My First Presentation

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

30. band-limited

31. the generated waves are time-varyingThe 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