natural hazards

1.0x

natural hazards

Created 3 years ago

Duration 0:27:28
lesson view count 172
Select the file type you wish to download
Slide Content
  1. Natural Hazards

    Slide 1 - Natural Hazards

  2. Introduction to Natural Hazards

    Slide 2 - Introduction to Natural Hazards

    • What is a natural hazards?
    • Earth processes (involving the lithosphere, hydrosphere & atmosphere) that, upon interaction with human activity, cause loss of life and property
    • It is important to understand the human element
    • without it, there would be no hazard
    • because of it, the science of natural hazards becomes more important every year
    • mitigation: reduction/prevention
    • geo-process
    • humanprocess
    • Hazardousconditionor result
  3. The Earth’s population is increasing

    Slide 3 - The Earth’s population is increasing

    • more people living in hazard-prone areas
    • populations are becoming hyper-concentrated
    • consumption of resources
    • examples:
    • today there are 6 billion people on Earth ( ~ 50% live in cities)
    • by 2025, there will be ~8 billion people (~ 66% in cities)
    • of these cities, 40% are coastal
    • prone to severe storm and tsunami damage
    • and a large majority lie in areas subject to other geohazards (for example volcanoes and earthquakes)
    • Why is the human element so critical?
  4. CANNOT stop the geologic processes

    Slide 5 - CANNOT stop the geologic processes

    • CANNOT stop the population growth/expansion
    • Therefore, we must try to reduce the hazards through:
    • scientific study
    • population education
    • changes in engineering/building practices
    • management plans and hazard response scenarios
  5. Types of Natural Hazards

    Slide 6 - Types of Natural Hazards

    • Volcanoes, floods, earthquakes, tornadoes, tsunamis, etc.
    • can act adversely on human processes
    • can occur:
    • without warning (e.g. earthquakes)
    • with warnings (precursors) (e.g. satellite monitoring of cyclone tracks, or the presence of ground deformation at a volcano before an eruption)
  6. To help mitigate the hazard we need to know:

    Slide 7 - To help mitigate the hazard we need to know:

    • Frequency vs. Magnitude
    • F: how often a given event occurs in a certain region
    • M: how powerful (amount of energy released) an event is
    • for example, high M hazards happen with low F, but are much more destructive
    • Scope
    • S: area affected by a given hazard
    • local: landslides, floods, earthquakes, fire …
    • regional: tsunamis, volcanoes, larger earthquakes, cyclones …
    • global: large volcanoes, global warming, meteorite impacts …
  7. Earthquakes and Tsunamis

    Slide 8 - Earthquakes and Tsunamis

  8. What is an Earthquake?

    Slide 9 - What is an Earthquake?

    • Ground movement caused by the sudden release of seismic energy due to tectonic forces.
    • The focus of an earthquake is the actual location of the energy released inside the Earth’s crust.
    • The epicentre is the point on the Earth’s surface directly above the focus.
  9. Why do earthquakes occur?

    Slide 10 - Why do earthquakes occur?

    • Seismic energy is usually caused by the brittle failure (fracturing) of rocks under stress.
    • This commonly occurs due to movement along tectonic plate boundaries
    • Figure showing the distribution of earthquakes around the globe
  10. Earthquake Magnitude

    Slide 11 - Earthquake Magnitude

    • Magnitude
    • Earthquake Effects
    • Approx. number each year
    • < 2.5
    • Usually not felt, but recorded
    • 900,000
    • 2.5-5.4
    • Often felt, only minor damage
    • 30,000
    • 5.5-6.0
    • Slight damage to buildings and other structures
    • 500
    • 6.1-6.9
    • May cause a lot of damage in very populated areas
    • 100
    • 7.0-7.9
    • Major earthquake. Serious damage.
    • 20
    • > 8.0
    • Great earthquake. Can be totally destructive near the epicentre.
    • 1 every 5-10 years
  11. San Francisco - Great Earthquake

    Slide 12 - San Francisco - Great Earthquake

    • Magnitude 7.7 - 8.3
  12. Earthquake Hazards

    Slide 13 - Earthquake Hazards

    • These are important hazards to understand:
    • the natural hazard that on average kills the highest number of people per year (> 1 million during the past century)
    • commonly strikes without warning
    • no time for evacuation
    • not a predictable trend to earthquake numbers, magnitude or location
    • 1000's of large earthquakes every year
    • ~ 20 are > M7.0 and these account for 90% of the energy released and 80% of all the fatalities
  13. How do we mitigate the hazard from earthquakes?

    Slide 15 - How do we mitigate the hazard from earthquakes?

    • Reinforce buildings
    • Education
    • Disaster plan
  14. Earthquakes and Tsunami’s

    Slide 16 - Earthquakes and Tsunami’s

    • An earthquake under the ocean has the potential to form a tsunami.
    • The earthquake must vertically displace overlying water (extensional or compressional faults - not transform)
    • Extension
    • Compression
    • Transform
  15. How does an earthquake form a tsunami?

    Slide 17 - How does an earthquake form a tsunami?

  16. 2004 South Asian Boxing Day event

    Slide 18 - 2004 South Asian Boxing Day event

    • Biggest earthquake in 40 years!
    • Magnitude 9.2
    • 150 km off the west of Northern Sumatra
    • Generated a disastrous tsunami in 12 countries
  17. The earthquake occurred at a convergent tectonic plate boundary (subduction zone)

    Slide 19 - The earthquake occurred at a convergent tectonic plate boundary (subduction zone)

    • An estimated 1,600 km (994 miles) of faultline slipped about 15 m (50 ft)!
    • The earthquake released 20 x 1017 Joules of energy
    • Equivalent to:
    • 475,000,000 kg of TNT
    • 23,000 Hiroshima atomic bombs!
    • Second largest recorded earthquake
  18. Tsunami

    Slide 20 - Tsunami

    • Animations of the Boxing Day tsunami showing how the tsunami radiated from the entire length of the 1,600 km (994 miles) rupture.
    • Above: Countries most effected by the tsunami
  19. A village near the coast of Sumatra lays in ruin after the tsunami.

    Slide 21 - A village near the coast of Sumatra lays in ruin after the tsunami.

  20. How do we mitigate the hazard from tsunamis?

    Slide 22 - How do we mitigate the hazard from tsunamis?

    • Monitoring
    • process is very technology-intensive
    • high costs for many poorer countries
    • often no technology available to monitor local tsunamis
    • for example,
    • Papua New Guinea has no monitoring stations
    • reliant on the Pacific Tsunami Warning Center
    • tsunami in 1998 was not detected
  21. Building restrictions in hazard prone areas

    Slide 23 - Building restrictions in hazard prone areas

    • In Hawaii, Hilo harbor and downtown was destroyed by the tsunamis of 1946 and 1960
    • The town is now rebuilt on higher ground and the devastated area is a park
    • How do we mitigate the hazard from tsunamis?
  22. Seawall construction

    Slide 24 - Seawall construction

    • cause early wave breaking
    • prevent wave run up into urban areas
    • How do we mitigate the hazard from tsunamis?
  23. Education

    Slide 25 - Education

    • warning systems
    • evacuation plans
    • general understanding of the hazards involved
    • Punishment
    • From God
    • 45%
    • Natural event
    • 35%
    • Bomb 20%
    • Population reaction: Papua New Guinea (1998)
    • How do we mitigate the hazard from tsunamis?
  24. Tropical Storms

    Slide 26 - Tropical Storms

  25. Same Storm - Different Name

    Slide 27 - Same Storm - Different Name

  26. Tropical Cyclones

    Slide 28 - Tropical Cyclones

    • Background:
    • Can be deadly!
    • For example, in 1991 a large cyclone in Bangladesh killed >138,000 people in just two days!
  27. Most widespread destructive weather hazard

    Slide 29 - Most widespread destructive weather hazard

    • For example: Hurricane Floyd (1999)
    • only a moderate level hurricane
    • caused US$5.6 billion in damage in the Bahamas and North Carolina (USA) and 57 fatalities
    • Tropical Cyclones
    • (Left) Three different cyclones spinning over the western Pacific Ocean on August 7, 2006.
  28. How do cyclones form?

    Slide 30 - How do cyclones form?

    • The above figure shows how cyclones form. The green arrows show where warm air is rising. The red arrows indicate where cool air is sinking.
  29. Cyclone Categories

    Slide 31 - Cyclone Categories

    • Category
    • Wind Speed (mph)
    • Damage at Landfall
    • Storm Surge (feet)
    • 1
    • 74-95
    • Minimal
    • 4-5
    • 2
    • 96-110
    • Moderate
    • 6-8
    • 3
    • 111-130
    • Extensive
    • 9-12
    • 4
    • 131-155
    • Extreme
    • 13-18
    • 5
    • > 155
    • Catastrophic
    • 19+
    • The Saffir-Simpson Hurricane Scale
  30. Hurricane Katrina

    Slide 32 - Hurricane Katrina

    • Hurricane Katrina was the most costly and most deadly hurricane in the history of the USA.
    • Category 5
    • At least 1,836 fatalities
    • Damage estimated at US$ 81.2 billion
  31. Slide 33

    • Hurricane Katrina
  32. What damage is produced?

    Slide 34 - What damage is produced?

    • Storm Surge
    • water that is pushed toward the shore by the force of the cyclone winds.
  33. What damage is produced?

    Slide 35 - What damage is produced?

    • Wind
    • responsible for the loss of power and utilities
    • wind damage affects larger areas than surge
    • flying debris
    • tree loss
  34. What damage is produced?

    Slide 36 - What damage is produced?

    • Flying debris
    • debris propelled at high speeds
  35. How do we mitigate the hazard from a cyclone?

    Slide 37 - How do we mitigate the hazard from a cyclone?

    • Monitoring
    • early warning systems
    • Infrastructure
    • cyclone walls
    • communal shelters
    • Education and planning
  36. Natural Hazards Summary

    Slide 38 - Natural Hazards Summary

    • Graph showing the number of deaths per year due to natural hazard events
  37. Reference

    Slide 39 - Reference

    • University of Bristol created the slides and presentation material.