check your self and others for injuries.
3. Check for damaged electrical and water lines.
4. Check spills of chemical, toxic or flammable materials.
5. Extinguish fires in the area to prevent it from spreading.
6. If you need to evacuate your residence, leave a message stating
the place where you are going. Also bring your emergency kit.
7. Keep yourself updated through your battery-operated radios.