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IMAGING & INTERPRETING CONTINENTAL LOWER CRUST: FROM POTENTIAL PROBLEMS TO PROBABLE PROCESSES

IMAGING & INTERPRETING CONTINENTAL LOWER CRUST: FROM POTENTIAL PROBLEMS TO PROBABLE PROCESSES. Kabir Roy-Chowdhury Utrecht University, The Netherlands. Imaging & Interpreting CLC Deterministic Probabilistic. Fellow Travellers Quarry Blasters at Univ Hamburg: Menzel

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IMAGING & INTERPRETING CONTINENTAL LOWER CRUST: FROM POTENTIAL PROBLEMS TO PROBABLE PROCESSES

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  1. IMAGING & INTERPRETINGCONTINENTAL LOWER CRUST:FROM POTENTIAL PROBLEMS TO PROBABLE PROCESSES Kabir Roy-Chowdhury Utrecht University, The Netherlands DSX-08 Saariselka June 8-13, 2008

  2. Imaging & Interpreting CLC Deterministic Probabilistic • Fellow Travellers • Quarry Blasters at Univ Hamburg: Menzel • The Instt. Of Geophysics, Kiev • The DSS group at N.G.R.I. Hyderabad • Geo-Sciences, Princeton: Phinney, Kong, Hansen • Geo-Sciences, Utrecht: Douma, Carpentier • Levander, Hurich, Holliger and many others … • And also Geologists like Smithson, Rutter, … KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008

  3. Imaging & Interpreting CLC Deterministic Probabilistic • Late ’60s – early ’70s • Recording quarry blasts with MARS recorders • Sporadic locations with 3 channels @ 500 m • Phase correlations of refracted arrivals • Modelling (scattered) wave-forms from MOHO • Transition zone? Linear gradient? Lamellae? KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008

  4. Imaging & Interpreting CLC Deterministic Probabilistic • Indo – Soviet collaboration (1972 -) • Kiev group had contoured Moho below Ukraine! • 660 km Kavali – Udipi profile in Indian Shield • 50-1500 Kg source, 100 m spacing, analogue rec • Human-intensive processing … KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008

  5. Imaging & Interpreting CLC Deterministic Probabilistic Processing DSS records KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008

  6. Imaging & Interpreting CLC Deterministic Probabilistic • Indo – Soviet collaboration (1972 -) • Kiev group had contoured Moho below Ukraine! • 660 km Kavali – Udipi profile in Indian Shield • 50-1500 Kg source, 100 m spacing, analogue rec • Human-intensive processing • Reciprocal (Deep) Reflection Segments Helped • First Danger Signals for Interpretation • Vertical vs.Horizontal Tectonics … KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008

  7. Imaging & Interpreting CLC Deterministic Probabilistic Gibbs, 1986 KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008

  8. Imaging & Interpreting CLC Deterministic Probabilistic • 1980s: CERP at Princeton • Try to Objectivise the Ubiquitous Line-Drawing • Coherency Filter (Kong et al, 1985) … KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008

  9. Imaging & Interpreting CLC Deterministic Probabilistic Kong et al, 1985 KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008

  10. Imaging & Interpreting CLC Deterministic Probabilistic • 1980s: CERP at Princeton • Objectivise the Ubiquitous Line-Drawing • Coherency Filter (Kong et al, 1985) … • The USGS Long-Island line as a benchmark … KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008

  11. Imaging & Interpreting CLC Deterministic Probabilistic Phinney & Roy-Chowdhury, 1989 KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008

  12. Imaging & Interpreting CLC Deterministic Probabilistic COCORP Georgia Lines 1 (above) and 5 (below) Phinney & Roy-Chowdhury, 1989 KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008

  13. Imaging & Interpreting CLC Deterministic Probabilistic • 1980s: CERP at Princeton • Objectivise the Ubiquitous Line-Drawing • Coherency Filter (Kong et al, 1985) … • The USGS Long-Island line as a benchmark … • Sign Filter (Hansen et al, 1988) … KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008

  14. Imaging & Interpreting CLC Deterministic Probabilistic Hansen et al, 1988 KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008

  15. Imaging & Interpreting CLC Deterministic Probabilistic • 1980s: CERP at Princeton • Objectivise the Ubiquitous Line-Drawing • Coherency Filter (Kong et al, 1985) … • The USGS Long-Island line as a benchmark … • Sign Filter (Hansen et al, 1988) … • Second Danger Signal for interpretation • Look beyond Phase … to Amplitudes too • Black/White problem (Seismix88 in Canberra) KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008

  16. Imaging & Interpreting CLC Deterministic Probabilistic • Enigma of Lower Crustal Reflectivity • Exposures exhibit multi-scale structure • Compositional and Evolutionary causes • Banded reflectivity at mid/lower- crustal depths • Compute Response of a Random Bi-modal Stack • Vertical Reflection Coefficient could be ~ 0.7! • Classify Regions based upon Back-Scattering Roy-Chowdhury et al, 1988 KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008

  17. Imaging & Interpreting CLC Deterministic Probabilistic • 1990s: let’s go stochastic • An explosion of people and papers • Random Layering gives Banded Reflectivity • Crustal Exposures show von Karman structure • Difficult to estimate the relevant parameters • Quantitative? Interpretation of Deep Seismic Data Gibson, Holliger, Hurich, Levander, Pullammanappallil, … KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008

  18. Imaging & Interpreting CLC Deterministic Probabilistic • Picking up the thread again • Multiple Scattering in a Multi-Scale Medium • Layer-Cake model with von Karman structure • Bi-modal material property (impedance) • Vertical Incidence of P-waves (no conversions) • Can Single-Scattering based Processing work? KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008

  19. Imaging & Interpreting CLC Deterministic Probabilistic Douma & Roy-Chowdhury, 2001 KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008

  20. Imaging & Interpreting CLC Deterministic Probabilistic • The Estimation Problem • 2-D von Karman Medium with ax , az and  • Bi-Modal Lithology (back to the BW problem) • Full-wave seismic response is von Karman too • Medium parameters may be back-estimated Carpentier and Roy-Chowdhury KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008

  21. Imaging & Interpreting CLC Deterministic Probabilistic • The (under)Estimation Problem • Getting Reflectivity from Impedance lowers ax • Estimated ax may be upscaled,  is less robust • Source deconvolution needed to estimate az • Dip Scan improves Estimation for Rotated Blocks Carpentier and Roy-Chowdhury KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008

  22. Imaging & Interpreting CLC Deterministic Probabilistic Dip Scan using a Data-window from the Lithoprobe AG-48 line improves the estimation Carpentier et al KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008

  23. Imaging & Interpreting CLC Deterministic Probabilistic • Got Curious? Visit our Poster (# 72) • Method tried on two Deep Reflection Datasets • Lithoprobe Abitibi-Grenville (AG-48) line • DOBRE 2000/2001 lines in Ukraine! (world is round!) • Results similar to earlier Interpretations • Some interesting differences though • Should help constrain Tectono-Thermal History • Thanks! KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008

  24. Imaging & Interpreting CLC Deterministic Probabilistic AG-48 Carpentier et al KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008

  25. Imaging & Interpreting CLC Deterministic Probabilistic AG-48 Carpentier et al KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008

  26. Imaging & Interpreting CLC Deterministic Probabilistic AG-48 Carpentier et al KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008

  27. Imaging & Interpreting CLC Deterministic Probabilistic AG-48 Carpentier et al KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008

  28. Imaging & Interpreting CLC Deterministic Probabilistic DOBRE 2000/1 Carpentier et al KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008

  29. Imaging & Interpreting CLC Deterministic Probabilistic DOBRE 2000/1 Carpentier et al KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008

  30. Imaging & Interpreting CLC Deterministic Probabilistic DOBRE 2000/1 Carpentier et al KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008

  31. Imaging & Interpreting CLC Deterministic Probabilistic DOBRE 2000/1 Carpentier et al KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008

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