This power point is a collection of slides which explain about earthquake with it's causes, impacts and managing strategies

1. Hazardous
Environment
For A- level
Mr. YONAS GEMEDA
November2019
Addis Ababa

2. Learning outcomes
• At the end of this lesson, you should be able
to:
• Describe the reasons and places of
earthquake hazards.
• Briefly explain the causes and impacts
of earth quakes.
• Identify the management strategies of
the earthquake hazards.

3. Introduction to
Hazard

4. Terms Related to Hazard
• What does hazard mean?
• Hazard is a threat that could injure
people and damage the built
environment.

5. Terms related to hazards
• Disaster
• Is a hazard that causes so much damage and
injury that recovery without help is
impossible.
• Risk
• Is the exposure of people to a hazard event.

6. Terms related to hazards
• Vulnerability
The degree to which conditions make a
population more likely to experience a
hazard event
• Resilience
How well a population recovers from a
disaster.

7. Types of Hazard
Based on cause
1. Geologic or tectonic
Earthquakes
Volcanic eruption
2. Geomorphological
mass movement
3. Atmospheric or meteorological
Tropical cyclone, Tornado..

8. Hazards Resulting
From Tectonic
Processes

9. Earthquakes

10. What is earthquake?
• An earthquake is a trembling or
shaking of the ground caused by the
sudden release of energy stored in the
rocks beneath the earth surface.

11. Causes of earth quake
Earth
quake
Anthropoge
nic
Natural/tectonic

12. Causes of earthquakes
• By what?
• Most earthquakes are tectonic( geologic or by
internal force). Some earthquake may be caused
by human activity putting too much stress on
faults.
• Where?
• They occur on :
1. All types of plate boundaries
2. At hotspot
3. Fault lines

13. How ?
• When two plates try to move but become
stuck against each other, stress builds up.
Eventually, the plates break free along a
fault, causing a sudden release of pressure
and releasing a tremendous amount of
energy, which send seismic waves(shock
waves) out from the point of movements…
the focus or the origin of the earthquake.

14. Plate Boundaries as Seismic Zones
• There are four types of seismic
zone :
I. Destructive (convergent)
II.Collision
III.Conservative(trans fault)
IV.Constructive (divergent)

15. Plate Boundaries

16. Distribution of earthquakes

17. Features of earthquakes

19. Impacts of earthquake as a hazard
• Shaking
• Earthquakes send out seismic energy waves, which are
recorded by seismographs.
• The two types of seismic waves are
1. Body waves .. Travel through the interior part
..focus to all direction
• Primary waves (p- waves )
Travel fastest and arrive at a place first.
• Secondary wave (s-waves )
Slowest waves

20. Impacts of earthquake as a hazard
2. Surface waves… travel on the earth
surface away from epicenter..
Travel along the earth waves

21. Hazards and impacts of earthquakes
• Ground shaking
• Surface faulting
Primary
hazards
• Soil liquefaction
• Landslides and rock fall
• Debris flow and
mudflow
• Tsunami
Secondary
hazards

22. Hazards and impacts of earthquakes
Floods from collapsed dams
Release of hazardous materials Fires and spread of diseases
Interruption water supply
Breaking of sewage disposal Loss of public utility
Loss of life
Loss of livelihood Destruction of building

23. Factors affecting earthquake
damages
• The extent of earthquake damage is
influenced by:
Populat
ion
density
Type of rock
and sediment
Strength
and depth
of
earthquake
The
time of
day
Type of
building
Distance
from
center of
earthqua
ke
Economi
c
develop
ment
Secondar
y
hazards

24. Earthquakes and human activities
• Human activities can trigger earthquakes,
or alter the magnitude and frequency of
earthquakes, in three main ways:
Through underground disposal of liquid wastes
By underground nuclear testing and explosions
By mining and fracking

25. Measuring Earthquakes
• The instrument used to measure
seismic waves is a seismometer.
• A seismometer by itself cannot record
the motion that it measures .

26. Measuring Earthquakes
• A seismograph is a recording device
that produces a permanent record of
earth motion detected by a
seismometer usually in the form of a
wiggly line drawn on a moving strip of
paper.

27. Managing earthquakes
• The main ways of dealing with
earthquakes involve better forecasting
techniques, warning system and
emergency procedures, and
improvements to building design and
location.

28. Managing earthquakes
• The paper record of earth vibration is called a
seismogram.
• The seismogram can be used to measure the
strength of the earthquake.
• The total amount of the energy released
(magnitude ) of an earthquake was measured
by Richter scale.
• The 12- point Mercalli scale measures the
intensity (amount of physical damage) of an
earthquake.

29. Thank you
!!! !!!
☺☼☺☹