Disaster Readiness and Risk Reduction 11
THE NATURE OF DISASTERS AND DISASTER RISK
Module No. 1
1st Quarter, 2nd Semester
Time Allotment: 2 Weeks
Learning Competencies:
1. Explain the meaning of disaster
2. Differentiate the risk factors underlying disasters
3. Describe the effects of disasters on one’s life
Learning Objectives:
By the end of this module, the students will be able to:
1. Explain and distinguish the concepts of hazard, disaster, and disaster risk.
2. Explain how and when a hazard becomes a disaster.
3. Describe the effects of disasters on life, property, and the environment.
4. Describe and analyze disasters from different perspectives.
Pre –Assessment/Review
Answer the following questions briefly:
1. What is a disaster and how does it differ from a hazard?
______________________________________________________________________________
______________________________________________________________________________
2. When does a situation can be considered a disaster?
______________________________________________________________________________
______________________________________________________________________________
Introduction of the lesson
“We cannot eliminate disaster (hazard), but we can mitigate the risk. We can reduce
damage and save more lives.” –Ban Ki-Mon, the Secretary-General of the United Nations
Content/Lesson Proper
Lecture-Discussion of Topic
A hazard is a threat or harm that has the potential to cause damage (e.g., injury,
destruction of properties, environmental degradation) to a community.
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There are two main types of hazards: Natural and Man-made. These two differ greatly in
terms of their causes, scope, and effects on life, property, and the environment.
A disaster is any event that causes widespread human, economic, and environmental
losses or impacts that seriously disrupt the normal functioning of a community.
When an event causes a significant number of dead or missing people in an area, it is
considered a disaster.
The level of severity of the disaster is determined based on the number of human lives
missing or lost and on the condition of the survivors. An event is also considered a disaster
according to the assessed cost of repairing or rehabilitating the structures and public
infrastructures that have been damaged or destroyed. An event is also considered a disaster
based on the amount of income lost from work, livelihood, and other economic activities that
have been stopped or slowed down due to the disaster.
Disasters usually follow hazards that are not anticipated. When a disaster occurs, the
community affected may lose its ability to cope with the loss and damage using its own
resources. Hence, disasters may be prevented if proper and effective disaster plans are in
place.
Disaster Risk may be specific to a location or condition of a community. Usually, if
certain hazards are frequent in a specific location or if the present situation of a community
puts it in a dangerous position, the disaster risk becomes a vital consideration in defining the
safety of the people in that community.
There is no way to escape hazards because they are part of our life. Every day and
everywhere, there is a hazard. Hazards can be identified but difficult to avoid. Because hazards
can be recognized, a community that is hazard-prone may increase its disaster risk especially if
it is not equipped or prepared for the possible disasters arising from that hazard.
EFFECTS OF DISASTER
The effects of disasters vary, mostly depending on the severity of the exposure of life,
property, and the environment to the hazard. Usually, the severity of the effects of a disaster is
higher in the community directly affected by the hazard. Although the severity becomes lower
in nearby communities of the affected community, the effects may still be felt and may be
significant.
According to measurable severity, the effects of disasters are primary, secondary, or
tertiary.
Primary effects are direct situations arising from the disaster itself. For example, when a
strong typhoon hits a village, it can cause primary effects such as flooding, destruction of
houses, damage to property, and loss of life.
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Secondary effects are situations resulting from the primary effects. Among the
secondary effects of a strong typhoon that has hit a village is the disruption of electrical and
water services because of damage to power and water lines.
Tertiary effects are those that are not experienced as a disaster is taking place but can
be felt some tie after the disaster has occurred. It may also develop from primary or secondary
effects that have become permanent and may change a natural process in the community.
AFFECTED COMPONENTS
Indeed, the effects of disasters can be complex and widespread, depending on the
damage done to those that are affected, namely, the people, the buildings and infrastructure,
the economy, and the environment.
People
After a disaster takes place, the number of casualties is assessed. In most cases and
depending on the severity of a disaster, the actual number cannot be achieved. There may be
missing persons who may be presumed dead. The number of people injured or who have
gotten sick due to the disaster is also considered. In post-disaster assessments, the estimated
number of persons who have been evacuated or relocated is also calculated.
The loss of family members, friends, and other loved ones is the most tragic effect of
disasters on people. The pain is exacerbated when loved ones remain missing even years after
the disaster.
Buildings and Infrastructure
Homes, buildings, and other infrastructure are important components that are
considered in the aftermath of a disaster. For people who have been affected by a disaster, the
reestablishment of their homes, workplaces, commercial sites, and similar structures is a
priority. Buildings that are considered affected by the disaster are those that have been
damaged structurally or architecturally, have collapsed, or have been leveled to the ground and
even buried, rendering them inhabitable. Any building, field, or ground that has lost its capacity
to serve its designed purpose is tantamount to being useless and is considered a loss.
With the damage to their homes, the people of the affected community do not just lack
shelter from the elements; they have also lost most of their properties, if not all, and have to
practically rebuild their lives as they slowly replace what they have lost.
Economy
Regardless of the severity of a disaster, its effects on the economy of the affected
community are definitely felt. An economy is not a single entity that functions alone. It involves
all sectors of society such as business, transportation, and communication. Hence, when a
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disaster strikes a community, its economy is among the first to be affected because of the loss
of livelihood, employment, and even tourism opportunities for the community.
With the damage to buildings and public infrastructure comes the loss or delay of
essential services such as electrical power, fuel, sewerage, telecommunications, and water. This
hampers the operations of households, businesses, companies, and schools. This damage to
public infrastructure also disrupts the operations of transport services, and this, in turn, affects
the movement of people, goods, and services. All these have serious implications on the
economic life of a community.
Environment
Disasters can cause negative effects on the air, soil, water, and ecosystems in a
community.
Air quality is compromised when harmful particulates are released into the air during
disasters such as volcanic eruptions, explosions, and nuclear plant emissions. These particulates
include ash, dust, heavy metals, and smoke. They do not stay suspended but are deposited into
the environment and can contaminate the ground, bodies of water, and even human, animal,
and plant life.
Aside from absorbing air particulates from man-made disasters, the soil or land suffers
other effects such as erosion from flash floods and landslides, cracks and fissures from
earthquakes, and changes in its quality due to its absorption of chemicals. Erosion is the
process by which soil is carried away by the wind, water, and other agents. As a natural process,
this happens gradually or over a long period of time. However, disasters such as floods and fires
hasten the process.
Disasters affect water in its various aspects: as groundwater, in bodies of water and
water containers such as swimming pools and water tanks. The water can be polluted by dust
and other particulates, and by decaying organic matter brought about by the disasters. The
degradation of water quality can cause fish kills, death to marine life, and disease and other
health problems in people.
An ecosystem is a complex community involving the interaction of animals, plants, and
microorganisms with the nonliving components of that area. The natural balance of ecosystems
is gravely affected by disasters.
PERSPECTIVES ON DISASTERS
Most people would look at disasters from the same perspective. As humans, the first
thing we notice in the aftermath of a disaster is its effects on fellow humans. However, to
evaluate the overall results of a disaster, disaster experts examine them from a different point
of view.
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The physical perspective includes the visible or tangible materials, whether natural or
man-made, which have been affected by a disaster. The altered or removed structures may
change the landscape, zoning, and accessibility of an area.
The psychological perspective refers to the people’s emotional, cognitive, or
interpersonal reaction to difficulties. Catastrophic events can cause shock, terror, anxiety,
disbelief, nightmares, trauma, social withdrawal or alienation, or depression to victims.
Traumatic events or situations can cause long-term depression and can affect the person’s wellbeing. Any neglect of psychological support could impair efforts toward physical rehabilitation.
This is why the DSWD (Department of Social Welfare and Development) becomes vital in postdisaster management. This government agency empowers people and aims to improve their
quality of life in the aftermath of the disaster.
The sociocultural perspective centers on the response of the people, whether victims or
not, to emergency situations and to the kind of assistance they receive. The characteristics of
affected families such as their religions, customs, attitudes, beliefs, and values can influence
their approach to or their recovery from the disaster.
The economic perspective focuses on the disruption of economic activities in the
community. Disaster, whether small- or large-scale, brings about serious economic
consequences. Disaster loss is usually assessed in terms of injuries and death, destruction of
fixed assets and infrastructure, and disruption in the flow of goods and services that can
obviously affect economic factors such as GDP (Gross Domestic Product), growth rates,
indebtedness levels, and fiscal deficits.
The political perspective deals with how government services are used to reduce loss or
damage by preparing for and preventing disasters. This perspective is critical because in some
cases, there exist inequities in societies that create political prejudice in developing plans and
policies related to disaster risk reduction and recovery plans.
The biological perspective takes into consideration the potential for infectious or
communicable diseases after a disaster takes place. In the aftermath of a disaster, humans and
animals that have been injured become susceptible to infections. The entry of the virulent
organism in an unbalanced ecosystem becomes easier in a crowded area, especially in
evacuation and distribution centers, where virus transmission happens through dispersal, direct
contact, and biological agents such as rodents.
Self- Check Test/Practice Exercises
Answer this question briefly:
1. What are the effects of drought in terms of severity?
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
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Evaluation Activities
Identify the following statements below. Write your answer in the space provided.
______________1. It is an event that causes widespread human, economic, and environmental
losses or impacts that seriously disrupt the normal functioning of a community.
______________2. It may be specific to a location or condition of a community.
______________3. He once said, “We cannot eliminate disaster, but we can mitigate the risk.”
______________4. It is a devastating outcome that results from natural hazards.
______________5. After a disaster takes place, the number of casualties is assessed.
Assignments & Summative/Post Assessment
Using a graphic organizer, make a summary of today’s lesson. Make it brief but accurate. Use
the space below for your answer.
References:
Disaster Readiness and Risk Reduction, DIWA SHS Series, Oliva M. D.G., pages 3-18
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Disaster Readiness and Risk Reduction 11
EXPOSURE AND VULNERABILITY
Module No. 2
1st Quarter, 2nd Semester
Time Allotment: 2 Weeks
Learning Competencies:
1. Analyze disaster from the different perspectives (physical, psychological, socio-cultural,
economic, political, and biological).
2. Explain the meaning of vulnerability
3. Explain why certain sectors of society are more vulnerable to disaster than others.
Learning Objectives:
At the end of this module, the students will be able to:
1. Explain the meaning of vulnerability and exposure.
2. Recognize the connection between vulnerability, exposure, and hazards.
3. Enumerate elements exposed to hazards.
Pre –Assessment/Review
Answer the question briefly. Write your answer in the space provided.
1. Vulnerability - ________________________________________________________________
2. Exposure - ___________________________________________________________________
3. Disaster Risk - ________________________________________________________________
4. Disaster - ____________________________________________________________________
5. Hazard - _____________________________________________________________________
Introduction of the lesson
You have learned in the previous module that a hazard may not necessarily lead to a
disaster if a community has adequately prepared for it. The disaster risk may be determined by
two factors: vulnerability and exposure of the community to the hazard. These two
determinants are important in making the community ready for any hazard.
Content/Lesson Proper
Lecture-Discussion of Topic
THE CONCEPT OF VULNERABILITY
The International Federation of Red Cross and Red Crescent Societies or IFRC defines
vulnerability as “the diminished capacity of an individual or group to anticipate, cope with,
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resist, and recover from the impact of a natural or man-made hazard.” Meanwhile, according to
the United Nations Office for Disaster Risk Reduction, vulnerability is “the characteristics and
circumstances of a community, system, or asset that make it susceptible to the damaging
effects of a hazard.”
Vulnerability is situation-specific. If earthquakes are frequent in a particular region, it
does not mean that all provinces in that region are vulnerable.
Vulnerability is also hazard-specific. This means that a community that is vulnerable to
earthquakes does not necessarily mean that it is also vulnerable to typhoons. Hazards have
different characteristics that influence the disasters that are likely to generate.
There are various factors that must be considered to assess the level of vulnerability of
an area or community. These factors can affect one another or can lead to other factors.
Proximity to a hazard event | An area frequented by a certain hazard predisposes it to
high vulnerability. An earthquake, as an example of a hazard, is more likely to happen in the
Philippines than in Brazil because the Philippines is situated along the Pacific Ring of Fire where
frequent seismic activities occur.
Population density near a hazard event | Population differs from population density.
Population refers to the number of individuals inhabiting a particular space at the same time. If
people are distributed evenly in an area, the impact of disaster may be reduced to a minimum.
On the other hand, population density refers to the number of individuals living in an area in
relation to the size of that area. If all individuals crowd in one portion of a place, there is little
space and time to escape from a hazard.
Capacity and efficiency to reduce disaster risk | The capacity of a community to reduce
disaster risk includes the accessibility and availability of services and facilities that help in
preparing for or during disasters. Fortunately, in the Philippines, super typhoons may now be
accurately predicted by the Philippine Atmospheric Geophysical and Astronomical Services
Administration (PAGASA) through the use of modern equipment and technology.
Building codes and disaster policies | Buildings and other structures may increase
disaster risk. When they fall or collapse due to a hazard such as an earthquake, they can cause
injury and even loss of lives. Thus, in the design and construction of buildings, possible hazards
should be considered.
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THE CONCEPT OF EXPOSURE
Geoscience Australia defines exposure as “the elements at risk from a natural or man-made
hazard event.” These elements include the individuals; households or communities;
properties; buildings and structures; agricultural commodities; livelihoods; and public facilities,
infrastructure, and environmental assets present in an area that is subject to potential losses.
Generally, the more a community is exposed to hazard factors, the higher the disaster risk.
The concept of exposure and vulnerability are distinct. A community can be exposed
but is not necessarily vulnerable.
ELEMENTS EXPOSED TO HAZARDS
Generally, there are three main elements that are considered in the exposure of a
community hazard.
1. Physical elements – These are the elements that are tangible or can be visually seen.
Examples are landscapes, inhabitants, buildings, and other structures that make up the
environment. Some are measurable such as population density.
2. Socioeconomic elements – These comprise the institutional and government systems that
dictate the kind of well-being and lifestyles of communities. All these can be altered, enhanced,
or even questioned when exposed to hazards. In general, socioeconomic elements refer to the
manner of social interactions and not the individuals or structures that are involved in the
system.
3. Environmental elements – These include the ecosystems and natural processes that are
exposed to hazard events. Organisms depend on the environment for survival. Human activities
such as overgrazing, deforestation, and exploitation of natural resources strip the environment
of its natural abilities to protect itself from any natural hazard.
THE RELATIONSHIP OF HAZARDS, EXPOSURE, AND VULNERABILITIES
Hazards are possible threats that may come unexpectedly or otherwise. A hazard can
lead to a disaster in a community if (a) the community is exposed to it and (b) the community’s
circumstance or situation makes it vulnerable to the hazard. These two determinants of
disaster risk must be controlled in order to minimize or prevent the disaster.
The combination of exposure and vulnerability determines the level of disaster that
communities will most likely experience. This, along with high exposure and high vulnerability,
can cause extreme disaster even if the hazard is deemed as a small scale.
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HAZARDS
HAZARDS
HAZARDS
VULNERABILITY
DISASTER
DISASTER RISK
EXPOSURE
HAZARDS
HAZARDS
HAZARDS
Given the coastal community’s high exposure to typhoons, let us now assess its level of
vulnerability.
Proximity to disaster: If the community is directly and frequently hit by typhoons, then
its vulnerability to disasters associated with them is high. The fact that the community is
located in a coastal area makes it more vulnerable because it will experience two hazards:
typhoon and storm surge.
Population density: If the community has a large number of populations in exposed
areas, the impact of the hazards will be more severe. In a community with large population size,
most members would not be well sheltered, making them become more vulnerable to the
hazards.
Capacity and efficiency to minimize disaster risk: If the community does not have any
community disaster preparedness plans in place, it becomes more difficult to face the hazard
without expecting any disaster.
Building codes and disaster policies: Houses built in coastal areas are usually made of
light materials. If a typhoon hits the community, a large number of houses may be unroofed.
The location of the houses and other structures in the community must also be considered.
Self- Check Test/Practice Exercises
Answer the question based on your own understanding. Write your answer in the space
provided.
Differentiate hazards, exposure, and vulnerabilities from one another by giving an example
based on the actual situation.
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
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Evaluation Activities
Identify all the possible elements exposed to the volcanic eruption of Mt. Mayon in Albay.
1. Physical elements ______________________________________________________________________________
______________________________________________________________________________
2. Socioeconomic elements ______________________________________________________________________________
______________________________________________________________________________
3. Environmental elements ______________________________________________________________________________
______________________________________________________________________________
Assignments & Summative/Post Assessment
The mayor would like to develop a remote area in your municipality. However, in that area,
flooding usually occurs after prolonged rain. As an urban planner, what structures would you
suggest to be put up in that area? Can schools and houses be constructed there? Indicate
structures on the given layout plan and write notes on the type of construction materials to be
used, land modifications to be done, and other important considerations you would like to have
in minimizing the vulnerability of the area of flooding.
10 MASL
Mountain Range
Area for development
30 MASL
Residential Communities
References
20 MASL
MASL – meters above sea level
Disaster Readiness and Risk Reduction, DIWA SHS Series, Oliva M. D.G., pages 19-30
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Disaster Readiness and Risk Reduction 11
BASIC CONCEPT OF HAZARD
Module No. 3
1st Quarter, 2nd Semester
Time Allotment: 2 Weeks
Learning Competencies:
1. Recognize vulnerabilities of different elements exposed to specific hazards
2. Differentiate among hazards, exposure, and vulnerabilities and explain the relationship of
the three to disaster risk
3. Define and cite examples of the types of hazards
4. Explain the impact of various hazards on people and the environment
Learning Objectives:
At the end of this module, the students will be able to:
1. Define hazards;
2. Give examples of the types of hazards;
3. Determine the manner by which hazards can be profiled; and
4. Explain the impact of various hazards on different exposed elements.
Pre –Assessment/Review
Answer the following questions briefly.
1. What are the two types of hazard? _______________________________________________
2. What is the difference between the two types of hazard? _____________________________
______________________________________________________________________________
______________________________________________________________________________
Introduction of the lesson
The concept of hazard was mentioned in Module 1 in the context of disasters and
disaster risk. Again, hazards may cause disasters. They either increase or decrease the risk of
disasters in a certain community. Hazards are events that pose threat, danger, or risk to any
element exposed to them. Hazards are possibilities. They can strike anywhere and anytime. As
explained in Module 2, hazards result in disasters if a community is left both exposed and
vulnerable to that hazard. Hence, it should be remembered that extreme hazard events are not
always associated with disaster. It is actually the circumstance of that community that causes a
hazard to bring in disaster.
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Content/Lesson Proper
Lecture-Discussion of Topic
TYPES OF HAZARDS
Natural hazards are those that are caused by physical and biological elements in the
environment. These are natural events that may not be controlled by humans such as
earthquakes, floods, landslides, tornadoes, tsunamis, typhoons, and wildfires.
Natural hazards are inevitable. They are part of the natural processes of Earth
operating throughout Earth’s history. Hence, it would be best to leave them to operate on their
own rather than intervening or altering their natural course.
Man-made hazards, also called technological hazards, are those caused by factors that
are generally traced to human errors, intent or negligence, or glitches in technology. These
include bomb explosions, chemical spills, nuclear plant blasts, radioactive emissions, and wars.
If you have noticed, these operations are all products of the advancing technology and lifestyle
of humans. The continuous development of technology poses more hazards not just to the
creators themselves, but also to their environment.
PROFILING HAZARDS
Profiling hazards is important in predicting the possible disasters that a certain hazard
can bring. They are useful in planning for a disaster especially if the same impacts are likely to
be brought by a hazard that frequents a certain place.
Hazards can be profiled in different ways: magnitude of event (high0scale or low-scale),
frequency (number of times in a year), duration (short-term or long-term), and casualty of
effects (direct or indirect).
Magnitude or Strength of the Event | The magnitude of the hazard can be assessed by
the measurements obtained from scientific instruments. Sometimes, scaling can vary
depending on the reference tables per country. For example, magnitude 5.0 above is
considered high scale in earthquakes based on PHIVOLCS or Philippine Institute of Volcanology
and Seismology. Floods reaching 1.0 meter is likewise considered high-scale. Typhoons with
winds up to 150kph are deemed strong and powerful.
Frequency | The frequency of the hazard that occurs in an area is important because it
tells its proneness to the hazard. This is usually, but not always, associated with the area’s
geographical location on Earth or its topographical condition.
Duration of Impact | The impact of hazards varies on duration. The assessment of the
duration is either short or long. In earthquakes, for example, the length of shaking, trembling,
and even the after-shocks are recorded.
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Casualty of Events | The impact of hazards can be assessed based on the casualty of
events, that is, whether the exposed elements receive the likely disaster directly or indirectly.
Sometimes, other elements that are not visibly present at the site of the event also suffer some
degree of consequences because all communities interact within and outside their territory.
Because the impacts of hazards vary from place to place and season to season, it is
important to assess the impact of every hazard so that similar events in the future may be
prevented.
HAZARD-PRONE AREAS
A hazard-prone area is a
location where the natural hazard
is likely to happen if preventive
measures are not implemented.
Mainly to its geography, the
Philippines is considered prone to
natural hazards, and hence natural
disasters as well. It is situated along
the Pacific Ring of Fire, an area
surrounding the basin of the Pacific
Ocean where many volcanoes have
formed. Thus, seismic activities
such as earthquakes and volcanic eruptions frequently occur in the region. Around 90 percent
of the world’s earthquakes occur in this region.
Another reason the Philippines is considered a hazard-prone area is its location in the
Western Pacific Basin, the part of the world that is most often visited by typhoons. The region is
also called the typhoon belt. This explains why an average of 20 typhoons hit the country every
year.
IMPACT OF HAZARDS
The impacts of hazards are likely outcomes of disaster. The exposed elements will
initially receive all the negative impacts. In some cases, however, not all impacts of hazards are
adverse. Some natural hazards result in changes that may be beneficial or supportive of the
other existing elements:
1. Physical elements. People, buildings, roads, poles, bridges, and all other material objects
may be ruined by hazards. Volcanic eruptions, explosions, fire, or lightning may instantly burn
or incinerate objects that it comes in contact with. These are possibilities still depend on many
factors that increase or decrease the disaster risk of a community.
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2. Socioeconomic elements. The positive impacts of hazards on the socioeconomic elements
may be in the form of introducing new habits, practices, systems, or values that may be geared
towards the values of resiliency and recovery.
3. Environmental elements. Just like other exposed elements, perhaps the initial impact of
hazard to the ecosystems and other organisms in them may be disastrous. However, in some
cases, due to adaptation or because natural hazards are natural events and hence part of the
natural cycles on Earth the occurrence may benefit certain components of Earth.
Self- Check Test/Practice Exercises
Answer the question briefly. Write your answer in the space provided.
How will you differentiate Natural hazard to Man-made hazard?
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
Evaluation Activities
Answer the question based on your own understanding. Write your answer in the space
provided.
Think of your surroundings. Are you in an area that is prone to hazards? What poses the risks?
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
Assignments & Summative/Post Assessment
Based on what you have learned, make a poster of your understanding. You may use the space
below for your work. You must show your understanding of the lessons that we discussed. You
may also use coloring materials in your work.
References
Disaster Readiness and Risk Reduction, DIWA SHS Series, Oliva M. D.G., pages 31-40
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Disaster Readiness and Risk Reduction 11
EARTHQUAKE HAZARD
Module No. 4
1st Quarter, 2nd Semester
Time Allotment: 2 Weeks
Learning Competencies:
1. Identify various potential earthquake hazards
2. Recognize the natural signs of an impending tsunami; and
3. Analyze the effects of the different earthquake hazards
Learning Objectives:
At the end of this module, the students will be able to:
1. Identify various potential earthquake hazards
2. Determine the effects of different earthquake hazards
3. Recognize and identify the natural signs of an impending earthquake
Pre –Assessment/Review
Identify the following statement below. Write your answer in the space provided.
_______________1. This occurs when ground movement happens on a fault line and breaks
through to the surface.
_______________2. An instrument used to measure movements in Earth’s surface.
_______________3. The shaking of the ground is caused by the passage of seismic waves,
forms of energy that travel through the different layers of Earth caused by vibration or
movement.
_______________4. The word “tsunami” is a Japanese word that means ____________ coined
as such because of the destructive effects experienced by the Japanese living on low-lying
coastal communities.
_______________5. Landslides may happen during or after an earthquake when a weakened
section of landfalls off primarily due to gravity.
Introduction of the lesson
Earthquakes have been occurring as part of Earth’s normal functioning. Earthquakes in
the Philippines happen more frequently because of their geographical location. The Philippines
is one of the countries situated near the Pacific Ring of Fire, an area recognized to have
frequent and active earthquakes and volcanic eruptions.
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Content/Lesson Proper
Lecture-Discussion of Topic
POTENTIAL EARTHQUAKE HAZARDS
Ground shaking – The shaking of the ground is caused by the passage of seismic waves,
forms of energy that travel through the different layers of Earth caused by vibration or
movement. The intensity of ground shaking depends on the geological makeup of the ground,
the duration and intensity of the earthquake, and the proximity of the area to the epicenter
(the area on the surface of Earth where the origin of the earthquake is).
Ground rupture – This occurs when ground movement happens on a fault line and
breaks through the surface. This may happen in an instant during an earthquake. Slowly, the
ground cracks and eventually breaks apart. Most of the time, fault rupture follows preexisting
faults known as zones of weakness. Structures that are built exactly on the fault or along the
span of the fault or along the span of the fault are likely to experience severe damage and thus
have higher disaster risks.
Liquefaction – This occurs when seismic shaking causes loose materials in the soil to mix
with groundwater or soil saturated with water. Eventually, the soil behaves like quicksand that
has lost its strength to hold and support objects on top of it.
Earthquake-induced ground subsidence – Subsidence is the lowering of land due to
various causes, one of which is the earthquake on a fault line. The movement of the ground
during an earthquake could be horizontal, vertical, or both. Depending on the slope, one of the
areas broken up by the movement may be lowered compared to the elevation of the other
pieces of land. This lowering becomes permanent, making the general elevation of the land
uneven.
Tsunami – The word “tsunami” is a Japanese word that means “harbor wave,” coined as
such because of the destructive effects experienced by the Japanese living on low-lying coastal
communities. The term is now generally used to mean a series of waves that are generated by a
sudden displacement on the ocean floor caused by a large-scale undersea landslide or
earthquake, submarine volcanic eruption, or even a large meteor crash at sea.
Earthquake-induced landslide – Landslides may happen during or after an earthquake
when a weakened section of landfalls off primarily due to gravity. The weak land may be due to
its composition of frail rocks or its soft foundation. Sometimes, the land becomes weak due to
man-made activities that induce erosion such as deforestation, excavation, mining, and
quarrying, or the sudden breakup of soil due to thunder and other vibrations from natural
ground activities.
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EARLY WARNING SIGNS OF EARTHQUAKE HAZARDS
At present, there is no instrument that can accurately tell the time and place of an
impending earthquake. What can be detected, however, are the initial seismic waves that serve
as the precursor of an earthquake.
A seismometer is an instrument used to measure movements on Earth’s surface. It can
detect vibrations from seismic waves generated by earthquakes and volcanic eruptions. A
seismic wave is a form of energy that travels through the interior of Earth. The two types of
seismic waves are the p-waves and the s-waves.
The p-waves of seismic action is usually the first one to be recorded. Seconds after the
p-waves are the s-waves which carry most of the energy of the seismic activity. Once these
seismic waves are detected by the seismometer, a seismograph immediately draws the tremor
on paper. A zigzag line means a detected tremor as opposed to a plain straight line where no
movement is felt.
Seismologists observe and collect seismic waves in areas that are prone to earthquakes.
They closely monitor seismic activities or any patterns thereof to give them an idea of possible
releases of energy from the interior of the Earth.
PRECAUTIONARY AND SAFETY MEASURES BEFORE, DURING, AND AFTER AN EARTHQUAKE
Unlike a typhoon or a volcanic eruption, an earthquake is not predictable. It is therefore
very important to be always prepared. The following are some helpful tips that you can do.
BEFORE AN EARTHQUAKE
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Prepare a survival kit. It should contain at least the following items: bottled water,
canned goods and can opener, first-aid kit, battery-powered radio, flashlight with
working batteries, and clothes.
Avoid placing breakables on high shelves or cabinets. These items can easily fall even by
a slight shake.
Check regularly the stability of hanging objects such as ceiling fans and chandeliers.
Make sure that these objects are securely fastened.
Fasten heavy furniture to the walls or floor. Tall cabinets can be secured by hooking
them up against the wall.
Know the emergency numbers of the police. Make sure all family members know these
numbers.
DURING AN EARTHQUAKE
If you are indoors:
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Stay calm. Duck under a sturdy table and protect your head. Remember the DCH (Drop,
Cover, and Hold on) method.
Stay away from glass windows and doors, and heavy furniture.
Watch out for debris or objects.
Never use an elevator to get out of the building. If you are inside the elevator, press the
button for the nearest floor and get off immediately.
If you are outdoors:
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Stay clear of buildings, trees, light posts, power lines, and other structures that could fall
collapse on you.
If you are in a mountainous area, be alert for falling rocks and other debris. If you are in
a coastal area, move to higher ground in case a tsunami follows after the earthquake.
If you are driving or inside a car:
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Slow down and turn on the hazard lights to alert other drivers. Stay inside the car until
the shaking stops.
Avoid pulling up near or under bridges, overpasses, and power lines that may fall or
collapse.
If you are on a bus or a train:
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Hold tightly to the strap or handrail.
Stay inside and listen to the instruction of the train staff. Wait until it is safe to go out of
the vehicle.
AFTER AN EARTHQUAKE:
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Expect aftershocks so remain calm.
Check yourself and others for injuries.
Stay away from downed or damaged power lines.
Check for damaged electrical wiring.
Inspect gas tanks for leaks. Report the authorities immediately if you suspect a gas leak.
Tune in to local radio stations and listen for any news and danger reports.
Stay out of damaged buildings and areas with broken glass and debris.
Follow the emergency plan or the instructions of building personnel if you are inside a
building.
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Self- Check Test/Practice Exercises
Answer the question briefly based on your own perspective.
You were going to explain to a 5-year old child the Drop, Cover and Hold in case of
emergency, how will you explain it? Give some tips and advice on how will you handle it most
especially when there is already a hazard. Write your answer in 5-10 sentences in the space
below.
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
Evaluation Activities
Answer the following question briefly. Write your answer in the space provided.
1. What should we avoid during an earthquake? ______________________________________
______________________________________________________________________________
______________________________________________________________________________
2. What will you do if your 4-year old little sister can’t stop playing even if an earthquake is
ongoing? ______________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
Assignments & Summative/Post Assessment
Summarize the whole quarter using 5-10 sentences. What did you learn and how will you apply
it on real life situation? ___________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
References
Disaster Readiness and Risk Reduction, DIWA SHS Series, Oliva M. D.G., pages 41-50
Prepared by:
Ms. Ma. Abby Gale V. Ignacio
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