Earthquakes And Evs

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Earthquakes And Evs

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Earthquakes And Evs

  1. 1. EARTHQUAKES : CAUSES AND PREDICTIONS   by   Prof. R. N. Tiwari Department of Geology Banaras Hindu University
  2. 2. Natural Hazard <ul><li>Worst natural hazard </li></ul><ul><li>Impact over a large area </li></ul><ul><li>Causing destruction on massive scale </li></ul><ul><li>Loss of human life and property </li></ul><ul><li>Devastation is quick and sudden </li></ul><ul><li>No time to escape </li></ul>
  3. 3. Major Earthquakes <ul><li>China- 1177 </li></ul><ul><li>Peru- 1471 </li></ul><ul><li>Lisbon – 1755 </li></ul><ul><li>California- 1906 </li></ul><ul><li>Tokyo- 1923 </li></ul><ul><li>Chili- 1960 </li></ul><ul><li>Last two decades – (1982-2000) 26 major earthquakes- casualities-150000 </li></ul>
  4. 5. <ul><li>Occurrence of earthquakes- frequent </li></ul><ul><li>No body can remain without being affected </li></ul><ul><li>Every time people get panic </li></ul><ul><li>Series of questions arise </li></ul>
  5. 7. Definition <ul><li>An earthquake is vibration of earth produced by rapid release of energy </li></ul><ul><li>Energy released radiates in all directions from its source </li></ul><ul><li>Energy is in the form of waves </li></ul><ul><li>Sensitive instruments around the world record the event </li></ul>
  6. 8. Seismic Waves <ul><li>Longitudinal (P) Waves </li></ul><ul><li>Highest velocity, 5-7 km./ sec. </li></ul><ul><li>Can travel solid and liquid both </li></ul><ul><li>Transverse (S) Waves </li></ul><ul><li>Lower velocity-3-5Km./Sec. </li></ul><ul><li>Do not pass in liquid and gases </li></ul><ul><li>Surface (L) Waves </li></ul><ul><li>Travel along outer part of earth with great amplitude and slowest velocity </li></ul><ul><li>Cause greatest destruction </li></ul>
  7. 10. Focus and Epicentre <ul><li>Focus : The place in the earth crust where the earth shocks occur </li></ul><ul><li>Epicenter : The point at the surface immediately above the focus. </li></ul>
  8. 11. Location of Epicenter <ul><li>The time intervals between the first arrivals of P and S waves are used to determine the distance between a seismograph and the earthquake epicenter </li></ul><ul><li>Three or more stations are needed to determine the location of an earthquake . </li></ul>
  9. 13. Seismograph: Instrument to design to register earthquake waves Seismogram : Recording of earthquake waves on a paper
  10. 14. Seismograph
  11. 15. Magnitude And Intensity Of Earthquakes <ul><li>The severity of an earthquake can be expressed in several ways. </li></ul><ul><li>Magnitude and Intensity measure different characteristics of earthquakes. </li></ul><ul><li>Intensity measures the strength of shaking produced by the earthquake at a certain location. It is determined from effects on people, human structures, and the natural environment . </li></ul><ul><li>Magnitude measures the energy released at the source of the earthquake. It is determined from measurements on seismographs and usually expressed by the Richter Scale </li></ul>
  12. 17. Richter Scale <ul><li>< 2 Generally not felt but recorded </li></ul><ul><li>2.0 – 2.9 Potentially perceptible </li></ul><ul><li>3.0 – 3.9 Felt by some </li></ul><ul><li>4.0 – 4.9 Felt by most </li></ul><ul><li>5.0 – 5.9 Damaging shocks </li></ul><ul><li>6.0 – 6.9 Destructive in populated regions </li></ul><ul><li>7.0 – 7.9 Major Earthquakes; Inflict serious damages </li></ul><ul><li>>8 Great Earthquakes; cause extensive </li></ul><ul><li>destruction near epicenter </li></ul><ul><li>( Maximum known 8.9 ) </li></ul>
  13. 18. Magnitude / Intensity Comparison Magnitude Typical Maximum Modified Mercalli Intensity 1.0 - 3.0 I 3.0 - 3.9 II - III 4.0 - 4.9 IV - V 5.0 - 5.9 VI - VII 6.0 - 6.9 VII - IX 7.0 and higher VIII or higher
  14. 19. Effects of Earthquakes <ul><li>  </li></ul><ul><li>1.    Loss of human life and property </li></ul><ul><li>2.    Displacement of roads, rails, canals, </li></ul><ul><li>bridges, dams, etc. </li></ul><ul><li>3.    Landslides, formation of lake, change of </li></ul><ul><li>stream channel </li></ul><ul><li>4.    Liquefaction where ground is very wet with </li></ul><ul><li>higher water table, common in coastal </li></ul><ul><li>areas </li></ul><ul><li>5.Tsunamis occur following violent movement of </li></ul><ul><li>the sea floor generated by seismic sea waves. </li></ul>
  15. 24. Liquefaction
  16. 27. Liquefaction in Japan
  17. 28. Tsunami <ul><li>Underwater earthquakes </li></ul><ul><li>Seismic waves moving large bodies of water </li></ul><ul><li>Result from vertical displacement along a fault located on ocean floor </li></ul>
  18. 29. Tsunami Waves <ul><li>Deep water </li></ul><ul><li>• In the deep ocean the waves may go by unnoticed (low wave height) </li></ul><ul><li>• Wave speed 800 km/hr </li></ul><ul><ul><li>Shallow water – Height exceeds 30m. </li></ul></ul><ul><ul><li>Very destructive </li></ul></ul>
  19. 30. Tsunami
  20. 32. Warning System
  21. 34. Earth’s History <ul><li>Earth - one of the nine planets of solar system </li></ul><ul><li>Originated about 4500-4600 M.Y. </li></ul><ul><li>Today continents are separated by ocean </li></ul><ul><li>About 250 my. There was one continent and one ocean called Pangaea and Panthalasa </li></ul><ul><li>About 200my. Pangaea split into two major continents- Laurasia and Gondwana land </li></ul><ul><li>Indian plate travelled 9 m per century </li></ul><ul><li>Collided with Eurasia plate- 40-50my. </li></ul><ul><li>Formation of Himalaya </li></ul>
  22. 36. Earth Structure <ul><li>Seismic waves revealed – earth has radially layered structure </li></ul><ul><li>Three main divisions- Crust, Mantle and Core </li></ul><ul><li>Each layer has distinctive physical chemical and seismic characters </li></ul>
  23. 37. Mechanical division of Earth <ul><li>Lithosphere - </li></ul><ul><li>100-150 km. below Continent </li></ul><ul><li>70-100 Km. below Ocean </li></ul><ul><li>More rigid – forming hard outer shell </li></ul><ul><li>Divided in to several large fragments- called Plates </li></ul><ul><li>Asthenosphere- </li></ul><ul><li>150 Km. thick, lies beneath lithosphere </li></ul><ul><li>Lower rigidity partly molten </li></ul>
  24. 39. Tectonic Plates <ul><li>Twelve major plates </li></ul><ul><li>Antarctica, Africa, Eurasia, India, Australia, Arabia, Philippines, North America, South America, Pacific, Nazca and Cocos </li></ul><ul><li>Earthquake occurs on plate margins </li></ul><ul><li>Associated with interaction between plates </li></ul>
  25. 42. Types of Plate Margin <ul><li>Constructive (divergent) plate margin </li></ul><ul><li>Spreading centre, plate moving a part </li></ul><ul><li>Destructive (convergent) plate margin </li></ul><ul><li>Subduction zone, One plate forced under another, Plates bent sharply </li></ul><ul><li>Conservative plate margin: </li></ul><ul><li>Formed by transform fault </li></ul><ul><li>Lithosphere is neither created nor destroy </li></ul><ul><li>Convection current generated in the mantle moves the plates </li></ul>
  26. 46. Cause of Earthquakes <ul><li>Brittle condition of the lithosphere causes fracture when strongly stressed </li></ul><ul><li>Rupture produces an earthquakes </li></ul><ul><li>A violent release of elastic energy due to sudden displacement on a fault plane </li></ul>
  27. 47. Cause of Earthquakes • Moving Plates • Release of energy from within the Earth
  28. 48. Earthquakes and Fault <ul><li>Movements that produced earthquakes are usually associated with large fractures in earth’s crust called faults </li></ul><ul><li>Motion along faults can be explained by plate tectonic theory </li></ul>
  29. 49. Fault: A fracture or system of fractures along which rocks have been displaced.
  30. 50. Types of Fault <ul><li>Normal </li></ul><ul><li>Reverse </li></ul><ul><li>Strike slip </li></ul><ul><li>Right lateral, </li></ul><ul><li>Left lateral </li></ul>
  31. 57. Elastic Rebound <ul><li>Mechanism for earth quakes was explained by H.F. Reid </li></ul><ul><li>Rocks on both side of an existing fault are deformed by tectonic forces </li></ul><ul><li>Rocks bend and store elastic energy </li></ul><ul><li>Frictional resistance holding the rocks together is overcome </li></ul>
  32. 58. Earthquake Mechanism <ul><li>Slippage at the weakest point (focus) occur </li></ul><ul><li>Vibrations (earthquakes) occur at the deformed rock “ springs back” to its original shape (elastic rebound) </li></ul>
  33. 60. Earthquakes Distribution <ul><li>Earthquakes are generally distributed in belts . Eighty percent of the world's earthquakes occur in the circum-Pacific belt. Earthquakes also occur on the Mediterranean-Himalayan belt, and along other plate boundaries. </li></ul>
  34. 65. Earthquake mitigation <ul><li>Government </li></ul><ul><li>Science/Technology </li></ul><ul><li>Personal responsibility </li></ul>
  35. 66. Government <ul><li>Laws </li></ul><ul><li>• Developing in seismically active areas? </li></ul><ul><li>• Building codes </li></ul><ul><li>• Emergency response </li></ul>
  36. 67. Technology <ul><li>Earthquake prediction </li></ul><ul><li>Base isolation designs </li></ul>
  37. 68. Prediction <ul><li>• Natural </li></ul><ul><li>• Scientific </li></ul><ul><li>• The natural world is unpredictable! </li></ul>
  38. 69. <ul><li>Natural </li></ul><ul><ul><li>Animal behavior – Dogs barking excessively </li></ul></ul><ul><ul><li>– Pigs not eating climbing walls </li></ul></ul><ul><ul><li>– Cats left buildings </li></ul></ul><ul><ul><li>– Rats/mice left hidings places </li></ul></ul><ul><li>Scientific </li></ul><ul><li>Seismic monitoring </li></ul><ul><li>Elevation changes in land surface </li></ul><ul><li>Groundwater level changes </li></ul>
  39. 70. Earthquake prediction <ul><li>Earthquake prediction may be possible by </li></ul><ul><li>Measuring ground tilt, </li></ul><ul><li>Fault movement, </li></ul><ul><li>Seismic activity, </li></ul><ul><li>Changes in the earth’s magnetic field </li></ul><ul><li>Presence of radon gas in wells. </li></ul>
  40. 71. <ul><li>No reliable method exist for making short range earthquake prediction </li></ul><ul><li>Long term predictions based on occurrence of earthquakes on a time scale-30-100 years or more. </li></ul><ul><li>Using historical record on paleoseismology </li></ul>
  41. 72. Disaster Management Programme <ul><li>Cultivate a culture of disaster preparedness. </li></ul><ul><li>Think about disaster management as a regular, day to day thing </li></ul><ul><li>Disaster planning should begin at home </li></ul><ul><li>School children should be taught basic safety measures </li></ul><ul><li>Radio, TV., can be used to explain these things </li></ul><ul><li>Designs of building should be earthquake safe and must be approved by competent authority. </li></ul><ul><li>Identify bad building and get them repaired. </li></ul>
  42. 73. Preventive measures against building collapse <ul><li>Houses should have a uniform square or a rectangular plan </li></ul><ul><li>The L/B ratio should be from 0.15 to 0.20 </li></ul><ul><li>Foundation / plinth should be at least 1.5 times thicker than the wall </li></ul><ul><li>Doors and windows should be placed at corners of the room, 24 inches away from the room edges, minimum gap of 60cm. Between doors and windows </li></ul><ul><li>Mortar ratio – Cement: sand = 1:6 </li></ul><ul><li>- Cement: lime: sand = 1:2:9 </li></ul>
  43. 74. <ul><li>R.C.C. bands should be used at chair, door and roof levels </li></ul><ul><li>Window porches and roofs should protrude minimal </li></ul><ul><li>Jambs should be placed at corners between walls to provide strength and elasticity </li></ul><ul><li>Iron rods should be vertically placed in corners </li></ul><ul><li>Houses build of stone- wall should not be thicker than 45 cm. and R.C.C bands should used at each stage. </li></ul><ul><li>Above all, the material used should be of good quality----after all it is your sweet home </li></ul>
  44. 75. Thank You

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