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Natural Hazards 2„Nature to be commanded, must be obeyed“           (Francis Bacon, 1561-1626)             W. Eberhard Fal...
Natural Processes                    2
Driving forces behind natural processes•  There are three fundamental phenomena that drive all natural   processes:   –  r...
Radioactive decay in the environment•  It ‚powers‘ the sun•  Solar radiation causes the movements in the atmosphere (=   w...
Radioactive decay and geology•  It keeps the Earth‘s interior hot•  Without the decay heat, the Earth would have cooled do...
Gravity•    Drives the surface water flow from the mountains to the sea•    Drives the groundwater flow (pressure differen...
Rotational Inertia•  Causes, together with gravity, the tidal waves in the oceans                                         ...
Overview: Natural Hazards                            8
Hazard classification by root cause•  Endogenic    –  having their root in processeses in the Earth‘s interior•  Exogenic ...
Normal processes vs. catastrophic events•  Many exogenic, e.g. weather-related, processes occur regularly   and do not pos...
Endogenic hazards•  earthquakes•  volcanic phenomena•  tsunamis•  eustasis related phenomena•  natural radioactivity      ...
Exogenic hazards•  particularly relevant in high-energy environments   – mountain areas   – coastal areas   – river valley...
Weather-related hazards•  storms•  heavy rainfall•  hail•  snow•  severe frost•  severe heat•  droughts                   ...
Water-related hazards•    inundations•    (flash)floods•    avalanches•    tidal phenomena•    rogue ocean waves          ...
Geology-related hazards•    torrents•    mud flows•    rock falls•    landslides•    cave-ins•    permafrost-related      ...
Extraterrestrial hazards•  magnetic storms•  meteorite impacts                                        16
Endogenic hazards                    17
Earthquakes              18
Causes•  The Earth‘s crust is made up of numerous plates that slowly   move due to convections in the mantle•  Slow moveme...
Plate tectonics                  20
Tectonic plates                  21
Tectonic plates: animation                             22
Global distribution of earthquakes                                     23
Phenomenology•  Earthquakes generate different types of waves•  The strength and characteristics   of these waves can be r...
Mercalli vs.Richter Scale                            25
Seismographs and seismograms•  The seismograph utilises the inertia of a mass (e.g. a heavy   metal ball) relative to the ...
Earthquake hazardsDirect hazards•  Total or partial collapse of structures•  Falling debris and dust from rubble•  Transpo...
Earthquake impacts•  Total or partial   destruction of structures•  Blockage or interruption   of transport systems•  Inte...
Can they be predicted ?•  Science cannot yet predict earthquakes as to time or location   of their occurrence•  We can onl...
Mitigation measures•  Measures and strategies to   mitigate the effects and   impacts•  Earthquake resistant   buildings/ ...
Emergencypreparedness               31
Earthquakes - socio-economic impactAfter the event•  Desaster relief costs•  Lost economic opportunities•  Loss of land-us...
Volcanoes            33
What is a volcano ?•  An opening, or rupture, in the Earths crust that allows hot   magma, ash and gases to escape from be...
Typical occurence of volcanoes                                 35
The classical volcano: Stratovolcano•    Examples are Vesuvius, Aetna, Stromboli, Fuji                                    ...
Volcano hazards                  37
Arctic Vulcanos•    Sub-glacial vulcanos can pose the added risk of causing glacier     surges, e.g. on Iceland           ...
Volcanic eruption impacts•  Earthquakes•  Lava/mud flows destroy houses /   infrastructure•  Pyroclastic flows (up to 700 ...
Forecasting volcanic activities•  Most volcanoes (on land) and zones with volcanic activity are   well known•  These zones...
Volcanic risk mitigation•  Mapping of hazard/danger zones•  Land-use restriction in danger zones•  Emergency preparedness ...
Mapping hazard zones                       42
Socio-economic impacts•  Cost of mitigation measures•  Cost of emergency relief operations•  Cost of re-building houses an...
Tsunamis           44
The Japan tsunami on 11 March 2011                                     45
The Japan tsunami on 11 March 2011                                     46
What is a tsunami ?                      47
Mechanisms of tsunami generation•  Displacement of rock   masses cause displacement   of water                            ...
The travel of the tsunami of 26/12/2004                                          49
Tsunami early warning systems•  Following the tsunami that hit various regions around the Indian   Ocean on 26/12/2004, th...
Tsunami emergency preparedness                                 51
Tsunami risk maps                    52
Socio-economic impacts•  Cost of mitigation measures•  Cost of emergency relief operations•  Cost of re-building houses an...
Isostatic processes                      54
Definition•  Can have endogenic and/or exogenic causes•  A collection of processes that result in changes of the mean sea ...
Mean sea level•  Local mean sea level (LMSL) is defined as the height of the sea   with respect to a land benchmark, avera...
Isostatic rebound•  The continental crust floats on top of the mantle•  Changes in load on the continents results in varia...
Large-scale uplift of continents•  In some areas accompanied   by subsidence of   neighbouring areas•  For instance, The  ...
Hazards and impacts•  Slow, long-term movements in the order of 0.1 to 10 mm/year•  Rising areas:     – Receding coastline...
Next lesson•  Natural radioactivity  •  Exogenic hazards                           60
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Natural hazards 2-2013

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Transcript of "Natural hazards 2-2013"

  1. 1. Natural Hazards 2„Nature to be commanded, must be obeyed“ (Francis Bacon, 1561-1626) W. Eberhard Falck eberhard.falck@uvsq.fr 1
  2. 2. Natural Processes 2
  3. 3. Driving forces behind natural processes•  There are three fundamental phenomena that drive all natural processes: –  radioactive decay –  gravity –  the Earth‘s rotational inertia•  They cause/drive mass and energy flows throughout the natural environment•  Neither of these processes can be stopped or controlled by us humans 3
  4. 4. Radioactive decay in the environment•  It ‚powers‘ the sun•  Solar radiation causes the movements in the atmosphere (= wind) due to differential heating of different surfaces (e.g. water, land)•  Solar radiation causes evaporation and (indirectly) evapotranspiration from plants 4
  5. 5. Radioactive decay and geology•  It keeps the Earth‘s interior hot•  Without the decay heat, the Earth would have cooled down in about 30,000 years (Lord Kelvin)•  The heat flow from the earths drives phenomena such as – vulcanism - earthquakes – plate tectonics - orographic changes 5
  6. 6. Gravity•  Drives the surface water flow from the mountains to the sea•  Drives the groundwater flow (pressure differences due to different elevation)•  Causes eroded material to move downwards•  ‚Mountains‘ are a higher degree of order - according to the 2nd law of thermodynamics this order will dissipate 6
  7. 7. Rotational Inertia•  Causes, together with gravity, the tidal waves in the oceans 7
  8. 8. Overview: Natural Hazards 8
  9. 9. Hazard classification by root cause•  Endogenic –  having their root in processeses in the Earth‘s interior•  Exogenic –  having their root in processes above ground•  Extraterrestrial –  e.g. meteorite impacts 9
  10. 10. Normal processes vs. catastrophic events•  Many exogenic, e.g. weather-related, processes occur regularly and do not pose any hazards•  Changes in intensity, in timing or co-occurence of several phenomena can lead to catastrophic events –  heavy rainfall after a long dry seasons can lead to flooding or mud- slides –  heavy rainfall in several different regions of the same catchment area can lead to flooding –  prolonged wet weather can lead to mud-slides•  Normal events can trigger chains of events that finally lead to catastrophic events 10
  11. 11. Endogenic hazards•  earthquakes•  volcanic phenomena•  tsunamis•  eustasis related phenomena•  natural radioactivity 11
  12. 12. Exogenic hazards•  particularly relevant in high-energy environments – mountain areas – coastal areas – river valleys – because of •  high relief energy, i.e. steep slopes, altitude differences •  lack of protection from wind, waves etc. •  tidal forces•  climatic changes/variations – natural or human induced – change the dynamic equilibria in nature – humans have arranged themselves with a particular state of nature, which is changing later 12
  13. 13. Weather-related hazards•  storms•  heavy rainfall•  hail•  snow•  severe frost•  severe heat•  droughts 13
  14. 14. Water-related hazards•  inundations•  (flash)floods•  avalanches•  tidal phenomena•  rogue ocean waves 14
  15. 15. Geology-related hazards•  torrents•  mud flows•  rock falls•  landslides•  cave-ins•  permafrost-related 15
  16. 16. Extraterrestrial hazards•  magnetic storms•  meteorite impacts 16
  17. 17. Endogenic hazards 17
  18. 18. Earthquakes 18
  19. 19. Causes•  The Earth‘s crust is made up of numerous plates that slowly move due to convections in the mantle•  Slow movements occur along other fault zones in the crust•  The frictional energy built up is released spasmodically - an earthquake•  Small earthquakes can also occur due to volcanic activity•  Sometime earthquakes have an anthropogenic origin: e.g. collapsing underground mines•  Large earthquakes occur about once a year•  Small earthquakes occur about once an hour 19
  20. 20. Plate tectonics 20
  21. 21. Tectonic plates 21
  22. 22. Tectonic plates: animation 22
  23. 23. Global distribution of earthquakes 23
  24. 24. Phenomenology•  Earthquakes generate different types of waves•  The strength and characteristics of these waves can be recorded by seismographs•  From these measurements their location, the focus and the epicentre, can be determined•  The strength of an earthquake can be measured by magnitude and intensity•  The Richter scale measures the energy of the seismic waves (open logarithmic scale)•  The Mercalli scale measures the intensity or effect on the surface of the earth (descriptive scale) 24
  25. 25. Mercalli vs.Richter Scale 25
  26. 26. Seismographs and seismograms•  The seismograph utilises the inertia of a mass (e.g. a heavy metal ball) relative to the moving ground 26
  27. 27. Earthquake hazardsDirect hazards•  Total or partial collapse of structures•  Falling debris and dust from rubble•  Transportation casualties due to collapse of bridges etc.•  Floods from collapsed dams or river banks•  Landslides and soil liquefaction•  TsunamiesIndirect Hazards•  Fires•  Release of hazardous material•  Electrocution•  Exacerbation of pre-existing hazardous situations 27
  28. 28. Earthquake impacts•  Total or partial destruction of structures•  Blockage or interruption of transport systems•  Interruption of water, gas and electricity supplies•  Breakage of sewage systems•  Interruption of land-use due to landslides or inundation 28
  29. 29. Can they be predicted ?•  Science cannot yet predict earthquakes as to time or location of their occurrence•  We can only predict probabilities for regions and time spans•  For instance, the United States Geological Survey (USGS) calculates a probability of 67% for a major earthquake to occur in the San Francisco area within the next 30 years•  Research to understand possible warning signals is ongoing•  ‚Urban myths‘: –  Earthquake weather/season –  Animals or certain people can sense an oncoming earthquake 29
  30. 30. Mitigation measures•  Measures and strategies to mitigate the effects and impacts•  Earthquake resistant buildings/ infrastructure –  Lightweight construction –  Cross-bracing –  Decoupling –  High-strength door-frames –  Brick buildings are unsuitable•  Emergency preparedness•  Behavioural advice, e.g. „drop-cover-hold on“ (USA) 30
  31. 31. Emergencypreparedness 31
  32. 32. Earthquakes - socio-economic impactAfter the event•  Desaster relief costs•  Lost economic opportunities•  Loss of land-use due to landslides etc.•  Cost of rebuilding houses and infrastructure•  Disruption of societies•  Health impacts due to traumatisation and poorer healthcarePrecautionary measures•  Emergency preparedness costs•  Higher cost of safer building practices / retrofitting•  People / companies avoid earthquake zones - lost employment / economic opportunities 32
  33. 33. Volcanoes 33
  34. 34. What is a volcano ?•  An opening, or rupture, in the Earths crust that allows hot magma, ash and gases to escape from below the surface•  Volcanoes occur –  along plate boundaries –  above mantle plumes (hot spots) within plates –  as non-hotspot intraplate volcanism where a thinning of the Earth‘s crust occurs 34
  35. 35. Typical occurence of volcanoes 35
  36. 36. The classical volcano: Stratovolcano•  Examples are Vesuvius, Aetna, Stromboli, Fuji 36
  37. 37. Volcano hazards 37
  38. 38. Arctic Vulcanos•  Sub-glacial vulcanos can pose the added risk of causing glacier surges, e.g. on Iceland 38
  39. 39. Volcanic eruption impacts•  Earthquakes•  Lava/mud flows destroy houses / infrastructure•  Pyroclastic flows (up to 700 km/h, 1000°C) cannot be escaped•  Volcanic bombs•  Ash rain suffocates animal and plant life•  Large-scale eruptions eject ash into the strathosphere, where it can circulate for years and change the global climate (e.g. Krakatau, 1883)•  Tsunamis•  Poisonous and/or suffocating exhalations (H2S, SO2, CO2)•  Aerosols causing health problems•  Acid precipitation•  Glacier surges and melt-water torrents 39
  40. 40. Forecasting volcanic activities•  Most volcanoes (on land) and zones with volcanic activity are well known•  These zones are monitored•  Monitoring for seismic activity•  Precision geodesy to detect surface distortions•  Monitoring of effluent gas composition•  However, predicting the precise period for an eruption is difficult with the risk of false alarms or too late evacuation 40
  41. 41. Volcanic risk mitigation•  Mapping of hazard/danger zones•  Land-use restriction in danger zones•  Emergency preparedness plans•  Monitoring seismic/volcanic activities•  Evacuation when eruptions are iminent 41
  42. 42. Mapping hazard zones 42
  43. 43. Socio-economic impacts•  Cost of mitigation measures•  Cost of emergency relief operations•  Cost of re-building houses and infrastructure•  Cost of reforestation•  Cost of slope stabilisation measures•  Loss of farmland•  Exacerbated health problems due to poorer healh care and exposure to health hazards (e.g. dust)•  Disruption of economic activities (e.g. the Philipine GDP fell by 3% in the years after the Mt. Pinatubo eruption)•  Disruption of social life•  But also benefits, such as geothermal energy on Iceland 43
  44. 44. Tsunamis 44
  45. 45. The Japan tsunami on 11 March 2011 45
  46. 46. The Japan tsunami on 11 March 2011 46
  47. 47. What is a tsunami ? 47
  48. 48. Mechanisms of tsunami generation•  Displacement of rock masses cause displacement of water Before the earthquake•  Root causes can be –  earthquakes, –  seabed slides –  volcanic eruptions Earthquake –  cliff collapse –  iceberg calving Tsunami spreads out 48
  49. 49. The travel of the tsunami of 26/12/2004 49
  50. 50. Tsunami early warning systems•  Following the tsunami that hit various regions around the Indian Ocean on 26/12/2004, the efforts to set up early warning systems were considerably intensified.•  Early warning systems integrate the world-wide network of seismic stations with oceanic observation stations•  Like earthquakes, tsunamis cannot be predicted, but there are often several hours before a tsunami hits a coast and its spreading can be predicted 50
  51. 51. Tsunami emergency preparedness 51
  52. 52. Tsunami risk maps 52
  53. 53. Socio-economic impacts•  Cost of mitigation measures•  Cost of emergency relief operations•  Cost of re-building houses and infrastructure•  Cost of re-building coastal infrastructure•  Loss of fishing grounds and infrastructure, e.g. fishfarms•  Exacerbated health problems due to poorer healh care•  Disruption of economic activities•  Disruption of social life 53
  54. 54. Isostatic processes 54
  55. 55. Definition•  Can have endogenic and/or exogenic causes•  A collection of processes that result in changes of the mean sea level•  The mean sea level depends on the volume of the oceanic water•  The mean sea level depends on the topography of the ocean floors•  The topography of the ocean floors has changed significantly over geological timescales•  Isostatic rebound following the ice-age is a major mechanism e.g. in Northern Europe 55
  56. 56. Mean sea level•  Local mean sea level (LMSL) is defined as the height of the sea with respect to a land benchmark, averaged over a period of time (such as a month or a year) long enough that fluctuations caused by waves and tides are smoothed out 56
  57. 57. Isostatic rebound•  The continental crust floats on top of the mantle•  Changes in load on the continents results in variations in ‚draft‘ and dipping•  The appearance and retreat of continental ice sheets are such a change in load before glaciation during glaciation after glaciation 57
  58. 58. Large-scale uplift of continents•  In some areas accompanied by subsidence of neighbouring areas•  For instance, The Netherlands are sinking 58
  59. 59. Hazards and impacts•  Slow, long-term movements in the order of 0.1 to 10 mm/year•  Rising areas: – Receding coastline – Drying-up of harbours•  Subsidence areas: – Increasing probability of flooding – Increase of coastal erosion – Need to improve coastal defence measures – Considerable socio-economic impact e.g. in the Netherlands – Salination of near-coast groundwaters 59
  60. 60. Next lesson•  Natural radioactivity •  Exogenic hazards 60
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