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1. Earthquake
and
Faults
Day 2

2. OBJECTIVES
K : differentiate between focus and epicenter, intensity
and magnitude, active and inactive faults;

3. OBJECTIVES
S : explain why earthquake occurs; and

4. OBJECTIVES
A : appreciate the importance of concepts and ideas
about earthquake.

5. The Philippine, a seismically active region, experience
about five earthquakes a day. Many of these are so
weak that they pass unnoticed. However, some are so
strong that they cause much destruction to buildings,
infrastructures, properties and loss of life.
Renewable Resources & Non-Renewable Resurces

6. Most earthquake are caused by the faulting of rocks. As
two plates move relative to each other, this cause rocks
to slide over one another and change their positions.
Violent tremors of the earth’s surface caused by the
sudden movement of rocks shake large land masses.
Renewable Resources & Non-Renewable Resurces

7. FOCUS
Renewable Resources & Non-Renewable Resurces
The point along a fault where movement first occurs.
EPICENTER
The point on the earth’s surface
immediately above the focus

8. An earthquake may be described
in two (2) ways:

9. Intensity
is determined by observing effects of the earthquake
in different places. Houses, buildings, and other structures
are inspected. People are interviewed about what they
saw (the cabinet fell over), how they felt (I was frightened),
or what they did (I ran out of the house). It gives us an idea
of how strong or weak the shaking is. The Philippine
Institute of Volcanology and Seismology (PHIVOLCS) used
the PHIVO LCS Earthquake Intensity Scale (PEIS) to
determine the intensity level.

10. Magnitude
is a measure of the energy released at the focus, the
source of the earthquake. The released energy can be
calculated from seismograph readings and is usually
expressed by the Richter Scale. Each whole value of the
Richter Scale represents an increase in ground motion by
a factor of 10. An earthquake of magnitude 6 has about 30
times more energy than one of magnitude 5. Obviously,
the greater themagnitude, the stronger the earthquake.

11. The Philippine archipelago is
situated in the collision zone of
the Eurasian plate subducting in
the west and the Philippine Sea
Plate. It leads to the development
of the Philippine Fault System
and other smaller shallow crustal
faults. Fault is a break in a rock
along which movement has
occurred.

12. There are two (2) kinds
of fault:?

13. Active Fault
- is one that has moved in the past and is
expected to move again. Has generated earthquakes
before and capable of causing more in the future.
- are structures that we can identify, but
which do not have earthquakes.
Inactive Fault

14. Ways used by
Scientist to find out
if the fault is active:

15. 1. By checking the
historical records of a
place.

16. 2. By studying the
vibrations, past and
present, that come
from faults.

17. 13. By observing the
surroundings. Example, a
fault may slice through
mountains and form cliffs.
This is not to say that
anyone can spot an active
fault. Scientists need a lot
of training to do that.

18. The End!
Do you have any questions?