This document discusses earthquakes and tectonic plate movement. It states that the Earth's crust is made up of plates that move and interact, causing earthquakes and volcanic activity. Earthquakes occur when stresses along faults in the crust are suddenly released. Seismic waves travel outward from the hypocenter or focus point to the epicenter on the surface. Triangulation of arrival times at seismic stations can be used to locate the epicenter. Faults are considered active if they have recently experienced earthquakes and are likely to produce future quakes, such as through the buildup and release of stress along the fault during plate interactions.

3. states that the entire
lithosphere of the Earth
broken into numerous
segments called plates.

4. Distribution of
Active Volcanoes
Earthquake Epicenters
Major Mountain Belts

6. What is an
earthquake?
How does it
occur?

8. EARTHQUAKE

9. The Ring of Fire is
one of the most
geologically active
areas on Earth and
a site for frequent
earthquakes and
powerful volcanic
eruptions.

10. WHAT IS AN EARTHQUAKE?
•An EARTHQUAKE is the sudden
movement of the Earth’s crust.
• it can be a slight or violent shaking
of the ground due to a volcanic
activity or the movement of tectonic
plates, which are the pieces of the
Earth’s crust.

11. the Earth’s crust is covered
with a thick layer of solid rocks.
These rocks were once molten
deep within the earth due to
high pressure and intense
temperature. A crack may occur
across these solid rocks
causing a FAULT.

12. HYPOCENTER OR FOCUS – the point of origin of the earthquake which can be
found within the Earth’s crust.
(it can originate in the continental crust or oceanic crust.)
EPICENTER – the point on the Earth’s surface directly above the hypocenter.

13. CONTINENTAL CRUST – is
the layer of granitic,
sedimentary, and
metamorphic rocks, which
form the continents and
the area of the shallow
seabed close to shore.
OCEANIC CRUST – is a
layer of basalt and gabbro
rocks that underlie the
oceans.

14. SEISMOGRAPH
A seismograph is an instrument
that can record seismic waves.
- Geologists use
seismograph(seismogram) to
determine how strong an
earthquake was. A less powerful
earthquake is shown by short
wiggly lines, while a powerful
earthquake is shown by long
wiggly lines.

15. SEISMIC WAVES – are energy that travel either
through the Earth’s interior or along or near the
Earth’s surface.
Body Waves – travel through
the Earth’s interior.
a. Primary Waves(P-waves) –
travel the fastest.
b. Secondary Waves(S-waves)
– transverse in nature.
Surface Waves – travel across the Earth’s
surface.
a. Rayleigh waves
- Longitudinal waves (L-waves) – waves
having the same direction of vibration as
their direction of travel or wave
propagation.
- Transverse waves – occur perpendicular to
the direction of travel or wave propagation.
b. Love waves (L-waves) – includes transverse
motion.

17. What makes
a FAULT
ACTIVE?

18. Directions: Use triangulation method to locate the
earthquake’s epicenter by making three circles from
the point of the seismic station. The place where the
three circles intersect or nearly intersect is the
earthquake’s epicenter and label it. Use and gather
the materials below for your activity. Carefully follow
the procedure. Answer guide questions and write
your answers on the line provided. You may use
another sheet of paper for your computations and
conversion.
“FIND THE CENTER”

19. MATERIALS:
• Hypothetical records of earthquake waves
• Philippine Map (Use the scaling of the
map)
• Drawing compass
• ruler
• Pencil
• Laboratory notebook

20. PROCEDURE:
Study the data showing the difference in the arrival time of P wave and S-
wave on the three seismic recording stations and complete the table
below.
Recording
Stations
Time difference in
the arrival time of P-
wave and S- wave
(Seconds)
Distance of Epicenter
from the station
(km)
Computed distance on
the map (cm)
(1.5 cm: 200km)
Ex. Calbayog
City
36 Answer: 450km 3.4 cm
Batangas 44.8
Puerto Princesa 32
Davao 38.4

21. Compute the distance of the epicenter from
each of the stations using this formula:
Note: 8 seconds is the interval between the time of arrival of the P-
wave and S-wave at a distance of 100km.
where:
d= distance (km)
Td= time difference in the arrival time of
P-wave and S-Wave (Seconds)

22. WHAT MAKES FAULT ACTIVE?
• A fault is considered ACTIVE if it has moved
repeatedly in the past and is likely to move again.
Earthquakes usually occur in active faults.
• During the movement of faults, energy is stored. This
energy will eventually be released once the fault
overcomes the friction of the movement.
• The energy will radiate outward from the fault toward
all directions in the form of seismic waves until it
reaches the Earth’s surface, which shakes the
ground.

23. The repeated occurrence of earthquakes caused by fault movements can form
mountain. An example is the formation of the mountain ranges in New Zealand.

24. Collision of plates causes some plates to subduct.Subduction is the process by which
the oceanic crust collides with and descends beneath the continental crust.
Subduction zones are known for their high rates of mountain building, volcanic activity
and earthquakes.