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Extracting 20 0 Hz Information from 50 Hz Data

Extracting 20 0 Hz Information from 50 Hz Data. G. Schuster, S. Hanafy , and Y. Huang, . KAUST. Sinc function. Spiking function. Rayleigh Resolution Profile. Superresolution Profile. Outline. Motivation: Why Resolution Matters Diffraction vs Specular Resolution: Example

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Extracting 20 0 Hz Information from 50 Hz Data

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  1. Extracting 200 Hz Information from 50 Hz Data G. Schuster, S. Hanafy, and Y. Huang, KAUST Sinc function Spiking function Rayleigh Resolution Profile Superresolution Profile

  2. Outline • Motivation: Why Resolution Matters • Diffraction vs Specular Resolution: Example • Evanescence Resolution • Field Test • Conclusions

  3. Resolution Dx~l/2 L Z Depth Δx Rayleigh Resolution: Δx KAUST yacht Abbe Resolution: Super Resolution?: Dx = Dx = Dx << lz l l 2 2 4L

  4. Geophysical Resolution 0 km 3 km ? (Jianhua Yu) 0 km 7 km 0 km 7 km

  5. Transmission+ReflectionWavepaths (Woodward, 1992) FWI rabbit ears d RTM smile Z RTM Resolution: Dx=Rayleigh, Dz=l/4 FWI Resolution: ? X

  6. Transmission+ReflectionWavepaths (Woodward, 1992) FWI rabbit ears d Z FWI Resolution: X FWI Resolution: Dx= 2ld (Williamson, 1991)

  7. Transmission+ReflectionWavepaths (Woodward, 1992) Diff. FWI Resolution: Dxdiff= ld FWI rabbit ears d 3 FWI Resolution: Benefit: Diffractions transform SSPXwellor VSP Data Liability: SNRdiff << SNRspec X FWI Resolution: Dx= 2ld (Williamson, 1991) Dx =2 Dxdiff

  8. Summary Diff. FWI Resolution: Dxdiff= ldvsSpecular FWI Resolution: Dx = Benefit: Diffractions transform SSPXwellor VSP Data Liability: SNRdiff << SNRspec FWI rabbit ears 3

  9. Outline • Motivation: Why Resolution Matters • Diffraction vs Specular Resolution: Example • Evanescence Resolution • Field Test • Conclusions

  10. Diffraction Waveform Modeling 0 time (s) Born Modeling 4.0 Distance (km) 0 3.8 Scattered CSG Velocity 0 Depth (km) 1.2 Reflectivity 0 Depth (km) 1.2 0 Distance (km) 3.8

  11. Diffraction Waveform Inversion True Velocity 0 Depth (km) 1.2 0 Distance (km) 3.8 Initial Velocity Inverted Velocity 0 0 Depth (km) Depth (km) 1.2 1.2 Estimated Reflectivity 0 Depth (km) 1.2 0 Distance (km) 3.8

  12. Outline • Motivation: Why Resolution Matters • Diffraction vs Specular Resolution: Example • Evanescence Resolution • Field Test • Conclusions

  13. Far-field Propagation  l-limited Resolution eiwtxg G(g|x)= r Mig(z) l Time

  14. Near-field Propagation  l/20 Resolution eiwtxg G(g|x)= r r Evanescent energy Mig(z) Mig(z) Note: Time delay unable to distinguish 2 scatterers, but near-field amplitude changes can: Dx=l/20 l Time

  15. Near-field Propagation  l/20 Resolution eiwtxg G(g|x)= r r Evanescent energy Mig(z) Note: Time delay unable to distinguish 2 scatterers, but near-field amplitude changes can: Dx=l/20 If source is in farfield of scatterers & geophones in nearfield, superresolution possible l Time

  16. Summary 1. Near-field Propagation  l/20 Resolution Mig(z) If source is in farfield of scatterers & geophones in nearfield, superresolution possible reciprocity If source is in nearfield of scatterers & geophones in farfield, superresolution possible l Time

  17. Summary 1. Near-field Propagation  l/20 Resolution CRG Mig(z) If source is in farfield of scatterers & geophones in nearfield, superresolution possible reciprocity If source is in nearfield of scatterers & geophones in farfield, superresolution possible l Time

  18. Outline • Motivation: Why Resolution Matters • Diffraction vs Specular Resolution: Example • Evanescence Resolution • Field Test • Conclusions

  19. Dx ~ Dx ~ 0.1 0.01 0.7 Dx ~  Near-Field Scatterer Images     

  20. D z ~ 0.1 25 Near-Field Scatterers Image  

  21. 25 Near-Field Scatterers Image  Migration image at superresolution

  22. 25 Near-Field Scatterers Image

  23. 25 Near-Field Scatterers Image

  24. Elastic Tunnel Test: 6 Near-Field Scatterers S wave P wave Vp=1.5 km/s Vs=0.75 km/s 40 m Vp=3.0 km/s Vs=1.5 km/s 100 m

  25. Elastic Tunnel Test: 6 Near-Field Scatterers S wave P wave Vp=1.5 km/s Vs=0.75 km/s No scatterer data scattered data 40 m Vp=3.0 km/s Vs=1.5 km/s 100 m

  26. Outline • Motivation: Why Resolution Matters • Diffraction vs Specular Resolution: Example • Evanescence Resolution • Field Test • Conclusions

  27. Experimental Setup (Not to Scale) Superresolution Test Goal: Test superresolution imaging by seismic experiment Experiment: Data with and without a scatterer l=1.6 m

  28. Experimental Setup (Not to Scale) Superresolution Test Goal: Test superresolution imaging by seismic experiment Experiment: Data with and without a scatterer l=1.6 m 0.2 m 0.6 m

  29. TRM Profiles

  30. l/4 Resolution (110 Hz) 0.5 m w/o scatterer with scatterer l/8 Resolution (55 Hz) Theory l with scatterer 0.5 m 220 Hz information from 55 Hz data

  31. Summary Diff. FWI Resolution: Dxdiff= ldvsSpecular FWI Resolution: Dx = • Workflow • 1. Collect Shot gathers G(g|s ), separate scattered field • 2. m(s’) = S G(g,t|s’)* G(g,t|s ) • 3. TRM profiles • Synthetic Results Dx~l/10 • Limitations • Either src or rec in nearfield of subwavelength scatterer • Scattered field separated from specular fields is Big Challenge

  32. Possible Applications SSP: Detect local anomalies, faults, and scatterer points around surface VSP: Find local anomalies, faults, and scatterer points around boreholes in VSP data Farfield? Ground Borehole

  33. Earthquakes along a Fault Detect Fault Roughness Subduction zone TRM Profile

  34. Earthquakes US Array Detect Near Surface Subduction zone TRM Profile

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