powerpoint presentation

1. EARTHQUAKES AND
PLATE TECTONICS
MS. G. MARTIN

2. EARTHQUAKE
 Is the shaking or trembling of the earth caused by pieces of the crust
of the Earth that suddenly shifted.
 The tremendous pressure beneath the earth causes the plates to
move. This movement in the plates compresses or stretches the rocks
along the plate boundaries. When rocks are stretched or squeezed,
they store energy. When these rocks break, the energy is released in
the form of vibrations. These vibrations are earthquakes.

3. Parts of an Earthquake
Focus or hypocenter – is the place within
the Earth where the rock first breaks and
sends out earthquake or seismic waves.
Seismic Waves - are shock waves created at
the hypocenter of the earthquake and send
out in all directions through the Earth.
Epicenter – is the point on the ground’s
surface directly above the focus. The most
violent shaking or vibration occurs here.

4. MAIN TYPES OF FAULTS
 Earthquakes are caused by active faults. In short, an earthquake is
caused by the sudden movement of the two sides of a fault with
respect to another. There are three main types of faults. These are
normal faults, reverse fault, and strike-slip fault. These three
faults differ in the direction of movements of blocks of rocks along
them.
 A fault is a fracture along which the blocks of crust on either side
have moved relative to one another parallel to the fracture.

5. 1. Normal fault
In normal fault, the block
above the fault moves down
relative to the block below the
fault.
This motion is caused by tensional
force.

6. 2. Reverse fault
In a reverse fault, the block
above the fault moves up relative
the block below the fault.
Compressional forces cause this
fault motion.

7. 3.Strike-slip fault
In the strike-slip fault, the
movement of blocks along a fault
is horizontal.
If the block on the far side of the
fault moves to the left, it is called
left lateral, and if the direction of
the movement is rightward, it is
called right lateral.

8. According to the United States Geological Survey, Encyclopedia
Britannica, the deadliest earthquake happened on January 23, 1556.
An 8.0 magnitude earthquake in Shaanxi province (formerly Shensi),
China killed an estimated 830,000 people with damages extending as
far as away as about 270 miles northeast of the epicenter. Ground
fissures, uplift, subsidence, liquefaction, and landslides were some of
the reported geological effects of this earthquake.
Earthquakes also cause formation of fissures. When an earthquake
strikes, it creates fissures into the depth of the Earth in random
location.

9. Fissures
Fissures are long and narrow openings or lines of breakage made by
cracking or splitting, especially in rock or earth.

10. WHAT IS “THE BIG ONE”?
 Seismologist depend on the prerecorded signs such as the deformities on land
structures and seismic activities.
 According to the Philippine Institute of Volcanology and Seismology or
PHILIVOLCS, Metro Manila’s West Valley Fault is already ripe and due for the
next “Big One” within our lifetime.
The “Big One” is an earthquake expected to occur with a magnitude of 7.2
or stronger that would possibly hit the Metro when the West Valley Fault along the
eastern side of Metro Manila cracks. When the “Big One” strikes, this quake can
shake all the cities and even the neighboring cities and provinces situated along
and near fault system.

11. The West Valley Fault runs from the heights of Sierra Madre
down to Laguna. It crosses the eastern side of Quezon City, western
side of Marikina, western part of Pasig, eastern part of Makati, parts
of Taguig and Muntinlupa.
The West Valley Fault has already moved four times in the past
1,400 years. And on the average, the fault moves every 400 years.
The last time an earthquake occurred along the West Valley Fault was
in 1658, and that was 362 years ago.
What is the best thing to do to counter the devastating effects of
earthquakes? Be always prepared.

12. THANK YOU!