Natural hazards earthquakes


Published on

  • Be the first to comment

  • Be the first to like this

No Downloads
Total Views
On Slideshare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide

Natural hazards earthquakes

  1. 1. Earthquakes<br />Prof. David Alexander<br />Global Risk Forum Davos<br />
  2. 2. Physical<br />aspects<br />
  3. 3. The causes of seismicity:-<br /><ul><li>tectonic activity caused by</li></ul>stresses in the earth's crust<br /><ul><li>volcanic activity resulting in stress</li></ul>caused by the injection of magma<br />into the crust (volcanosiesmicity).<br />
  4. 4. A typical year of earthquakes (1996)<br />Magnitude<br />
  5. 5. Seismology: the study of<br />elastic (seismic) waves<br />The properties of waves:<br /><ul><li>wavelength and frequency</li></ul>(number per unit of time)<br /><ul><li>amplitude (vertical distance</li></ul> from crest to trough)<br /><ul><li>phase difference.</li></li></ul><li>crest<br />AMPLITUDE <br />trough<br />WAVELENGTH<br /> (per unit time = frequency) <br />PHASE DIFFERENCE <br />
  6. 6. Strong motion of the ground:-<br /><ul><li>duration(seconds)
  7. 7. frequencies present in the waves
  8. 8. maximum amplitude of the waves
  9. 9. dispersion if wave energy with</li></ul>distance from the point of generation<br /><ul><li>maximum velocity
  10. 10. maximum acceleration.</li></li></ul><li>Bracketed duration: the period of<br />time in which seismic shaking<br />exceeds a predefined level.<br />Background seismicity: small<br />tremors that occur constantly<br />during periods of quiescence<br />between major earthquakes.<br />
  11. 11. Seismogenic zones:-<br /><ul><li>the margins of tectonic plates</li></ul>(e.g. subduction zones)<br /><ul><li>zones of geological faults under stress
  12. 12. areas of volcanic activity</li></ul>and geothermal fluxes.<br />
  13. 13. Geological faults (extensive<br />planes that divide rock units):-<br /><ul><li>normal faults (extensional movement)
  14. 14. inverse (compressional movement)
  15. 15. transcurrent(lateral, strike-slip)
  16. 16. oblique(diagonal).</li></li></ul><li>Types of geological fault<br />Overthrust fault<br />Reverse fault<br />Right-lateral normal fault<br />(oblique slip)<br />Normal fault<br />Fault line<br />Hanging wall<br />Footwall<br />Dip<br />Right-lateral fault<br />(strike-slip)<br />
  17. 17. The elastic rebound theory<br />of H.F. Reid:<br /><ul><li>hypocentre (focus): small area in the</li></ul>crust where the earthquake begins<br /><ul><li>epicentre: the point on the surface</li></ul>directly above the hypocentre<br /><ul><li>deep focus earthquakes:</li></ul>hypocentre buried at least 80 km<br /><ul><li>shallow focus earthquakes:</li></ul>hypocentre <50 km, often <20 km.<br />
  18. 18. The elastic rebound theory of H.F. Reid<br />
  19. 19. Types of seismic wave:-<br />Body waves:<br />P, primus, compression or pressure <br />waves - longitudinal<br />S, secundus, shear waves - transverse<br />Surface waves:<br /> L, Love S, Stoneley<br /> R, Rayleigh C, channel<br />R waves travel at 92%of the speed of<br />S waves, which travel at 58%of the<br />speed of P waves, etc.....<br />
  20. 20. The main kinds of seismic wave<br />Primus<br />(pressure)<br />'P' waves<br />Body waves<br />Secundus<br />(shear)<br />'S' waves<br />Love<br />'L' waves<br />Surface waves<br />Rayleigh<br />'R' waves<br />
  22. 22. Instruments for measuring<br />seismic waves:-<br /><ul><li> seismometers produce</li></ul>a continuous trace<br /><ul><li>accelerometers only function</li></ul>when there is strong motion<br /> (which triggers them to record)<br />Seismic monitoring instruments,<br />synchronised to different wavelengths,<br />must have an optimum combination of<br />robustness and sensitivity.<br />
  23. 23. Seismometers<br />
  24. 24. Accelerometers<br />
  25. 25. Magnitude was originally defined as the<br />amplitude of the largest seismic wave<br />at a nominal 100 km from the epicentre<br /><ul><li>Richter scale: local magnitude, ML,</li></ul>no longer used because it is<br /> inaccurate at high magnitudes<br /><ul><li>various scales for S-waves
  26. 26. Moment Magnitude scale, MW,</li></ul>the world standard.<br />
  27. 27. In earthquakes energy expenditure<br />is proportional to magnitude:<br />the points on the magnitude scale have<br />a logarithmic relationship in terms<br />of energy release - thus:<br />M8= 31.6 x M7<br />
  28. 28. Relationship between magnitude<br />and other variables<br />
  29. 29. World seismic activity over<br />a typical eight-year period <br />Number of earthquakes<br />Magnitude<br />
  30. 30. Location of epicentres and<br />reconstruction of the macroseismic field:-<br /><ul><li>three seismic stations can</li></ul>locate an epicentre on the basis<br />of the radial distance computed<br />from the travel times of <br /> different kinds of wave<br /><ul><li>the isoseismsof the macroseismic</li></ul> field are based on the relationship<br /> between the tremors and damage.<br />
  31. 31. 5 minutes<br /> Time <br />S waves<br />with<br />different<br />frequences<br />Distance<br />1000 km<br />Epicentre<br />Slowing down of P and S waves<br />with distance from epicentre<br />
  32. 32. stn. 1<br />stn. 2<br />epicentre<br />stn. 3<br />Localisation of epicentre on the basis<br />of the arrival times of seismic waves<br />
  33. 33. Epicentres<br />and faults<br />located<br />for the<br />Bam, Iran,<br />earthquake<br />of 26 Dec.<br />2003.<br />
  34. 34. Effect of different geological materials<br />in amplifying seismic waves<br />
  35. 35. Extract from a seismic microzonation map<br />showing different shaking potentials<br />
  36. 36. A typical sequence of aftershocks <br />after a major seismic event<br />(Northridge, California, 1994)<br />Number of earthquake per day<br />all others m<5<br />Days after the earthquake<br />
  37. 37. Colfiorito earthquake swarm, central Italy<br />September - December 1997<br />Days after earthquake<br />Days after earthquake<br />Associated seismic intensities<br />Days after earthquake<br />
  38. 38. MCS intensities<br />for 23-11.1980<br />southern Italian<br />earthquake M6.8<br />
  39. 39. NEW ZEALAND <br />Intensities with a probability of<br />50% of returning within 50 years<br />Return periods of earthquakes<br />with intensities of at least MM=VI<br />
  40. 40. Comparative data on four earthquakes<br />
  41. 41. Consequences of<br />Earthquakes<br />- and significant issues -<br />
  42. 42. Construction failure poses the<br />greatest threat to life in<br />earthquakes<br />
  43. 43. Structural integrity:<br />a building's physical adequacy<br />for its intended purpose<br />Failure: total or partial<br />collapse, or the destruction or<br />non-functionality of a building.<br />
  44. 44. Seismic damage to buildings<br />is a function of:-<br /><ul><li> seismic energy expenditure:</li></ul>magnitude<br /> duration of strong motion<br /> maximum acceleration<br /><ul><li> distance from epicentre
  45. 45. surface geology</li></ul> (soft sediments amplify waves)<br /><ul><li> effect of construction type
  46. 46. regularity of building form
  47. 47. state of maintenance of building.</li></li></ul><li>
  48. 48.
  49. 49.
  50. 50. In the Tangshan (China) earthquake<br />of July 1976 (magnitude 7.6),<br />of 352 multi-storey buildings:<br /><ul><li>4 (1%) maintained their</li></ul> structural integrity<br /><ul><li>177(50%) collapsed completely
  51. 51. 85(24%) collapsed partially
  52. 52. 86(25%) were severely damaged.</li></li></ul><li>Knowledge must be gained of how to:-<br /><ul><li>buttress buildings temporarily
  53. 53. repair buildings permanently
  54. 54. design and construct</li></ul> buildings antiseismically.<br />
  55. 55.
  56. 56. Antiseismic design utilizes:-<br /><ul><li> experience of a building's</li></ul>seismic performance<br /><ul><li> hypotheses about a building's</li></ul> seismic response<br /><ul><li>design techniques to combat</li></ul> weaknesses in buildings<br /> induced by earthquakes.<br />
  57. 57. The largest urban seismic risk<br />is in Istanbul and Tehran<br />Major earthquakes represent an enormous<br />urban search-and-rescue (USAR) challenge<br />
  58. 58. The international relief system is<br />hugely expensive and inefficient<br />$1,000,000 per life saved!<br />
  59. 59. In Italy...<br /><ul><li>in the 20th century 46 lethal</li></ul> earthquakes caused 128,000 deaths<br /><ul><li>a damaging quake once in 24-56 months
  60. 60. greatest risk is in the</li></ul>22,000 historical town centres<br /><ul><li>70% of the population lives in</li></ul> municipalities classified seismic;<br />40% in 2,965 highly seismic ones<br /><ul><li>35.3% of homes in earthquake zones</li></ul> are anti-seismically constructed.<br />
  61. 61.
  62. 62.
  63. 63. DISASTER<br />VICTIM<br />Search and rescue<br />UNINJURED<br />INJURED<br />Medical assistance<br />Public health measures<br />IMPROVEMENT<br />OF CONDITION<br />WORSENING<br />OF CONDITION<br />HEALTHY<br />INFECTED<br />Medical aid<br />HEALTHY<br />IMPROVEMENT<br />OF CONDITION<br />WORSENING<br />OF CONDITION<br />Mortuarial<br />and funeral<br />services<br />DEATH<br /> DISEASES <br />INJURIES<br />
  64. 64. Injuries<br />Emergency room<br />injuries<br />Hospital<br />admissions<br />No damage<br />to buildings<br />Damage<br />to buildings<br />Source: Linda Bourque, UCLA<br />
  65. 65. In the Italian Irpinia-Basilicata<br />earthquake of 1980 hospitals collapsed.<br />In the El Salvador earthquake<br />of 1986 hospitals collapsed.<br />In the El Salvador earthquake<br />of 2001 hospitals collapsed.<br />In the Bam, Iran, earthquake<br />of 2003 hospitals collapsed.<br />....haven't we learnt anything at all?<br />
  66. 66. "At Olive View Medical Center, two buildings collapsed in 1971, and three people died, including two patients on life-support systems that failed when auxiliary generators did not start. The third was an ambulance driver who was crushed by a falling wall. Olive View was an 888-bed hospital then. It had only been open a month when the quake hit. Because of extensive damage, the hospital was rebuilt, with attention to strengthening it against any future quake. But it was much smaller. Now it has a capacity of 377 patients."<br />[Sylmar, California, history file]<br />
  67. 67. Of the 58 fatalities caused by building damage, 50 occurred in hospitals. The worst damage to medical facilities occurred at the Veterans Administration Hospital in Sylmar where two large buildings collapsed. Even though the hospital site was right on the edge of the heavily urbanized San Fernando Valley, it took one hour and 22 minutes before a fire department helicopter happened to spot the collapses and send help. The reason for such a delay? The phones didn’t work, the hospital’s radio was in one of the collapsed buildings, and the first message orally delivered by a hospital staff member to a nearby government facility was confused with an already received report of damage to a different nearby hospital.<br />[Reitherman 2004]<br />
  68. 68.
  69. 69.
  70. 70.
  71. 71.
  72. 72. Seismic hazards to hospitals:-<br /><ul><li> loss of structural integrity</li></ul> and building functionality<br /><ul><li> seismically-induced flooding,</li></ul>landsliding and subsidence<br /><ul><li> loss of trained personnel
  73. 73. loss of medical and surgical capacity
  74. 74. loss of supplies (including utilities)</li></ul> and failure of supply chains<br /><ul><li>inaccessibility.</li></li></ul><li>Hospitals<br />Seismic design level<br />Fully<br />operational<br />Operational<br />Life<br />safe<br />Near<br />collapse<br />Collapse<br />Unaccaptable<br />performance<br />Unaccaptable<br />performance<br />Rare<br />60%g<br />Unaccaptable<br />performance<br />Very<br />rare<br />80%g<br />
  75. 75. Capacity:<br /><ul><li> beds (expandable)
  76. 76. surgical and curative (fixed or</li></ul>diminished in the short term).<br />
  77. 77. Resilience<br /><ul><li> ensuring the structural integrity</li></ul> of the medical facility<br /><ul><li> ensuring continuity of</li></ul> services and medical supplies<br /><ul><li> ability to cope with very</li></ul> large surges in demand<br /><ul><li> protecting personnel and</li></ul> their immediate families<br /><ul><li> protecting lifelines that enable the</li></ul> injured to access medical care.<br />
  78. 78. Measures<br /><ul><li> seismic integrity surveys</li></ul> (structural and non-structural)<br /><ul><li> emergency planning (...testing,</li></ul> revising, diffusing plans...)<br /><ul><li> estimate medical, surgical,</li></ul> pharmaceutical and logistical needs<br /><ul><li> earthquake casualty estimation.</li></li></ul><li>Internal emergency plan<br />Site of the<br />disaster<br />Other<br />hospitals<br />and clinics<br />in the area<br />Health facility network<br />emergency plan<br />External<br />emergency plan<br />The three foci of medical emergency planning<br />
  79. 79. Disaster<br />planning for<br />the medical<br />centre<br />Disaster<br />planning<br />for the system<br />of medical<br />centres<br />Disaster<br />planning for<br />the external<br />environment<br />Disaster<br />in the medical<br />centre<br />Disaster<br />in the system<br />of medical<br />centres<br />Co-ordinated<br />EMS Disaster<br />plans<br />Disaster<br />in the external<br />environment<br />
  80. 80. Helicopter links<br />Ambulance routes<br />Emergency bus transportation<br />Telecommunications links<br />T1<br />T2<br />Primary triage point<br />Secondary triage points<br />Pulmonary<br />specialists<br />Hospital I<br />Hospital II<br />T2<br />Staging<br />area<br />T2<br />T1<br />Burns<br />unit<br />Disaster<br />T2<br />Secondary<br />treatment<br />centre<br />Incident<br />command<br />post<br />Incident<br />commander<br />Mortuary<br />Emergency<br />operations<br />commander<br />Emergency<br />operations<br />centre<br />Next-of-kin<br />Coroner<br />
  81. 81. IMPACT ON THE<br />COMMUNITY<br />RISK OF EARTHQUAKE <br />Characteristics<br />of the event:<br />magnitude,<br />duration,<br />location of<br />epicentre,<br />level ofground<br />acceleration<br />Buildings,<br />drinking water,<br />sewerage,<br />public transport,<br />public buildings,<br />hospitals,<br />fire stations,<br />etc.<br />Local geological<br />characteristics<br />Population<br />distribution<br />and density<br />Aftershocks<br />Socio-economic<br />characteristics<br />RISK OF EARTHQUAKE<br />Landslides<br />Previous<br />experience<br />of risk<br />Floods<br />Casualties,<br />economic damage;<br />type, costs times<br />of reconstruction<br />Fires<br />Level of<br />community<br />preparedness<br />
  82. 82. Thank<br />you<br />for<br />your<br />attention!<br />