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Overview ta3520 Introduction to seismics <ul><li>Fourier Analysis </li></ul><ul><li>Basic principles of the Seismic Method...
Signal and Noise Signal: desired Noise: not desired So for reflection seismology: - Primary reflections are signal - Every...
Signal and Noise (2) Direct wave: noise Refraction: noise Reflection: (desired) signal
Signal and Noise (3) Direct wave: noise Refraction: noise Reflection: signal Multiply reflected : noise
Signal and Noise for P-wave survey <ul><li>Noise: </li></ul><ul><li>direct wave through first layer </li></ul><ul><li>dire...
Signal and Noise for P-wave survey Goal of Processing: Remove effects of All-but-Primary-Reflection Energy Signal Noise = ...
Processing of Signal  (Primary-reflected energy) Goal of processing: Focus energy to where it comes from
Understanding signal and noise: wave theory Basic physics underlying signal is captured by  wave equation Ray theory: appr...
The seismic record
Body waves: Surface waves:
A seismic shot record on land Linear event: Direct/refraction Linear event: Slower, Direct Slightly hyperbolic event: Refl...
A seismic shot record on land Linear event: Direct/refraction Linear event: Slower, Direct Slightly hyperbolic event: Refl...
Interpretation of seismic land record thickness 200 m source detector offset air wave surface wave (velocity 1850 m/s) ref...
(Old: Interpretation of seismic land record)
Picture made within PowerPoint thickness 200 m source detector offset air wave surface wave (velocity 1850 m/s) refraction...
Modelling of seismic land record Observed data Modelled data (ray theory approx.)
Modelling of seismic land record Observed data Modelled data (ray theory approx.) refraction direct P-wave surface wave re...
Wassenaar-beach data: Wednesday
Wassenaar-beach data: Wednesday
Wassenaar-beach data:  array data (Thursday)
A seismic shot record at Wassenaar beach Linear event: Direct/refraction Linear event: Slower, Direct Many slightly hyperb...
Interpretation of Wassenaar  record
Modelling of Wassenaar record Observed data Modelled data (ray theory approx.)
A seismic shot record at sea Many Hyperbolic events: Reflections Linear event: Direct First hyperbolic event: primary refl...
Interpretation of marine record 300 m source detector offset direct P wave refraction velocity 240 m/s velocity 1500 m/s (...
Picture made with PowerPoint 300 m source detector offset direct P wave refraction velocity 240 m/s velocity 1500 m/s (P w...
Old: Modelling of marine record Observed data Modelled data (ray theory approx.)
Modelling of marine record Observed data Modelled data (ray theory approx.) refraction direct P-wave (water) reflections m...
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Presentation Chapter 4: Interpretation of Raw Seismic Records

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Transcript of "Presentation Chapter 4: Interpretation of Raw Seismic Records"

  1. 1. Overview ta3520 Introduction to seismics <ul><li>Fourier Analysis </li></ul><ul><li>Basic principles of the Seismic Method </li></ul><ul><li>Interpretation of Raw Seismic Records </li></ul><ul><li>Seismic Instrumentation </li></ul><ul><li>Processing of Seismic Reflection Data </li></ul><ul><li>Vertical Seismic Profiles </li></ul><ul><li>Practical: </li></ul><ul><li>Processing practical (with MATLAB) </li></ul>
  2. 2. Signal and Noise Signal: desired Noise: not desired So for reflection seismology: - Primary reflections are signal - Everything else is noise!
  3. 3. Signal and Noise (2) Direct wave: noise Refraction: noise Reflection: (desired) signal
  4. 4. Signal and Noise (3) Direct wave: noise Refraction: noise Reflection: signal Multiply reflected : noise
  5. 5. Signal and Noise for P-wave survey <ul><li>Noise: </li></ul><ul><li>direct wave through first layer </li></ul><ul><li>direct air wave </li></ul><ul><li>direct surface wave </li></ul><ul><li>S-wave </li></ul><ul><li>Multiply reflected wave </li></ul><ul><li>Refraction / Head wave </li></ul><ul><li>Desired signal: </li></ul><ul><li>primary reflected P-waves </li></ul>
  6. 6. Signal and Noise for P-wave survey Goal of Processing: Remove effects of All-but-Primary-Reflection Energy Signal Noise = Primary P-wave Reflected Energy All but Primary Reflection Energy
  7. 7. Processing of Signal (Primary-reflected energy) Goal of processing: Focus energy to where it comes from
  8. 8. Understanding signal and noise: wave theory Basic physics underlying signal is captured by wave equation Ray theory: approximation of wave equation (“high-frequency”) Resonances: modes expansion of wave equation S-waves, P-waves: elastic form of wave equation
  9. 9. The seismic record
  10. 10. Body waves: Surface waves:
  11. 11. A seismic shot record on land Linear event: Direct/refraction Linear event: Slower, Direct Slightly hyperbolic event: Reflection Linear event: Very slow, Direct
  12. 12. A seismic shot record on land Linear event: Direct/refraction Linear event: Slower, Direct Slightly hyperbolic event: Reflection Linear event: Very slow, Direct
  13. 13. Interpretation of seismic land record thickness 200 m source detector offset air wave surface wave (velocity 1850 m/s) refraction velocity 340 m/s velocity 3500 m/s (P waves) velocity 4800 m/s
  14. 14. (Old: Interpretation of seismic land record)
  15. 15. Picture made within PowerPoint thickness 200 m source detector offset air wave surface wave (velocity 1850 m/s) refraction velocity 340 m/s velocity 3500 m/s (P waves) velocity 4800 m/s
  16. 16. Modelling of seismic land record Observed data Modelled data (ray theory approx.)
  17. 17. Modelling of seismic land record Observed data Modelled data (ray theory approx.) refraction direct P-wave surface wave reflection reflection direct air wave
  18. 18. Wassenaar-beach data: Wednesday
  19. 19. Wassenaar-beach data: Wednesday
  20. 20. Wassenaar-beach data: array data (Thursday)
  21. 21. A seismic shot record at Wassenaar beach Linear event: Direct/refraction Linear event: Slower, Direct Many slightly hyperbolic events: Reflections ! Linear event: Slow, Direct
  22. 22. Interpretation of Wassenaar record
  23. 23. Modelling of Wassenaar record Observed data Modelled data (ray theory approx.)
  24. 24. A seismic shot record at sea Many Hyperbolic events: Reflections Linear event: Direct First hyperbolic event: primary reflection Hyperbolic event at twice time of primary reflection: multiple Linear event: Refraction
  25. 25. Interpretation of marine record 300 m source detector offset direct P wave refraction velocity 240 m/s velocity 1500 m/s (P waves) velocity 1500 m/s (density different) 250 m reflection multiple reflection
  26. 26. Picture made with PowerPoint 300 m source detector offset direct P wave refraction velocity 240 m/s velocity 1500 m/s (P waves) velocity 1500 m/s (density different) 250 m reflection multiple reflection
  27. 27. Old: Modelling of marine record Observed data Modelled data (ray theory approx.)
  28. 28. Modelling of marine record Observed data Modelled data (ray theory approx.) refraction direct P-wave (water) reflections multiple reflection multiple reflection
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