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Geography > Unit 9: Hazardous Environments > Flashcards

Unit 9: Hazardous Environments Flashcards

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1
Q

Divergent plate margins

A

Spreading
Constructive
Ridge
Volcanic activity

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2
Q

Convergent plate margins

A

Subduction
Destructive
Trench
Volcanic activity

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3
Q

Transform plate margins

A

Later sliding
Conservative
No effect of topography
No volcanic activity

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4
Q

General pattern of earthquakes and volcanoes

A

Generally follows a linear pattern along tectonic plate boundaries. Earthquakes are common at destructive (convergent), constructive (divergent) and transform boundaries. Volcanoes are concentrated along destructive and constructive boundaries. There are anomalies such as intraplate earthquakes and volcanic hotspots where activity occurs way from plate boundaries due to stresses within the plate or mantle plumes. These highlight the relationship between tectonic processes and surface features

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5
Q

Earthquake concentration along plate boundaries

A

Most earthquakes occur along tectonic plate boundaries where significant geological activity takes place

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6
Q

Destructive/convergent boundaries for earthquakes

A

Strong earthquakes are common at destructive boundaries where an oceanic plate subducts beneath a continental plate or another oceanic plate

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7
Q

Constructive/divergent boundaries for earthquakes

A

Earthquakes at constructive boundaries where plates move apart are less powerful and occur at mid ocean ridges

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8
Q

Transform boundaries for earthquakes

A

Frequent and sometimes severe earthquakes occur where plates slide past one another

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9
Q

Intraplate earthquakes

A

Only a small number of earthquakes occur caused by stresses within the plate

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10
Q

Subduction zones and deep earthquakes

A

The deepest and strongest earthquakes occur at subduction zones where one plate is forced deep into the mantle

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11
Q

Global distribution of volcanoes

A

Most are located along tectonic plate boundaries

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12
Q

Destructive/convergent boundaries for volcanoes

A

Common at destructive boundaries where an oceanic plate subducts beneath a continental or another oceanic plate

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13
Q

Constructive/divergent boundaries for volcanoes

A

Also form where plates move apart creating fissures for magma to rise

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14
Q

Hotspots and intraplate volcanoes

A

Some volcanoes form away from plate boundaries over mantle hotpots where plumes of magma rise through the crust

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15
Q

Subduction zones are explosive eruptions

A

Volcanoes at subduction zones often produce explosive eruptions due to magmas high viscosity and gas content forming steep sided stratovolcanoes

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16
Q

Shield volcanoes at divergent boundaries and hotspots

A

Divergent boundaries and hotspots often create broad shield volcanoes which have gentle slopes and less explosive eruptions

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17
Q

Tsunamis location

A

Occur mainly in tectonically active regions especially around subduction zones where one plate sinks beneath another. 90% of tsunamis have been in the Pacific. Underwater earthquakes, volcanic eruptions or landslides can displace large volumes of water generating powerful waves

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18
Q

How are island arcs formed

A

Formed at convergent plate boundaries where two tectonic plates collide and one plate (usually oceanic) is forced beneath the other through subduction. As the subducting plate sinks into the mantle it melts due to high temperatures and pressures creating magma. This magma rises to the surface through cracks in overriding plates forming a chain of volcanic islands. Over time these emerge above the oceans surface creating an arc shaped chain. As the plate descend into the mantle it bends and creates a curvature resulting in a bow-shaped chain of volcanoes

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19
Q

Where are island arcs found

A

Usually in oceans along subduction zones at convergent boundaries between two oceanic plates or between an oceanic or continental plate

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20
Q

What do island arcs look like

A

Typically form a curved or arc like shape. Often made up of volcanoes some of which are active giving them a rugged, mountainous appearance. Due to volcanic soil many are covered in dense, tropical vegetation. Near the concave side of the arc there is a deep ocean trench where the subduction occurs

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21
Q

How are hot sports formed

A

The earths core heats the surrounding mantle causing it to be less dense and rise in a column. As this plume reaches the base of the lithosphere the heat causes partial melting of the overlying rock creating magma. The magma rises through weaknesses in the crust and erupts on the surface forming volcanoes. As the plate moves over the stationary hotspot over time a chain of volcanic islands is formed. Often forms broad shield volcanoes. Do not form at plate boundaries but within tectonic plates

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22
Q

Where are hot spots found

A

Can be found in the middle of tectonic plates rather than along boundaries. They can occur in oceanic and continental settings

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23
Q

What do hot spots look like

A

Often form isolated chains of volcanic islands. These are typically shield volcanoes which have gentle slopes and wide bases. The islands get progressively older as they move away from the current active volcanoes. As the islands erode and sink over time some of the them become underwater mountains (seamounts)

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24
Q

How are mid-ocean ridges formed

A

Form at divergent plate boundaries where two tectonic plates are moving apart. As the plates separate, magma from the mantle rises through the gap creating new oceanic crust. This is sea floor spreading. This magma cools and solidifies at the ridge forming undersea volcanic mountains. Over time this pushes plates further apart expanding the basin

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25
Q

Where are mid-ocean ridges found

A

Located on the ocean floor where tectonic plates are diverging. They are the longest mountain ranges in the world

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26
Q

What do mid-ocean ridges look like

A

They are vast, submarine mountain ranges that can extend thousands of kilometres. At the centre of the ridge there is a deep rift valley where the plates are pulling apart. The ridge is a site of frequent volcanic activity as magma rises. Can be home to hydrothermal vents where superheated water and minerals spew from the ocean floor

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27
Q

Tsunamis (primary earthquake hazard)

A

Large waves generated by underwater earthquakes affecting coastal areas with flooding

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28
Q

Aftershocks (primary earthquake hazard)

A

Small tremors following the main earthquake causing further damage

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29
Q

Ground shaking (primary earthquake hazard)

A

The most immediate and widespread effect causing buildings to collapse and triggering landslides

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30
Q

Surface rupture (primary earthquake hazard)

A

Displacement along the fault line that can crack roads, railways, pipelines and buildings

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31
Q

Liquefaction (primary earthquake hazard)

A

Occurs when saturated soil temporarily loses its strength and behaves like a liquid causing sinking structures

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32
Q

Economic disruption (secondary earthquake hazard)

A

Long term effects from the destruction of businesses, transportation and infrastructure

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33
Q

Health crises (secondary earthquake hazard)

A

Broken sanitation systems and facility damage can cause disease outbreaks and strain healthcare systems

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34
Q

Flooding (secondary earthquake hazard)

A

Can occur from dam failure, broken water mains or blocked rivers due to landslides or debris

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35
Q

Fires (secondary earthquake hazard)

A

Damage to gas lines and electrical infrastructure can lead to fires

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36
Q

Social displacement (secondary earthquake hazard)

A

People may be forced to flee creating refugee crises

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37
Q

Landslides and rockfalls (secondary earthquake hazard)

A

Triggered by ground shaking or destabilisation of slopes leading to property and infrastructure destruction

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38
Q

Earthquake

A

A series of seismic vibrations or shock waves which originate from the focus

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39
Q

Focus

A

The point at which the plates release the tension or compression suddenly

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40
Q

Epicentre

A

The point on the earths surface directly above the focus

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41
Q

Seismology

A

The study of earthquakes and seismic waves that move through and around the earth. Seismologists study earthquakes and seismic waves

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42
Q

Seismic waves

A

The waves of energy caused by the sudden breaking of rock within the earth or an explosion. They are the energy that travels through the earth recorded on seismographs

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43
Q

Shallow vs deep focus

A

Earthquakes are classified as shallow, intermediate or deep depending on the location of the focus. Shallow focus earthquakes are the most damaging

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44
Q

Focus depth

A

Shallow = 0-70km
Intermediate = 70-350km
Deep = 350-670km
Intermediate and deep focus earthquakes occur only in subduction zones where cool rocks extend to great depths

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45
Q

Why do earthquakes happen?

A

Most are casued by the movement of tectonic plates
Reactivation of old fault lines that have been inactive for a long time
Subsidence as a result of deep mining
Pressure on surface rocks from water in large reservoirs
Underground disposal of liquid wastes
Underground nuclear testing and explosions
Mining and fracking
Increased crustal loading

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46
Q

Primary waves

A

The fastest moving type of wave and the first detected by seismographs. They are longitudinal and pus and pull the ground in the direction the wave is travelling, causing little damage. Can travel through solids and liquids

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47
Q

Secondary waves

A

Travel slower than P waves in the same direction but shake the ground perpendicular to the direction of wave travel. More dangerous because have a greater amplitude and produce vertical and horizontal motion of the ground surface. Can travel through solids not liquids

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48
Q

Surface waves

A

Are the slowest waves travelling along the surface of the earth made up of love and rayleigh waves

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49
Q

Love waves

A

Move back and forth horizontally and cause a lot of damage but can only travel through solids

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50
Q

Rayleigh waves

A

Cause vertical and horizontal ground motion. Can be the most destructive as they cause the ground to rise and fall as they roll past. Can travel through liquids and solids

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51
Q

Richter scale

A

Measures the magnitude of an earthquake showing the amount of energy released. It is a logarithmic scale so each whole number increase represents a 10x increase in amplitude and 32x more energy released. Developed in 1935 by Charles Richter used for smaller, local earthqyakes

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52
Q

Moment magnitude scale

A

A modern system used to measure the size of earthquakes. Considered more accurate than the Richter scale especially for large or distant events. It calculates the earthquakes moment which considers the area of the fault that slipped, the distance it moved and the rigidity of the earths crust measuring the total energy released. Is a logarithmic scale. Works consistently for earthquakes of all sizes and distances. Used for more precise and consistent comparisons worldwide

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53
Q

Mercalli scale

A

Measures the intensity of an earthquake based on its effects on people, buildings and the environment. Uses Roman numerals I to XII where I represents a tremor that is barely felt and XII shows total destruction. It is subjective as it depends on human observations rather than scientific instruments

54
Q

Tectonics and the global distribution of earthquakes affecting their impact

A

Most earthquakes do coincide with major plate margins. A number of earthquakes occur away from plate margins. Certain margins have a greater density of earthquakes. Earthquakes form a narrower spread at some plate margins. Those at destructive margins have a greater spread and affect more than constructive. Those places closer to destructive or transform margins are more at risk. Pressure builds at plate margins which when released causes an earthquake. A greater pressure builds at destructive and transform margins

55
Q

Causes of mid plate earthquakes

A

Referred stress release where stress built at a margin is relieved along a mid plate fault
Reservoir construction where increased weight and pre pressure reactivates faults
Water or oil abstraction altering underground pressures
Mining subsidence

56
Q

Earthquake magnitude and depth affecting their impacts

A

The stronger the earthquake the more serious its effects except magnitude alone is not responsible for the scale of a disaster. Shallow focus earthquakes cause a greater intensity of surface shaking and the greatest effects. Shallow earthquakes are associated with destructive margins where the subducting plate descends at an angle so stresses near the surface

57
Q

Nature of bedrock affecting earthquake impacts

A

Some materials are vulnerable to liquefaction causing building foundations to become unstable and slopes vulnerable to mass movement

58
Q

Population density affecting earthquake impacts

A

There is a large overlap between major earthquake zones and high population density. These conurbations are especially vulnerable due to densely packed buildings and raised freeways. 10% of the population are in earthquake zones

59
Q

Building and structural vulnerability affecting earthquake impacts

A

Most suffering results from building and structure collapse. In wealthy areas building materials and appropriate designs can minimise deaths but older properties remain vulnerable despite regulations. In poorer areas building design is inadequate and regulations are rarely enforced. In areas with rare earthquakes, precautions are limited so suffering is greater

60
Q

Extent of earthquake preparedness affecting their impacts

A

In wealthy areas with common earthquakes much is done to prepare. There are drills and people are informed. Emergency services and supplies are ready to cope with the aftermath. Preparation can reduce the scale of a disaster but could fail to live up to expectations. Poor countries are less prepared due to a lack of money to invest and earthquakes are perceived as infrequent problems when facing struggles of survival

61
Q

Levels of development affecting earthquake impacts

A

A poor country with less rigorous building standards and an inability to cope with the aftermath will suffer a greater loss of life, homelessness and livelihood. Richer MEDCs suffer less human loss but greater financial loss as insurance companies and governments fund re building programmes and compensation

62
Q

What is a tsunami?

A

A wave or series of waves generated by a sudden displacement of water. They have long wavelengths of up to 100km and there can be up to an hour between waves. They can travel up to 800km/h across the ocean over many thousands of kilometres

63
Q

Causes of tsunamis

A

There needs to be a vertical displacement of a body of water in the ocean. This is most commonly associated with earthquakes and volcanic eruptions especially along destructive plate margins where two plates are moving towards each other causing great build up of pressure. They can also be generated by underwater landslides, explosions and cosmic body impacts

64
Q

What happens as a tsunami approaches land?

A

Friction with a shallowing seabed slows the wave and causes it to rise and gain in height. Variations in offshore profiles and the configuration of the coastline will significantly affect the height of the wave. The highest tsunamis are due to a narrowing of the coast. Wave refraction will also affect a tsunamis orientation and height

65
Q

Effects of tsunamis

A

Waves tear apart homes and businesses
Materials and possessions are buried in mud
Fishing vessels are swept onshore
Diseases can spread rapidly due to a lack of safe water and sanitation
Lack of food and shelter
Fishing communities have no boats and communities dependent on tourists are deserted
Mental effects of deaths of family

66
Q

Behavioural responses to tsunamis

A

There can be several hours between an earthquake and a wave reaching land so people have time to respond by moving to safer ground. With increased technology and the use of satellites and computer modelling warnings can be issued. An increased understanding of wave mechanics enables scientists to be precise about the scale of waves. Public awareness and education are important. Local authorities need to have plans for the immediate aftermath such as with stores of emergency supplies and considering compromised transportation

67
Q

Structural responses to tsunamis

A

The cost of building seawalls along an entire coastline would be prohibitive and would have a significant impact on coastal systems. Tsunamis being relative rare in any one place makes this impractical

68
Q

Tsunami warning systems

A

Advisory: an earthquake has occurred which might generate a tsunami
Watch: a tsunami has been generated but it is over 2 hours from the area. Local officials should prepare for possible evacuation
Warning: a generated tsunami could cause damage so people are strongly advised to evacuate

69
Q

Factors determining tsunami destructiveness

A

Wave energy
Shape of coastline
Relief of coastline
Presence of natural defences
Demography
Lack of experience
Lack of or inadequate warning systems and evacuation plans

70
Q

Types of volcanoes

A

Shield: large, broad slopes, fluid lava flow
Composite: steep and symmetrical, explosive eruptions
Lava domes: small with steep sides, oozes viscous lava
Cinder cones: smallest, single vent, erupts cinders, ash and rocks

71
Q

Types of lava

A

Basaltic
Andesitic
Dacite
Rhyolite
Decreasing mobility so increasing explosivity

72
Q

Aa and pahoehoe lava flows

A

Aa lava flows have a rough and jagged surface while pahoehoe flows are smooth, ropy or billowy in texture. Aa flows are typically slower due to higher viscosity whereas pahoehoe flows are faster and more fluid due to lower viscosity. Aa forms when lava cools and solidifies quickly, breaking into fragments as it moves. Pahoehoe forms lava that remains hot and slows smoothly. Pahoehoe is hotter with a higher gas content making it more fluid. Aa is cooler and has less gas contributing to thicker behaviour

73
Q

Iceland eruptions

A

Characterised by persistent fissure eruption. Large quantities of basaltic lava build up vast horizontal planes

74
Q

Hawaiian eruptions

A

Involve more noticeable central activity. Runny, basaltic lava travels down the sides. Gases escape easily. Occasional pyroclastic activity occurs but is less important

75
Q

Strombolian eruptions

A

Characterised by frequent gas explosions blasting fragments of runny lava into the air to form cones. Very explosive with lots of pyroclastic rock. Marked by a white cloud of steam from the crater

76
Q

Vulcanian eruptions

A

Violent gas explosions blast plugs of sticky or cooled lava. Fragments build up into cones of ash and pumice. Occur when there is very viscous lava that solidifies rapidly after an explosion. Clears blocked vents and spew volcanic ash in atmopshere

77
Q

Vesuvian eruptions

A

Characterised by powerful blasts of gas pushing ash clouds to the sky. More violent with lava flows. Ash falls to cover surrounding areas

78
Q

Plinian eruptions

A

Gas rushes up through sticky lava and blasts ash fragments into the sky in an explosion. Violent eruptions create large gas clouds and thick volcanic debris. Gas clouds and lava can rush down slopes. Part of the volcano may be blasted away in the eruption

79
Q

Active volcanoes

A

A volcano that is currently erupting, has erupted recently or is likely to erupt in the near future

80
Q

Dormant volcanoes

A

A volcano that is not currently erupting but has erupted in the past and may erupt again in the future

81
Q

Extinct volcanoes

A

A volcano that is unlikely to erupt again because it has no more magma supply

82
Q

Primary impacts of volcanoes

A

Tephra
Pyroclastic flows
Lava flows
Volcanic gases
Ash

83
Q

Secondary impacts of volcanoes

A

Lahars
Flooding
Tsunamis
Volcanic landslides
Climate change

84
Q

Tephra

A

Solid material ejected from the crater. Vary from large volcanic bombs to fine ash particles

85
Q

Volcanic bombs

A

Volcanoes can blast rock fragments and cooling lava bombs at high speed. The blasts and bombs can destroy buildings and kill plants and animals. The bombs do not travel very far but are deadly in the blast zone

86
Q

Ashfalls

A

Ash from the volcano can travel long distances in the air and falls over a wide area

87
Q

Primary impacts of ashfalls

A

Composed of tiny fragments of rock and glass, blankets regions making air dangerous to breathe and reducing visibility. Inhaling ash can cause respiratory problems especially for those with pre existing conditions. Long term exposure leads to long damage. Can cause building collapse from weight and abrasive nature damages equipment posing risks to transportation or services

88
Q

Secondary impacts of ashfalls

A

Contaminated water is unsafe threatening health while coasted agriculture causes soil degradation, reducing crop yields and food supplies. Particles can clog drainage systems causing flooding. Clean up efforts are costly and time consuming

89
Q

Pyroclastic flows

A

Very hot and travel up to 450 mph. Gas charged, high velocity flows made up of gases and tephra. Normally hug the ground and travel downhill or spread laterally under gravity. Their speed depends upon the density of the current, the volcanic output rate and the gradient of the slope. A broad term for fast moving currents of hot gas, ash and volcanic material that flow down the slopes of a volcano

90
Q

Nuees ardentes

A

A specific type of pyroclastic flow, characterised by its dense, glowing, cloud like appearance and often formed from the collapse of an eruption column or volcanic dome. They are fast moving, hot pyroclastic flows composed of ash, gas and volcanic fragments. They resemble dense, turbulent clouds of glowing mertierla racing downslope. Can travel at speeds of 100-700km/h. Extremely hot, ranging from 200-700C

91
Q

How are nuees ardentes formed?

A

During a volcanic eruption, a column of hot ash and gas rises. If the column becomes too dense it collapses under its own weight creating a nuee ardente. When a volcanic dome (hardened mass of lava) becomes unstable it can collapse and release pyroclastic material downslope. A sudden release of pressure can violently eject material that forms a nuee ardente

92
Q

Lava flows

A

Streams of molten rock that pout or ooze from an erupting vent. Masses of molten rock can pour from volcanoes during an eruption. Lava flows are so hot they destroy everything in their path. Most are quite slow moving and not a threat to human life

93
Q

Volcanic gases

A

Include CO2, CO, hydrogen sulfide, SO2 and chlorine. The craters of many volcanoes can fill with rainwater forming lakes. Volcanic gases can seep up through the ground at collect at the bottom of lakes. When the water gets displaced the gases can seep out

94
Q

Lahars

A

A destructive volcanic mudflow composed of water, ash, rock and debris that travels rapidly down a volcanoes slope often triggered by eruptions, rainfall or melting ice

95
Q

Formation of lahars

A

Explosive eruptions can rapidly melt snow and ice on a volcanoes summit releasing large amounts of water that mix with volcanic ash and debris. Intense rain during or after an eruption can mobilise loose volcanic material creating fast moving mudflows. The sudden release of water from a volcanic lake or the collapse of unstable crater walls can trigger lahars

96
Q

Impact of lahars

A

Can bury roads, bridges and buildings under thick layers of mud and debris, disrupting transportation and access. Their fast flow can sweep away people, livestock and farmland causing fatalities and long term economic hardship. Can choke rivers with sediment leading to flooding, water contamination and the destruction of aquatic habitats

97
Q

Flooding

A

Caused by the melting of ice caps or glaciers by volcanic eruptions and lava flows

98
Q

Tsunamis with volcanoes

A

Usually caused by earthquakes but can be caused by large caldera forming volcanic eruptions

99
Q

Volcanic landslides

A

Landslides are common on volcanoes because their massive cones typically rise hundreds to thousands of metres above the surrounding terrain and are often weakened by the process that created them being the rise and eruption of molten rock. Each time magma moves toward the surface overlying rocks are shouldered aside as the molten rock makes room for itself often creating internal shear zones or over steepenidng one or more sides of the cone

100
Q

Climate change and volcanoes

A

The ejection of vast amounts of volcanic debris into the atmosphere can reduce global temperatures and is believed to have been an agent in past climate change vents

101
Q

Landslides

A

Occur due to earthquakes, volcanoes, floods or wildfires. The destruction depends on the speed of onset, speed of movement, slope angle, ground saturation and volume of material. Earthquakes can lead to liquefaction if flat land has a high water content. Saturated sediment loses strength undermining foundations, lowering the ground

102
Q

Primary impacts of earthquakes

A

Possessions broken
Building collapse
Air pollution
Infrastructure destroyed
Injuries
Missing persons
Buildings lost

103
Q

Secondary impacts of earthquakes

A

Rescue resources stretched
Psychological impacts
Homelessness
Lack of food and water
Lack of sanitation causing diseases
People leave areas

104
Q

Primary impacts of volcanoes

A

Ash and smoke in the air
Loss of light
Ash falls
Congestion from evacuation
Lava flows destroy infrastructure
Pyroclastic flows destroy villages and farms
Neighbourhoods lost

105
Q

Secondary impacts of volcanoes

A

Respiratory problems from ash
Homelessness
Decline in economy due to loss of agriculture and airport closures limiting aid
Overcrowding
Lack of food, water and sanitation
Psychological impacts

106
Q

Primary impacts of tsunamis

A

Loss of homes and boats
Injuries
Deaths
Building destruction
Flattened villages

107
Q

Secondary impacts of tsunamis

A

Homelessness
Psychological impacts
Lack of clean drinking water causing infection and disease
Loss of livelihoods
Lack of schooling

108
Q

After the impacts of hazards

A

New employment opportunities
International aid received
Building design and location improvements
Education of locals
Improved warning systems and government policies
Government compensation

109
Q

Volcanic eruption strength

A

Strength is measured by the Volcanic Explosive Index (VEI). Based on the amount of material ejected in the volcanic explosion, height of ash clouds and damage caused. Above 5 is very strong and 8 is a supervolcano

110
Q

Supervolcanoes

A

Can produce an eruption with an explosive force thousands of times greater than a regular volcanic eruption leading to global consequences. Much larger than regular volcanoes with eruption craters tend to hundreds of kilometres wide. Can drastically alter the climate and ecosystems. Eruptions are rare but have the potential to cause mass extinctions and climate change

111
Q

Risk

A

The probability of a hazard event causing harmful consequences

112
Q

Vulnerability

A

The geographic conditions that increase the susceptibility of a community to a hazard or the impacts of a hazard event

113
Q

Hazards vs disasters

A

A hazard refers to a potential event or phenomenon that has the capacity to cause harm to people, property or the environment. A disaster occurs when a hazard actually impacts vulnerable populations resulting in significant damage, disruption or loss of life. Without a degree of vulnerability a hazard does not become a disaster

114
Q

Perception of risk factors

A

Experience (people who have been in a similar disaster before will cope better)
Material well being (wealthy people will have more options available)
Personality (is the person a leader, follower or risk taking impacting reactions)

115
Q

Response options

A

Do nothing and accept the consequences of the hazard
Adjust to the situation of living in that area
Leave the area

116
Q

Factors impacting the level of adjustment to a hazard

A

Identification of hazards
Estimation of the risk of the hazard
An evaluation of the cost casued by the hazard

117
Q

Precondition stage of response

A

1: Lifestyle risks, routine safety measures, social construction of vulnerability, planned developments and emergency preparedness
2: Incubation period, erosion of safety measures, heightened vulnerability, signs and problems misread or ignored

118
Q

The disaster stage of response

A

3: Beginning of crisis, threat period, impending or arriving hazard, danger seen clearly, may allow warnings, flight or evacuation and pre-impact measures
4: The disaster, concentrated impacts, impaired or destroyed security, individuals and small groups cope as isolated survivors
5: Exposure of survivors, post impact hazards, delayed deaths
6: Rescue, relief, evacuation, shelter provision, clearing dangerous wreckage, organized response, national and international humanitarian efforts

119
Q

Recovery and reconstruction stage of response

A

7: Relief camps, emergency housing, residents and outsiders clear wreckage, salvage items, blame and reconstruction debates, disaster reports, evaluations, commissions of enquiry
8: Reintegration of damaged community with society, re-establishment of everyday life, similar to or different from pre disaster, continuing private and recurring communal grief, disaster related development and hazard reducing measures

120
Q

Managing the earthquake hazard

A

Better forecasting and warnings
Improved building design and location
Establishing emergency procedures

121
Q

Predicting and monitoring earthquakes

A

Small scale ground surface changes
Small scale uplift or subsidence
Ground tilt
Changes in rock stress
Micro earthquake activity
Anomalies in earths magnetic field
Changes in radon gas concentration
Changes in electrical resistivity of rocks
Requires detailed recording with specialist equipment and not reliable. Hard to be confident of exact time and location

122
Q

Methods of detecting earthquakes

A

Includes distortion of fences, roads and buildings as well as changes in water levels of boreholes. Strain can change the water holding capacity or porosity of rocks by opening cracks. Satellites can measures the position of points on the earths surface

123
Q

Difficulties in predication and risk assessment of earthqukes

A

Some earthquakes are irregular in time while other parts of the surface may continually slip and produce lots of small earthquakes. Different parts of a fault line may behave differently. Areas that don’t move are seismic gaps but areas with many small earthquakes may be less hazardous. The location of earthquakes is closely linked with the distribution of fault lines but timing is hard to predict. Previous patterns and frequencies have some prediction but size is hard to predict

124
Q

Earthquake monitoring equipment

A

Seismometer to record minor earthquakes
Magnetometer to record changes in earths magnetic field
Near surface seismometer to record larger shocks
Vibroseis truck to create shear waves to probe the earthquake zone
Strain meter to monitor surface deformation
Sensors in wells to monitor changes in groundwater levels
Satellite relays to relay data to weather stations
Laser survey equipment to measure surface movement

125
Q

Background of earthquakes

A

1.5 million people were killed by earthquakes in the 20th century. Most deaths are caused by collapsing buildings. 1/3 of the worlds largest cities are in earthquake prone areas. Earthquakes can’t be stopped so risks need to be minimised

126
Q

Seismic gap theory

A

Suggests that sections of active fault lines having not experienced significant earthquakes for a long time are gaps where stress is building making future events more likely. Over time as tectonic plates move stress accumulates along fault lines. Stress may not be released in a seismic gap increasing the risk of a major earthquake. They are used to aid earthquake preparedness and risk mitigation

127
Q

Countries preparing for earthquakes

A

Implement and enforce strict building regulations to ensure structures are designed to withstand seimsic activity. Establish well coordinated emergency plans including evacuation routes, communication strategies and resource allocation after. Raise awareness about earthquake preparedness through community training programmes, drills and information resources. Install advanced seismic monitoring and early warning systems to detect and alert of earthquakes to take protective measures. Reinforce essential facilities to ensure they are functional during and after an earthquake. Use seismic risk maps to guide land use decisions avoiding construction in high risk areas and promoting sustainable urban development

128
Q

Land use planning for earthquakes

A

Prohibit construction in areas prone to earthquakes like fault lines, unstable slopes and liquefaction zones to reduce damage and casualties. Implement land use zoning laws that limit high density developments in earthquake prone regions and prioritize open spaces for emergency shelters and evacuation routes. Require seismic risk assessments before approving major construction projects ensuring urban development is safe, sustainable and resilient

129
Q

Designing earthquake resistant buildings

A

Reinforced foundations
Base isolation systems
Shock absorbers
Flexible materials
Cross bracing and shear walls
Lightweight roofs and floors
Retrofitting older structures

130
Q

LEDC building designs

A

Quake-resistant houses are being built of straw. The compressed bales are held together by nylon netting between layers of plastic. Heavy concrete roofs collapse on many homes, sheet metal roofs on wooden trusses are more resistant. Small, regularly spaced windows create fewer weak spots but walls are not properly reinforced. Reinforcing rods can be made of natural materials or plastic mesh. Brick walls can be framed and connected to the roof by corner columns and a crown beam of reinforced concrete. Tyres filled with stones and sand between floor and foundation can be cheap ground motion absorbers

Geography (30 decks)

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