dsx-08 saariselka june 8-13, 2008 imaging & interpreting continental lower crust: from potential...
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DSX-08 Saariselka June 8-13, 2008DSX-08 Saariselka June 8-13, 2008
IMAGING & INTERPRETINGCONTINENTAL LOWER CRUST:
FROM POTENTIAL PROBLEMS TO PROBABLE PROCESSES
Kabir Roy-ChowdhuryUtrecht University, The Netherlands
KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008
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
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
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
Imaging & Interpreting CLC Deterministic Probabilistic
Processing DSS records
KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008
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
Imaging & Interpreting CLC Deterministic Probabilistic
Gibbs, 1986
KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008
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
Imaging & Interpreting CLC Deterministic Probabilistic
Kong et al, 1985
KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008
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
Imaging & Interpreting CLC Deterministic Probabilistic
Phinney & Roy-Chowdhury, 1989
KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008
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
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
Imaging & Interpreting CLC Deterministic Probabilistic
Hansen et al, 1988
KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008
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
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
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
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
Imaging & Interpreting CLC Deterministic Probabilistic
Douma & Roy-Chowdhury, 2001
KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008
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
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
Imaging & Interpreting CLC Deterministic Probabilistic
Carpentier et al
Dip Scan using a Data-window from the Lithoprobe AG-48 line improves the estimation
KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008
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
Imaging & Interpreting CLC Deterministic Probabilistic
Carpentier et al
AG-48
KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008
Imaging & Interpreting CLC Deterministic Probabilistic
Carpentier et al
AG-48
KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008
Imaging & Interpreting CLC Deterministic Probabilistic
Carpentier et al
AG-48
KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008
Imaging & Interpreting CLC Deterministic Probabilistic
Carpentier et al
AG-48
KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008
Imaging & Interpreting CLC Deterministic Probabilistic
Carpentier et al
DOBRE 2000/1
KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008
Imaging & Interpreting CLC Deterministic Probabilistic
Carpentier et al
DOBRE 2000/1
KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008
Imaging & Interpreting CLC Deterministic Probabilistic
Carpentier et al
DOBRE 2000/1
KRC, Department of Earth Sciences DSX-08: Saariselka, June 8-13, 2008
Imaging & Interpreting CLC Deterministic Probabilistic
Carpentier et al
DOBRE 2000/1