Fault Detection by a Seismic Scanning Tunneling Macroscope

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Fault Detection by a Seismic Scanning Tunneling Macroscope
Extracting 200 Hz Information from
50 Hz Data
G. Schuster, S. Hanafy, and Y. Huang,
KAUST
Rayleigh Resolution Profile
Sinc
function
Superresolution Profile
Spiking
function
Outline
•
•
•
•
•
Motivation: Why Resolution Matters
Diffraction vs Specular Resolution: Example
Evanescence Resolution
Field Test
Conclusions
Resolution Dx~l/2
L
Depth
Z
Δx
Δx
Rayleigh Resolution: Dx =
KAUST yacht
Abbe Resolution: Dx =
Super Resolution?: Dx <<
lz
4L
l
2
l
2
Geophysical Resolution
0 km
?
(Jianhua Yu)
3 km
0 km
7 km
0 km
7 km
Transmission+Reflection Wavepaths
(Woodward, 1992)
FWI rabbit ears
d
Z
RTM smile
RTM Resolution: Dx=Rayleigh, Dz=l/4
FWI Resolution: ?
X
Transmission+Reflection Wavepaths
(Woodward, 1992)
FWI rabbit ears
d
Z
FWI Resolution: Dx = √2ld (Williamson, 1991)
X
Transmission+Reflection Wavepaths
(Woodward, 1992)
Diff. FWI Resolution: Dxdiff = √ld
FWI rabbit ears
3
d
Dx
= √2
Dxdiff
FWI Resolution: Dx = √2ld (Williamson, 1991)
Benefit: Diffractions transform
SSPXwell or VSP Data
Liability: SNRdiff << SNRspec
X
Summary
Diff. FWI Resolution: Dxdiff = √ld vs Specular FWI Resolution: Dx = 𝟐l𝒅
Benefit: Diffractions transform SSPXwell or VSP Data
Liability: SNRdiff << SNRspec
3
FWI rabbit ears
Outline
•
•
•
•
•
Motivation: Why Resolution Matters
Diffraction vs Specular Resolution: Example
Evanescence Resolution
Field Test
Conclusions
Diffraction Waveform Modeling
Scattered CSG
Born
Reflectivity
Modeling
4.0
Depth (km) 0
1.2
0
time (s)
1.2
Depth (km) 0
0
Velocity
Distance (km)
3.8
0
Distance (km)
3.8
Diffraction Waveform Inversion
1.2
True Velocity
1.2
1.2
Depth (km) 0
Depth (km) 0
Estimated Reflectivity
0
Inverted Velocity
1.2
Depth (km) 0
Depth (km) 0
Initial Velocity
Distance (km)
3.8
0
Distance (km)
3.8
Outline
•
•
•
•
•
Motivation: Why Resolution Matters
Diffraction vs Specular Resolution: Example
Evanescence Resolution
Field Test
Conclusions
Far-field Propagation  l-limited Resolution
G(g|x)=
iwt
e xg
r
Mig(z)
Time
l
Near-field Propagation  l/20 Resolution
G(g|x)=
iwt
e xg
r
Evanescent energy
Mig(z)
Mig(z)
Note: Time delay unable to
distinguish 2 scatterers, but
near-field amplitude changes can:
Dx=l/20
Time
l
Near-field Propagation  l/20 Resolution
G(g|x)=
iwt
e xg
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
Time
l
Summary
1. Near-field Propagation  l/20 Resolution
Mig(z)
If source is in farfield of scatterers
& geophones in nearfield,
superresolution possible
reciprocity
Time
l
If source is in nearfield of scatterers
& geophones in farfield,
superresolution possible
Summary
1. Near-field Propagation  l/20 Resolution
CRG
Mig(z)
If source is in farfield of scatterers
& geophones in nearfield,
superresolution possible
reciprocity
Time
l
If source is in nearfield of scatterers
& geophones in farfield,
superresolution possible
Outline
•
•
•
•
•
Motivation: Why Resolution Matters
Diffraction vs Specular Resolution: Example
Evanescence Resolution
Field Test
Conclusions
Near-Field Scatterer Images
Dx ~ 0.01l
l
l
Dx ~ 0.1l
l
l
Dx ~0.7l
l
l
25 Near-Field Scatterers Image
D z ~0.1l
l
25 Near-Field Scatterers Image
l
Migration image at superresolution
25 Near-Field Scatterers Image
l
25 Near-Field Scatterers Image
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
Elastic Tunnel Test: 6 Near-Field Scatterers
S
wave
P wave
Vp=1.5 km/s
Vs=0.75 km/s
No scatterer data
40 m
scattered
data
Vp=3.0 km/s
Vs=1.5 km/s
100 m
Outline
•
•
•
•
•
Motivation: Why Resolution Matters
Diffraction vs Specular Resolution: Example
Evanescence Resolution
Field Test
Conclusions
Experimental
Setup
Superresolution Test
(Not to Scale)
Goal: Test superresolution imaging by seismic
experiment
Experiment: Data with and without a scatterer
l=1.6 m
Experimental
Setup
Superresolution Test
(Not to Scale)
Goal: Test superresolution imaging by seismic
experiment
Experiment: Data with and without a scatterer
l=1.6 m
0.2 m
0.6 m
TRM Profiles
l/4 Resolution (110 Hz)
0.5 m
w/o scatterer
with scatterer
l/8 Resolution (55 Hz)
Theory
l
0.5 m
with scatterer
220 Hz information from 55 Hz data
Summary
Diff. FWI Resolution: Dxdiff = √ld vs Specular FWI Resolution: Dx = 𝟐l𝒅
• 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
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
Earthquakes along a Fault Detect Fault
Roughness
Subduction zone
TRM Profile
Earthquakes US Array Detect Near Surface
Subduction zone
TRM Profile

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