1.
EARTHQUAKES
JORIEL J. CRUZ
“Earthquakes have long been feared as
one of nature’s most damaging hazards.
Earthquakes continue to remind us that
nature still can strike without warning
and, after only a few seconds, leave
casualties and damage in their wake.”
GSE 415 EARTH/ENVIRONMENTAL SCIENCE

2.
HOW AN
EARTHQUAKE
HAPPEN?
3 BASIC TYPES OF
FAULTS
EQUIPMENT USE TO
RECORD/MEASURE
EARTHQUAKES
TOPICS
TYPES OF QUAKE
WAVES
SCALE USED TO
MEASURE QUAKES
EARTHQUAKE
PREPAREDNESS
GSE 415 EARTH/ENVIRONMENTAL SCIENCE

3.
WHAT IS AN
EARTHQUAKE?
•Earthquakes are vibrations
produced when rocks break along
a fault. The term earthquake
describes the sudden slip on a
fault and includes the ground
shaking and radiating seismic
waves that is caused by the slip.
Volcanic Activity, or other geologic
processes, may cause stress
changes in the earth that can also
result in an earthquake.
An earthquake is an intense shaking of
Earth’s surface. The shaking is caused by
movements in Earth’s outermost layer.-
https://spaceplace.nasa.gov/earthquakes/en/
GSE 415 EARTH/ENVIRONMENTAL SCIENCE

4.
HOW AN EARTHQUAKE
HAPPENS?
GSE 415 EARTH/ENVIRONMENTAL SCIENCE

5.
Parts of Earthquakes
GSE 415 EARTH/ENVIRONMENTAL SCIENCE

6.
FOCUS
The point below the
surface where the rock
breaks and energy is
released. (This is where
the earthquake
occurred.)
GSE 415 EARTH/ENVIRONMENTAL SCIENCE

7.
LIFESTYLE
BY SAWYER
FAULT
As soon as the rock
breaks, there is
movement along the
broken surface causing
a split in the surface.
GSE 415 EARTH/ENVIRONMENTAL SCIENCE

8.
Faults a break or fracture in the crust of Earth.
The earth’s crust is
constantly experiencing
pressure from forces
within and around it. This
pressure builds up over
time, and eventually
causes the crust to break.
This becomes a fault.
GSE 415 EARTH/ENVIRONMENTAL SCIENCE

9.
Classification of faults according to their relative motion and its parts:
Normal Fault: hanging wall has dropped relative to the
footwall.
Reverse Fault: footwall has dropped relative to the
hanging wall
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GSE 415 EARTH/ENVIRONMENTAL SCIENCE

10.
TYPE OF STRESS
Compression: occurs when crustal rocks are squeezed
together
Can reduce the volume of rocks, can push the rocks
higher up or deeper down into the crust
Tension: the force that pulls rocks apart
Rocks that are pulled apart by tension
tend to become thinner
Shearing: pushes rocks in opposite
horizontal directions
These rocks bend, twist, or break apart as
they slide past each other.
GSE 415 EARTH/ENVIRONMENTAL SCIENCE

11.
3 BASIC
TYPES OF
FAULTS
P
Strike-Slip
Reverse
Normal
Normal fault - when two plates are
moving apart and one side of the fracture
moves below the other; (caused by
tension forces!)
Reverse fault - when two plates collide
and one side of the fracture moves on
top of another; (caused by
compression forces!!)
Strike-slip - when two plates slide past each
other. (caused by shear forces!)

12.
EPICENTER
The seismic waves from
an earthquake are
usually strongest at the
epicenter.This is the
point on the surface
right above the focus.
GSE 415 EARTH/ENVIRONMENTAL SCIENCE

13.
QUAKE OR SEISMIC
WAVES
Quake or Seismic
waves carry energy
from an earthquake
away from the focus,
through Earth’s
interior, and across the
surface Seismic waves are waves that travel through or over Earth. They
are usually generated by movements of the Earth's tectonic
plates (earthquakes) but may also be caused by explosions,
volcanoes and landslides. They can tell us much about the
Earth's structure.
GSE 415 EARTH/ENVIRONMENTAL SCIENCE

14.
MAIN TYPES OF QUAKE/SEISMIC WAVES
There are three basic types of
seismic waves – P-waves, S-
waves and surface waves. P-
waves and S-waves are
sometimes collectively called
body waves.
SURFACE WAVES
BODY WAVES
GSE 415 EARTH/ENVIRONMENTAL SCIENCE

15.
Move out from the earthquakes
focus, the point where energy is
released
Travel the fastest of the 3 waves
Move through solid and liquid layers
of the Earth.
Push and pull rock creating a back-
and-forth (side to side) motion in the
direction the wave is moving
(longitudinal wave)
1.
2.
3.
4.
P Waves also known as primary waves or pressure waves, travel at the
greatest velocity through the Earth.
GSE 415 EARTH/ENVIRONMENTAL SCIENCE

16.
S waves move rocks up and down,
like a wave passing through a rope
when you flick it.
S waves travel more slowly than P
waves but do more damage.
S waves can only go through solid
rock.
1.
2.
3.
S Waves also known as secondary waves, shear waves or shaking waves,
are transverse waves.
S-waves cannot travel through air or water but
are more destructive than P-waves because of
their larger amplitudes

17.
Surface waves are combined P and S waves
that travel along Earth’s surface.
Surface waves are the slowest seismic waves.
They also do the most damage because they
make the ground roll like the ocean.
They are typically generated when the
source of the earthquake is close to the
Earth’s surface.
1.
2.
3.
4.
Surface Waves Surface waves are similar in nature to water waves and travel just
under the Earth’s surface.
Rayleigh waves, also called ground roll,
travel as ripples similar to those on the
surface of water.
Love waves cause horizontal shearing of the
ground. They usually travel slightly faster than
Rayleigh waves

18.
EQUIPMENT USE TO RECORD/MEASURE EARTHQUAKES
To record and measure the vibrations of seismic waves, geologists use instruments called
seismographs. 
Seismograph—A device that records ground movement caused by seismic waves as they move
through Earth.

19.
GSE 415 EARTH/ENVIRONMENTAL SCIENCE

20.
DIFFERENCE BETWEEN MAGNITUDE AND INTENSITY
GSE 415 EARTH/ENVIRONMENTAL SCIENCE

21.
The Mercalli Intensity Scale was developed
by the Italian volcanologist Fr. Giuseppe
Mercalli in 1884 and expanded to include 12
degrees of intensity in 1902 by Adolfo
Cancani. It was modified again by Harry O.
Wood and Frank Neumann in 1931. It is
known today as the Modified Mercalli
Intensity Scale.
Mercalli Scale
The Mercalli Intensity Scale measures the intensity of
an earthquake by observing its effect on people, the
environment and the earth’s surface.
Fr. Giuseppe Mercalli
GSE 415 EARTH/ENVIRONMENTAL SCIENCE

22.
Mercalli Scale

23.
RICHTER SCALE
The Richter magnitude scale (often shortened
to Richter scale) is the most common
standard of measurement for earthquakes.
Charles Richter (1891-1989)
Rating of the size of seismic
waves as measured by a
seismograph.
Accurate measurements for
small nearby earthquakes
not large distant ones.
The Richter scale was developed in 1935 by American seismologist Charles
Richter (1891-1989) as a way of quantifying the magnitude, or strength, of
earthquakes.

24.
Comparison betwen Mercalli and Richter Scale

25.
WHAT TO DO
BEFORE,
DURIN AND
AFTER AN
EARTHQUAKE?
Reference: PHIVOLCS
GSE 415 EARTH/ENVIRONMENTAL SCIENCE

26.
BEFORE
EARTHQUAKE WHAT TO DO BEFORE AN EARTHQUAKE?
KNOW THE HAZARDS:
Familiarize yourself
with earthquake
hazards in your area.
KNOW THE EVACUATION AREA:
Check the nearest route going to
identified area.
PREPARE
EMERGENCY
SUPPLY KIT:
Make it accesible
at all times
PREPARE YOUR HOUSE OR
WORKPLACE
Learn to USE the first aid kit , fire
extinguishers, alarms, switching off
waterlines, gas tanks, and circuit
breakers.
PARTICIPATE DURING
EARTHQUAKE DRILLS. Regularly
practice evacuation procedure.

27.
DURING
EARTHQUAKE WHAT TO DO DURING AN EARTHQUAKE?
DURING SHAKING:
DROP, COVER and
HOLD
STAY CALM and ALERT: Watch for
the falling objects, glass windows,
shelves, cabinets and other heavy
objects that may cause injury.
IF OUTSIDE, MOVE to
an open area.
IF NEAR SHORE, Move
quickly to a higher grounds.
Move away from steep
slopes.
STOP if inside a
MOVING VEHICLE. Do
not cross bridges,
overpass or fly over.

28.
AFTER
EARTHQUAKE WHAT TO DO AFTER AN EARTHQUAKE?
EVACUATE. As soon as
the shaking stops, take
the fastest and safest
way out.
EXPECT AFTERSHOCKS
Put out small fires using
extinguisher.
BE UPDATED: Monitor the
situation from the radio, tv
and others.
CHECK YOURSELF
AND OTHERS FOR
INJURIES