Module
5Earthquake Hazards
What I Need to Know (Learning Objcetives) After going through this module, you are expected to:
1. analyze the effects of the different earthquake hazards;
2. recognize the natural signs of an impending tsunami; and
3. interpret different earthquake hazard maps.
What I Know (Pretest)
Direction: Choose the letter of the best answer and write this on your answer sheet.
1) ___________ is the perceptible shaking of the surface of the Earth resulting from sudden release of energy in the Earth’s crust that creates seismic waves. a. Earthquake c. Sinkhole
b. Landslide d. Tsunami
2) It is produced by sudden movement along Earth’s faults and plate boundaries. a. quibolic earthquake c. tsunamic earthquake
b. tectonic earthquake d. volcanic earthquake
3) It is the perceived strength of an earthquake based on relative effect to people and structures; generally higher near the epicenter.
a. intensity c. magnitude
b. level d. strength
4) It is produced by movement of magma beneath.
a. laharic earthquake c. tectonic earthquake
b. seismic earthquake d. volcanic earthquake
5) It is based on instrumentally derived information and correlated strength with the amount of total energy released at the earthquake’s point of origin. a. intensity c. magnitude
b. level d. strength
6) It refers to the disruptive up-down and sideways motion experienced during an earthquake.
a. ground rupture c. liquefaction
b. ground shaking d. tsunami
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7) A __________ is a fracture on which one body of rocks slide past another. a. bedrock c. magma
b. fault d. sinkhole
8) __________ takes place when loosely packed, water-logged sediments at or near ground surface lose their strength in response to strong ground shaking. a. Ground rupture c. Liquefaction
b. Landslide d. Tsunami
9) It is the production a series of giant waves greater than 5 meters as a result of under-the-sea geological processes.
a. surfing waves c. tsunami
b. tidal wave d. wave
10) Which of the following is NOT an earthquake hazard?
a. earthquake-induced landslide c. ground rupture
b. ground pollution d. tsunami
11) Which of the following is NOT a sign of an impending tsunami? a. feeling a ground shaking c. seeing the water’s color change b. hearing a loud roaring sound d. seeing the water level drop
12) It is a tool which shows the areas where specific earthquake hazards are likely to happen and the severity of the expected impact such areas will experience. a. early warning device c. hazard map
b. earthquake hazard detector d. seismograph
13) Which of the following earthquake hazards cannot be prevented and everyone will experience during an earthquake?
a. ground rupture c. landslide
b. ground shaking d. liquefaction
14) If you observe the warning signs of a tsunami, which of the following should you do?
a. grab floating device and stay c. stay and just pray for it to go away b. move to a higher ground d. wait for tsunami to arrive for confirmation
15) Areas exposed to a Valley Fault System are at high risk of which earthquake hazard?
a. ground discoloration c. sinkhole
b. ground rupture d. tsunami
Key to answers on page 11
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What’s In (Review)
You’ve learned from the last lesson that impacts are associated to various hazards, affecting different exposed elements such as persons and properties. Knowing that hazards can cause danger to you and your family, it is important to know how the hazards work and how you can possibly prepare for them, in order to prevent or at least minimize the impact.
This lesson will introduce you to the first geological hazard you will be examining: earthquake hazards. Specifically, it is aimed at helping you analyze the effects of the different earthquake hazards, interpret different earthquake hazard maps, and recognize the natural signs of an impending tsunami. These knowledge and skills are helpful for you since Philippines, being situated in a tectonically active region of the Pacific Ring of Fire, is no stranger to earthquakes and tsunamis.
What’s New (Activity)
Activity 5.1: Historical Destructive Earthquakes and Tsunami
This activity will let you revisit some of the destructive earthquakes and tsunami that greatly affected several areas in the country and identify various impacts that they caused. Your answers will be useful in the succeeding activities.
1. Make a research online or interview older family members about 3 earthquakes that affected the country in the past. 2. Collect the following information: (a) date when the earthquake happened, (b) magnitude and intensity of the earthquake, (c) the epicenter and areas greatly affected by the earthquake, and (d) description of impacts of the earthquake. 3. Organize your answers using the table provided below. Date Epicenter & Magnitude & Description of Areas Affected Intensity Impacts 4. What words do you associate with earthquakes? Create a concept map about earthquakes using the diagram provided. |
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EARTHQUAKE 5. Next, make a research online or interview older family members about 2 incidents of tsunami that affected the country in the past. 6. Collect the following information: (a) date when the tsunami happened, (b) the location of event, and (c) description of major impacts of tsunami. 7. Organize your answers using the table provided below. Date Location of Event Major Impacts
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What Is It (Discussion)
5.1 EARTHQUAKE HAZARDS
Recall that earthquake is defined by PHIVOLCS as a weak to violent shaking of the ground produced by the sudden movement of rocks or rock materials below the earth’s surface. It could either be tectonic (generated by the sudden displacement along faults and plate boundaries) or volcanic (induced by rising lava or magma beneath active volcanoes). Regardless of the type, an earthquake is inevitably associated with hazards that could potentially cause damage to vulnerable and exposed elements. These are termed earthquake hazards.
Earthquake hazards, just like any other hazards, could possibly cause health impacts, physical and property destruction, social and economic disruption, and environmental damage. The most common earthquake hazards are: (a) ground shaking, (b) ground rupture, (c) liquefaction, (d) earthquake-induced landslides, and (e) tsunami. We’ll learn each hazard and their effects in this lesson.
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5.1.1 Ground Shaking
Ground shaking is basically the up-down and sideways motion felt during an earthquake. Different parts of the country will experience ground shaking at varying degrees depending on various factors, such as the magnitude of the earthquake, distance of one’s location from the fault that moved, orientation of fault rupture, bedrock type, and topography. If an earthquake produces a strong ground shaking, infrastructures can be severely damaged. Hanging and stacked objects could fall and cause physical injuries. Windows and glass doors may break. Persons standing can be destabilized and may be injured from falling.
5.1.2 Ground Rupture
Ground rupture is the visible displacement or deformation on the ground brought about by the movement of a fault. The movement may be as small as 0.5 meters and may have vertical and horizontal component. If a house or a structure is situated along a fault, it may experience ground rupture and may be destroyed if fissuring occurs.
5.1.3 Liquefaction
Liquefaction happens when a body of solid sediments starts to behave like liquid due to extremely intense shaking. It usually happens to sediments located near bodies of water. As a result, structures or buildings on top will either sink or tilt as the liquefied body of sediment can no longer support it due to changes in its properties.
5.1.4 Earthquake-induced Landslide
When the rocks and loose thin soil covering on the slopes of steep mountains are shaken during an earthquake, mass migration of these materials, termed as landslide, occurs. Earthquakes can trigger landslides by increasing the driving force than the resisting force. This results to erosion, burial, destruction of plants and properties, and blockage of roads and rivers.
5.1.5 Tsunami
When geological processes occur, like strong under-the-sea earthquakes, it often results to the production a series of giant waves greater than 5 meters, called tsunami. This could result to coastal erosion, flooding, damage to properties, and drowning of people.
It is important to note that a tsunami differ from a storm surge in terms of what is causing the waves. While a storm surge is caused by strong winds blowing the water on the surface of the sea, a tsunami is generated by disturbances in the seabed due to under-the-sea earthquakes and geological processes.
While the effects of earthquake hazards are quite fearsome, there is a way to prepare for them by knowing where they could possibly occur. The next lessons will focus on helping you recognize signs of an incoming tsunami and interpret a helpful tool, the earthquake hazard map.
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5.2 SIGNS OF AN IMPENDING TSUNAMI
Based on the stories of eyewitness and survivors of past tsunamis, the following are the natural signs of an impending tsunami:
1. Feeling an earthquake. If the ground shakes under your feet in a coastal region, a tsunami may have been caused by a strong undersea earthquake. However, you may not feel an earthquake if the event is far away.
2. Seeing ocean water disappear from the beach, bay or river. Before a tsunami arrives, water may recede from the shoreline before returning as a fast moving wall of water. If you notice the water is disappearing, tell your family and friends and prepare to move inland or to higher ground.
3. Hearing an unusual roaring sound. If you hear a loud roar approaching (a bit like a passenger jet or a train), tell your family and friends. It could be a tsunami approaching.
These signs are popularized as SHAKE-DROP-ROAR for better recall.
5.3 EARTHQUAKE HAZARD MAPS
From earlier lessons, you have learned that there are at least 5 earthquake hazards that need to be considered: ground shaking, ground rupture, liquefaction, earthquake-induced landslide, and tsunami. For years, experts have been observing them and the occurrences and impacts of earthquakes. From the observation of the past faults and earthquakes, behavior of seismic waves throughout the country, and site conditions, experts have produced accurate and detailed maps showing the areas where a certain specific earthquake hazards are likely to happen and the severity of the expected impact such areas will experience. Such earthquake hazard maps are useful for the purposes of designing safe infrastructures, planning
appropriate land usage, and preparing emergency mitigation and response. Each earthquake hazard has a corresponding hazard map: (a) ground shaking hazard map, (b) ground rupture hazard map, (c) liquefaction hazard map, (d) earthquake induced landslide hazard map, and (e) tsunami hazard map.
A hazard map has the basic parts: (i) Map Title – indicates what the map is all about; (ii) Legend – indicates details and meaning of the symbols used; and (iii) Scale – helps determine distances.
Earthquake hazard maps are available in your community’s Disaster Risk Reduction and Management Council. You can also access online the DOST PHIVOLCS site and DENR-MGB site.
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What’s More (Enrichment Activities)
Activity 5.2: Classifying Earthquake Impacts
This activity will let you classify the impacts of earthquakes.
1. Refer to your answers in Activity 5.1. Classify the impacts listed in the Description of Impacts column into their respective hazard categories. Use the table provided. Description of Impacts Earthquake Hazards present |
What I Have Learned (Generalization)
Complete the following sentences with your learnings in this module.
• I have learned to recognize the three natural signs of an impending tsunami. First, _________________________________________________________. Afterwards, ____________________________________________________. Then, ________________________________________________________. Once I observe these signs, I should ________________________________
_____________________________________________________________.
• I have learned to analyze the effects of the different earthquake hazards. Ground shaking causes __________________________________________ _____________________________________________________________. Ground rupture causes __________________________________________ _____________________________________________________________. Liquefaction can _______________________________________________ _____________________________________________________________. Earthquake-induced landslide may _________________________________ _____________________________________________________________. And tsunami can cause __________________________________________ _____________________________________________________________.
• I have learned to interpret different earthquake hazard maps. The basic parts of a hazard maps are _______________, _______________, and _______________. The hazards maps can be accessed by _____________ _____________________________________________________________. They are important because ______________________________________.
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What I Can Do (Application)
Activity 5.3: “To Do or Not to Do” during a Tsunami
This activity will let you distinguish between the good and bad practices in the event of a tsunami. Key to answers are on page 11.
1. Categorize the statements below as TO DO or NOT TO DO by writing the letter on the appropriate column in the table. a. If a big tsunami is approaching, you should move as far inland as you can and move to a higher area. b. If a small tsunami is approaching, you should get out of the water and wait until you hear it is safe to return. c. If a tsunami occurs, you should invite your family to go to the shore and witness together a once-in-a-lifetime event. d. If you observe giant sea waves are approaching your way but did not feel ground shaking, it should not bother you and just stay on the coastal area. e. If you observe the water level is receding and hear roaring sound but did not feel an earthquake, you should still proceed to far inland and a higher area. f. If you recognize the signs of an incoming tsunami early but others in the beach don’t, you should quickly inform them of the event and advise them to move to a higher area with you. g. If you are swimming with your family and you feel a strong earthquake, you should let them go to higher ground while you stay on the shore so that you can later tell them when it is safe to return. h. If you feel a high magnitude earthquake, you should first make sure that a tsunami is approaching by seeing if the ocean level drops and by hearing roaring sound before you proceed to a higher area. To do Not to do |
Activity 5.4: Interpreting Earthquake Hazard Maps
This activity will let you interpret an earthquake hazard map of your community and assess the possible impacts.
1. Secure a copy of your municipality’s Earthquake Hazard Maps. You can either email/chat your community’s officials or access DOST-PHIVOLCS/DENR-MGB website. Your teacher may also opt to provide you one. 2. Use the obtained map to assess you community’s exposure to earthquake hazards. 3. Determine the trace of the Valley Fault System. 3. Identify and mark the following in the map: (a) your house, (b) barangay hall, (c) schools, (d) hospitals/clinics, (e) public markets, and (f) important infrastructures (gymnasiums, bridges, covered courts, etc.). |
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4. Use a ruler or string to measure the distances of the marked areas from the trace of the Valley Fault System. 5. Determine whether any of the identified elements on your map fall within any of the identified hazard zones (ground shaking, ground rupture, liquefaction and earthquake-induced landslides). 6. Determine whether any of the identified elements at risk are transected by the Valley Fault System. Use the classification provided to assess the intensity of risk of each identified element. Hazard Intensity Ground Shaking High Moderate Low Ground Rupture High Moderate Low Induced Landslide High Moderate Low Liquefaction High Moderate Low Active Fault Transected Not Transected |
Assessment (Posttest)
Direction: Choose the letter of the best answer and write this on your answer sheet.
1) It is a tool which shows the areas where specific earthquake hazards are likely to happen and the severity of the expected impact such areas will experience. a. early warning device c. hazard map
b. earthquake hazard detector d. seismograph
2) Areas exposed to a Valley Fault System are at high risk of which earthquake hazard?
a. ground discoloration c. sinkhole
b. ground rupture d. tsunami
3) It is produced by sudden movement along the Earth’s faults and plate boundaries.
a. quibolic earthquake c. tsunamic earthquake
b. tectonic earthquake d. volcanic earthquake
4) It is the perceived strength of an earthquake based on relative effect to people and structures; generally higher near the epicenter.
a. intensity c. magnitude
b. level d. strength
5) __________ takes place when loosely packed, water-logged sediments at or near ground surface lose their strength in response to strong ground shaking. a. Ground rupture c. Liquefaction
b. Landslide d. Tsunami
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6) ___________ is the perceptible shaking of the surface of the Earth resulting from sudden release of energy in the Earth’s crust that creates seismic waves. a. Earthquake c. Sinkhole
b. Landslide d. Tsunami
7) It refers to the disruptive up-down and sideways motion experienced during an earthquake.
a. ground rupture c. liquefaction
b. ground shaking d. tsunami
8) It is the production a series of giant waves greater than 5 meters as a result of under-the-sea geological processes.
a. surfing waves c. tsunami
b. tidal wave d. wave
9) It is produced by movement of magma beneath.
a. laharic earthquake c. tectonic earthquake
b. seismic earthquake d. volcanic earthquake
10) A __________ is a fracture on which one body of rocks slide past another. a. bedrock c. magma
b. fault d. sinkhole
11) It is based on instrumentally derived information and correlated strength with the amount of total energy released at the earthquake’s point of origin. a. intensity c. magnitude
b. level d. strength
12) Which of the following is NOT a sign of an impending tsunami? a. feeling a ground shaking c. seeing the water’s color change b. hearing a loud roaring sound d. seeing the water level drop
13) Which of the following earthquake hazards cannot be prevented and everyone will experience during an earthquake?
a. ground rupture c. landslide
b. ground shaking d. liquefaction
14) If you observe the warning signs of a tsunami, which of the following should you do?
a. grab floating device and stay c. stay and just pray for it to go away b. move to a higher ground d. wait for tsunami to arrive for confirmation
15) Which of the following is NOT an earthquake hazard?
a. earthquake-induced landslide c. ground rupture
b. ground pollution d. tsunami
Key to answers on page 11
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Additional Activities
Activity 5.5: My Earthquake Hazards and Tsunami Signs Brochure
The following tasks will let you prepare a brochure that would serve as your information-education campaign material later as you share your learnings in this lesson to your family and community.
1. Create your own Earthquake Hazards brochure that contains information about what the earthquake hazards are and their impacts. Include a segment that informs about the warning signs of an impending tsunami. Write the details using your local language. You can also add some illustrations. Be sure that your brochure contains accurate information, creativity, and simple terms. Let the rubrics provided be your guide. Content --------------- 14pts Accuracy ------------- 8pts Clarity ----------------- 5pts Creativity ------------- 3pts TOTAL ---------------- 30pts |
Answers to Questions
PRETEST
b ) 15 b ) 10 c ) 5
b ) 14 c ) 9 d ) 4
b ) 31 c ) 8 a ) 3
c ) 12 b ) 7 b ) 2
c ) 11 b ) 6 a ) 1
ACTIVITY 5.3
d, g, h , c f b, e, , a
Not To Do To Do
POSTTEST
b ) 15 b ) 10 c ) 5
b ) 14 d ) 9 a ) 4
b ) 31 c ) 8 b ) 3
c ) 12 b ) 7 b ) 2
c ) 11 a ) 6 c ) 1
- END OF MODULE –
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REFERENCES
Bagtasa, G., Dinanala, J. D., Morante, K. A., Villegas, M. M., and Zarco, M. A. Disaster Readiness and Risk Reduction (Teaching Guide for Senior High School). Quezon City: Commission on Higher Education, 2013.
Dianala, J. D., Aurelio, M., and Tan, C. Disaster Reduction and Risk Management – Core Reader. Philippines: Department of Education-Bureau of Learning Resources, 2017
Martinez-Villegas, M. L. “Filipinos in Japan: Narratives of Experience from the March 11, 2011 Great East Japan Earthquake and Tsunami.” Journal of Disaster Research 10, no. 1 (2015): 135-144.
Philippine Institute of Volcanology and Seismology. “Earthquake and Earthquake Hazards [Flyer].” 2006. Accessed May 20, 2020.
http://www.phivolcs.dost.gov.ph/images/IEC/earthquake_hazards.pdf
Philippine Institute of Volcanology and Seismology. “PHIVOLCS Earthquake Monitoring.” 2008. Accessed May 20, 2020.
http://www.phivolcs.dost.gov.ph/index.php?option=com_content&view=article &id=38&Itemid=75
Philippine Institute of Volcanology and Seismology. “Tsunami Preparedness [Flyer].” 2011. Accessed May 20, 2020. http://www.phivolcs.dost.gov.ph/index.php? option=com_phocadownload&view=category&id=17:tsunami-flyer&Itemid=44
U.S. Geological Survey. “Earthquake Hazards 101 - the Basics.” 2015. Accessed May 20, 2020. http://earthquake.usgs.gov/hazards/about/basics.php
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