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Earthquakes And Evs
 

Earthquakes And Evs

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Earthquakes And Evs

Earthquakes And Evs

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    Earthquakes And Evs Earthquakes And Evs Presentation Transcript

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