G. Schuster, S. Hanafy, and Y. Huang,

Extracting 200 Hz Information from 50 Hz Data

KAUSTRayleigh Resolution Profile Superresolution Profile

Sincfunction

Spikingfunction

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

Resolution Dx~l/2

L

Z

Δx

Depth

Rayleigh Resolution:

Abbe Resolution:

Super Resolution?:

Dx = lz 4L

Dx = l 2

Dx << l 2

Δx

KAUST yacht

0 km 7 km

0 km

3 km

0 km 7 km

Geophysical Resolution

(Jianhua Yu)

?

Transmission+Reflection Wavepaths(Woodward, 1992)

RTM Resolution: Dx=Rayleigh, Dz=l/4

RTM smile

FWI Resolution: ?

FWI rabbit ears

Z

X

d

Transmission+Reflection Wavepaths(Woodward, 1992)

FWI Resolution:

FWI rabbit earsd

Z

X

FWI Resolution: Dx = 2ld (Williamson, 1991)

3

Transmission+Reflection Wavepaths(Woodward, 1992)

FWI Resolution:

FWI rabbit ears

X

Diff. FWI Resolution: Dxdiff = ld

FWI Resolution: Dx = 2ld (Williamson, 1991) Dx Dxdiff

= 2

d

Benefit: Diffractions transformSSPXwell or VSP DataLiability: SNRdiff << SNRspec

3

Summary

FWI rabbit ears

Diff. FWI Resolution: Dxdiff = ld vs Specular FWI Resolution: Dx =

Benefit: Diffractions transform SSPXwell or VSP DataLiability: SNRdiff << SNRspec

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

Diffraction Waveform Modeling

Born

Modeling

0 Distance (km) 3.8

0D

epth

(km

)1.

20

Dep

th (k

m)

1.2

0tim

e (s

)4.

0

0 Distance (km) 3.8

Velocity

Reflectivity

Scattered CSG

Diffraction Waveform Inversion

0 Distance (km) 3.8

0D

epth

(km

)1.

20

Dep

th (k

m)

1.2

Initial Velocity

Estimated Reflectivity

0D

epth

(km

)1.

2

Inverted Velocity

0 Distance (km) 3.8

0D

epth

(km

)1.

2

True Velocity

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

Mig(z)

Far-field Propagation l-limited Resolutioneiwtxg

l

rG(g|x)=

Time

Mig(z)

Near-field Propagation l/20 Resolutioneiwtxg

l

rG(g|x)=

Time

Note: Time delay unable todistinguish 2 scatterers, butnear-field amplitude changes can: Dx=l/20

Mig(z)

r Evanescent energy

Near-field Propagation l/20 Resolutioneiwtxg

l

rG(g|x)=

Time

Note: Time delay unable todistinguish 2 scatterers, butnear-field amplitude changes can: Dx=l/20

Mig(z)

r Evanescent energy

If source is in farfield of scatterers& geophones in nearfield, superresolution possible

Summary

lTime

Mig(z)

1. Near-field Propagation l/20 Resolution

If source is in nearfield of scatterers& geophones in farfield, superresolution possible

reciprocity

If source is in farfield of scatterers& geophones in nearfield, superresolution possible

1. Near-field Propagation l/20 Resolution

Summary

lTime

Mig(z)

If source is in nearfield of scatterers& geophones in farfield, superresolution possible

reciprocity

If source is in farfield of scatterers& geophones in nearfield, superresolution possible

CRG

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

l

Near-Field Scatterer Images

l

Dx ~ 0.01l

ll

Dx ~ 0.1l

ll

Dx ~ 0.7l

D z ~ 0.1l

ll

25 Near-Field Scatterers Image

l

25 Near-Field Scatterers Image

Migration image at superresolution

l

25 Near-Field Scatterers Image

25 Near-Field Scatterers Image

Vp=1.5 km/sVs=0.75 km/s

Vp=3.0 km/sVs=1.5 km/s

100 m

40 m

Elastic Tunnel Test: 6 Near-Field Scatterers

S wave

P wave

Vp=1.5 km/sVs=0.75 km/s

Vp=3.0 km/sVs=1.5 km/s

100 m

Elastic Tunnel Test: 6 Near-Field Scatterers

S wave

P wave

40 m

No scatterer datascattered data

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

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

Experimental Setup(Not to Scale)Superresolution Test

Goal: Test superresolution imaging by seismic experiment

Experiment: Data with and without a scatterer

0.2 m0.6 m

l=1.6 m

TRM Profiles

l/4 Resolution (110 Hz)

w/o scatterer0.5 m

with scatterer

l/8 Resolution (55 Hz)

with scatterer

0.5 m

220 Hz information from 55 Hz data

Theory

l

Summary

• 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

Diff. FWI Resolution: Dxdiff = ld vs Specular FWI Resolution: Dx =

Possible Applications

VSP: Find local anomalies, faults, and scatterer points around boreholes in VSP data

Ground

Borehole

SSP: Detect local anomalies, faults, and scatterer points around surface

Farfield?

Subduction zone

TRM Profile

Earthquakes along a Fault Detect Fault Roughness

Subduction zone

Earthquakes US Array Detect Near Surface

TRM Profile