Uploaded on

My First Presentation

My First Presentation

More in: Technology , Education
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Be the first to comment
    Be the first to like this
No Downloads

Views

Total Views
598
On Slideshare
0
From Embeds
0
Number of Embeds
0

Actions

Shares
Downloads
15
Comments
0
Likes
0

Embeds 0

No embeds

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
    No notes for slide

Transcript

  • 1. NAÏVE EFFORT OFA DAREDEVIL
    UTTERLY & TRULY A
    NOT-THAT-TECHNICAL
    PRESENTATION
    ON
    SEISMIC WAVES:
    Theory & Implications
    Propagation of seismic wave in the ground and the effect of presence of land mine.
    GEOSCIENCE CARESDEBA_PR11 GEOSCIENCE MATTERS
  • 2. PLEASE,DO GIVE IT A SHOT.
    GEOSCIENCE CARESDEBA_PR12 GEOSCIENCE MATTERS
  • 3. EXPERIENCING THE GEOSCIENCE FIELD EFFECT
    GEOSCIENCE FIELD EFFECT
    GEOSCIENCE CARESDEBA_PR13 GEOSCIENCE MATTERS
  • 4. GEOSCIENCE CARESDEBA_PR14GEOSCIENCE MATTERS
    GET SEISMIC!!!
  • 5. WHAT???
    Seismic waves are waves that travel through Earth, most often due to natural causes, sometimes from anthropogenic ones.
    ‘ TIS WAVE ?!
    “heavily overloaded
    with meanings”
    "stuff that wobbles
    in space and time“
    ( This is from a PF Mentor)
    P- and S-waves sharing with the propagation
    ATTENTION PLEASE!!!
    THERE IS
    TRANSFERANCE OF ENERGY!!!
    Waves can be represented by
    simple harmonic motion.
    GEOSCIENCE CARESDEBA_PR15GEOSCIENCE MATTERS
  • 6. ENERGY
    THE GREATEST MAKER!!!
    THE GREATEST BREAKER!!!
    In My Book,
    The Most Elusive Stuff
    In The Universe!
    ELECTROMAGNETIC SCATTERING Here two charged particles approach each other and scatter by exchanging a virtual photon. Animation reproduced by kind permission of (c) J. Eric Slone www.FeynmanOnline.com.
    (http://www.egglescliffe.org.uk/physics/particles/parts/parts1.html)
    Could you please define
    ENERGY?
    GEOSCIENCE CARESDEBA_PR16GEOSCIENCE MATTERS
  • 7. Elastic Wave Equation in Three Dimensions
    The elastic wave equation in three dimensions describes the propagation of waves in an isotropic homogeneous elastic medium. As most solid materials are elastic, seismic waves that travel through earth can be described by this equation:
    (2μ+λ) (   .ψ)–μ   ×(   ×ψ)=ρ(∂2ψ/∂t2) … … … (1)
    Where:
    λ and μ are the so-called Lamé parameters describing
    the elastic properties of the medium,
    ρ is density,
    ψ is the source function (driving force),
    This equation must account for both transverse and longitudinal motion. Here, both force and displacement are vector quantities. That’s why this equation is sometimes known as the vector wave equation.
    GEOSCIENCE CARESDEBA_PR17GEOSCIENCE MATTERS
  • 8. ‘TIS SEISMIC DELICACY!
    Seismic Waves come chiefly in
    TWO FLAVORS
    SO APPETIZING!!!!!
    GEOSCIENCE CARESDEBA_PR18GEOSCIENCE MATTERS
  • 9. BODY WAVES
    THIS STUFF ALSO COMES IN
    TWO FLAVORS.
    In an infinite homogeneous
    isotropic medium, only
    body waves exist.
    BODY WAVES
    GEOSCIENCE CARESDEBA_PR19GEOSCIENCE MATTERS
  • 10. P WAVE
    Putting ( ×ψ)=0 in the equation number 1
    we get P wave.
    This type of seismic wave is also
    variously known as a dilational,
    longitudinal, irrotational, compressional
    waves.
    It Involves alternatingly Compression
    and dilation.
    GEOSCIENCE CARESDEBA_PR110GEOSCIENCE MATTERS
  • 11. P WAVE
     Copyright 2004. L. Braile.
    GEOSCIENCE CARESDEBA_PR111GEOSCIENCE MATTERS
  • 12. S WAVE
    Putting ( .ψ)=0 in the equation
    number 1 we get S wave.
    This type of seismic wave is also
    variously known as a shear, transverse,
    rotational waves.
    It Involves Alternating transverse
    motion.
    GEOSCIENCE CARESDEBA_PR112GEOSCIENCE MATTERS
  • 13. S WAVE
    Transverse particle motion shown here is vertical but can be in any direction. However, Earth’s layers tend to cause mostly vertical (SV) or horizontal (SH) shear motions.
     Copyright 2004. L. Braile.
    GEOSCIENCE CARESDEBA_PR113GEOSCIENCE MATTERS
  • 14. VELOCITIES OF P AND S WAVES
    Velocities of P wave and S wave can be formulated as the following way:
    α={( λ+2μ)/ ρ}1/2
    β=(μ/ρ)½
    Where α and β stand for velocities of P wave and S wave respectively. As the elastic constants are positive, α is greater than β. Writing γ for the ratio β/ α we see that
    γ2= β2/α2= μ/( λ+2μ)= (1/2-σ)/(1-σ)
    As σ decreases from 0.5 to 0 γ increases from 0 to its maximum value 1/21/2.
    Therefore, the velocity of the S wave ranges from 0 to 70% of the velocity of the P wave.
    GEOSCIENCE CARESDEBA_PR114GEOSCIENCE MATTERS
  • 15. SHADOW ZONE
    S-waves do not pass through the earth's core, forming a Shadow Zone on the earth's side opposite from the epicenter. There is another shadow zone for P wave which is formed due to refraction.
    GEOSCIENCE CARESDEBA_PR115GEOSCIENCE MATTERS
  • 16. SURFACE WAVES
    Surface waves come in different flavors including Rayleigh, Love, Tube, Stoneley and Channel waves.
    We, however, confine ourselves to Rayleigh and Love waves for this presentation.
    When the medium does not
    extend to infinity in all
    directions, surface waves
    are produced.
    Surface Waves
    GEOSCIENCE CARESDEBA_PR116GEOSCIENCE MATTERS
  • 17. RAYLEIGH WAVE
    Propagates along the free surface of a semi-infinite medium.
    For a Poisson ratio of σ =1/4,the Rayleigh wave velocity is 0.9194 times the S wave Velocity.
    It can be thought of as special case of Stoneley wave( wave along a interface).
    GEOSCIENCE CARESDEBA_PR117GEOSCIENCE MATTERS
  • 18. RAYLEIGH WAVE
    Particle motion near the surface is elliptical and retrograde i.e., the particle moves opposite to the direction of propagation at the top of its elliptical path in the vertical plane containing the direction of propagation.
    Its amplitude decreases exponentially with depth, and the elastic properties to a depth of about one wavelength determine its velocity.
    GEOSCIENCE CARESDEBA_PR118GEOSCIENCE MATTERS
  • 19. FIG. R-3. Rayleigh-wave motion. (a) Theoretical Rayleigh wave has retrograde elliptical motion at the surface. (b) Hodograph of particle velocity involved in ground roll. (From Howell, 1959, 80.) (c) Experimental measurements from a small explosion measured with buried geophones showing the change from retrograde to prograde motion with depth. (After Dobrin, 1951).
    GEOSCIENCE CARESDEBA_PR119GEOSCIENCE MATTERS
  • 20. RAYLEIGH WAVE
    FIG. The dependence of Rayleigh wave velocity VR on Poisson’s ratio σ. The P-wave velocity is α and the S-wave velocity β.
    GEOSCIENCE CARESDEBA_PR120GEOSCIENCE MATTERS
  • 21. RAYLEIGH WAVE
     Copyright 2004. L. Braile.
    GEOSCIENCE CARESDEBA_PR121GEOSCIENCE MATTERS
  • 22. LOVE WAVE
    This is a seismic channel wave associated with
    a surface layer that has rigidity, characterized
    by horizontal motion perpendicular to the
    direction of propagation with no vertical
    motion. It may be thought of as channel waves
    in the upper layer.
    Earthquake love waves have velocities up to
    4.5 km/s, faster than Rayleigh waves.
    GEOSCIENCE CARESDEBA_PR122GEOSCIENCE MATTERS
  • 23. LOVE WAVE
    It can travel by different modes,
    designated by the number of nodal
    planes within the layer. However,
    usually only the zero mode is observed.
    The dispersion of love waves can be
    used to calculate the thickness of the
    surface layer.
    GEOSCIENCE CARESDEBA_PR123GEOSCIENCE MATTERS
  • 24. LOVE WAVE
    FIG. Earthquake seismogram schematic (a) The vertical component; (b) one horizontal component
    GEOSCIENCE CARESDEBA_PR124GEOSCIENCE MATTERS
  • 25. LOVE WAVE
     Copyright 2004. L. Braile.
    GEOSCIENCE CARESDEBA_PR125GEOSCIENCE MATTERS
  • 26. John Lahr demonstrates seismic waves on slinkies.
    URL:www.exo.net/.../summer_day10waves/wavetypes.html
    GEOSCIENCE CARESDEBA_PR126GEOSCIENCE MATTERS
  • 27. HOW???
    SEISMIC SOURCE
    A Seismic Source generates seismic energy.
    Then Where do they come from?
    Sorry! Sorry! Sorry!
    It’s not from
    Heaven or Hell!
    They have
    Mundane Sources.
    AGAIN TWO
    FLAVORS!!!
    GEOSCIENCE CARESDEBA_PR127GEOSCIENCE MATTERS
  • 28. NATURAL SEISMIC SOURCES
    Natural seismic sources include the following ones:
    EARTHQUAKES
    VOLCANOES
    INFRASOUND FROM
    THUNDERSTORM
    Sh!
    Mom
    Is
    Furious
    !!!!
    Thunder is the sound made by the lightning
    GEOSCIENCE CARESDEBA_PR128GEOSCIENCE MATTERS
  • 29. ARTIFICIAL SEISMIC SOURCES
    An artificial seismic source generates controlled seismic energy that is used in both reflection and refraction seismic surveys.
    A seismic source signal has the following characteristics:
    • generated as an impulsive source
    • 30. band-limited
    • 31. the generated waves are time-varying
    The generalized equation that shows all above
    properties
    where fmax is the maximum frequency component of the generated waveform.
    GEOSCIENCE CARESDEBA_PR129GEOSCIENCE MATTERS
  • 32. ARTIFICIAL SEISMIC SOURCES
    The Artificial
    Seismic Sources:
    EXPLOSIVES
    AIR GUN
    PLASMA SOUND
    SOURCE
    THUMPER TRUCK
    VIBROSEIS SOURCES
    BOOMER SOURCES
    Hey
    Kids!
    No
    More
    Pranks
    !!!
    An air gun seismic source (30 litre).
    Plasma sound source fired in small swimming pool.
    GEOSCIENCE CARESDEBA_PR130GEOSCIENCE MATTERS
  • 33. WHY??????
    THEN,
    WHY SHOULD WE BOTHER
    TO TEASE
    OUR EXTRAORDINARY BRAINS
    STUDYING
    ALL THESE STUFFS!?!?!?!?!?
    GEOSCIENCE CARESDEBA_PR131GEOSCIENCE MATTERS
  • 34. ‘CAUSE WE KNOW THAT’S NOT A WASTE.
    This is worth investing
    our money, time and effort.
    HERE, WE WILL FOCUS ON THE FOLLOWING ONES
    TO HAVE AN IDEA.
    First: SURVIVING THE HARSHNESS
    OF MOTHER NATURE
    Second: WHY DO INDUSTRIES CARE?
    GEOSCIENCE CARESDEBA_PR132GEOSCIENCE MATTERS
  • 35. SURVIVING THE HARSHNESS OF MOTHER NATURE
    To Fight the EARTHQUAKES a complete grasp of SEISMIC WAVE is INDISPENSABLE.
    IF YOU CARE
    THE SHAKE,
    YOU HAVE GOT TO CARE ABOUT IT.
    OTHERWISE
    YOU NEED NOT!!!!!!!!!!
    GEOSCIENCE CARESDEBA_PR133GEOSCIENCE MATTERS
  • 36. SURVIVING THE HARSHNESS OF MOTHER NATURE
    TSUNAMIS
    AND
    EARTHQUAKES
    SHARE
    A COMMON ORIGIN.
    THEREFORE,
    TO SURVIVE
    TSUNAMIS
    SEISMIC WAVES
    HAVE GOT TO
    SURVIVE.
    GEOSCIENCE CARESDEBA_PR134GEOSCIENCE MATTERS
  • 37. SURVIVING THE HARSHNESS OF MOTHER NATURE
    AT TIMES,
    STUDYING
    SEISMIC
    WAVES
    WE CAN
    PREDICT
    VOLCANIC
    ERRUPTION.
    THEREFORE, GET SEISMIC
    AND HE COULD NO LONGER SAY:
    I LAVA YOU!
    GEOSCIENCE CARESDEBA_PR135GEOSCIENCE MATTERS
  • 38. WHY DOES INDUSTRY CARE?
    SEISMIC METHOD IS VIRTUALLY ALL SEISMIC WAVE.
    I KNOW
    YOU MUST KNOW THAT!!!
    AND
    WHEN PEOPLE MEAN
    HYDROCARBON INDUSTRIES,
    WE --GEOSCIENCE FOLKS --
    MEAN
    SEISMIC METHODS.
    GEOSCIENCE CARESDEBA_PR136GEOSCIENCE MATTERS
  • 39. WHY DOES INDUSTRY CARE?
    The SEISMIC METHODS are by far the most
    important geophysical techniques in terms of
    expenditures and number of geophysicists
    involved.
    GEOSCIENCE CARESDEBA_PR137GEOSCIENCE MATTERS
  • 40. WHY DOES INDUSTRY CARE?
    G: gravity; M: magnetic; S: seismic; E: electrical; SP: self
    potential; IP: induced polarization; EM: electromagnetic; Subsidiary methods in parentheses.
    GEOSCIENCE CARESDEBA_PR138GEOSCIENCE MATTERS
  • 41. WHY DOES INDUSTRY CARE?
    SEISMIC REFLECTION SURVEYING
    In Seismic Reflection Surveys the travel times are
    measured of arrivals reflected surface interfaces between
    media of different acoustic impedance.
    Reflection surveys are most commonly carried out in
    areas of shallowly dipping sedimentary sequences.
    In such situations, velocity varies much more as a
    function of depth, due to lateral facies changes within the
    individual Layers. For the purposes of initial
    considerations, the horizontal variations of velocities may
    be ignored.
    GEOSCIENCE CARESDEBA_PR139GEOSCIENCE MATTERS
  • 42. WHY DOES INDUSTRY CARE?
    SEISMIC REFRACTION SURVEYING
    The seismic refraction survey method utilizes seismic
    energy that returns to surface after traveling through the
    ground along refracted ray paths.
    The method is normally used to locate refracting
    interfaces (refractors) separating layers of different
    seismic velocity, but the method is also applicable in
    cases where velocity varies smoothly as a function of
    depth or laterally.
    GEOSCIENCE CARESDEBA_PR140GEOSCIENCE MATTERS
  • 43. WHY DOES INDUSTRY CARE?
    Refraction seismology is applied to a very wide range
    of scientific and technical problems, from engineering
    site investigation surveys to large scale experiments
    designed to study the structure of the entire crust or
    lithosphere.
    Refraction measurements can provide valuable velocity
    information for use in the interpretation of reflection
    surveys, and refracted arrivals recorded during land
    reflection surveys are used to map the weathered layer.
    This wide variety of applications leads to wide variety
    of field survey methods and associated interpretation
    techniques.
    GEOSCIENCE CARESDEBA_PR141GEOSCIENCE MATTERS
  • 44. REFERENCES
    W.M. Telford et al., APPLIED GEOPHYSICS, 2nd Edition
    P. KEAREY et al., AN INTRODUCTION TO GEOPHYSICAL EXPLORATION
    http://en.wikipedia.org/
    http://www.psc.edu/science/2006/inprogress/images/quake_fig2.jpg
    http://www.mysupplychain.co.uk/images/mainpic4_uncertainty.jpg
    http://www.teachingboxes.org/earthquakes/lessons/rev-Squiggles_clip_image001.gif
    http://web.ics.purdue.edu/~braile/edumod/waves/WaveDemo.htm
    www.matter.org.uk/.../shadow_zone.html
    http://iri.columbia.edu/~lareef/tsunami/
    http://segdl.org/dictionary/
    AND
    Other sources which cannot be enumerated here.
    GEOSCIENCE CARESDEBA_PR142GEOSCIENCE MATTERS
  • 45. PRESENTER
    F
    R
    E
    S
    H
    M
    A
    N
    THE DAREDEVIL
    DEBAJYOTI
    BASU SARKAR
    JN 024
    DEPT. OF GEOLOGY
    UNIVERSITY OF DHAKA
    GEOSCIENCE CARESDEBA_PR143GEOSCIENCE MATTERS
  • 46. LOTS AND
    LOTS AND
    LOTS OF
    FOR
    YOUR TIME &
    EFFORT!!!!!!!!
    THANKS
    GEOSCIENCE CARESDEBA_PR144GEOSCIENCE MATTERS