SOURCE/RECEIVER SPACINGS SOURCE/RECEIVER SPACINGS AND THEIR INFLUENCE ON AND THEIR INFLUENCE ON

TOMOGRAMSTOMOGRAMS

Zhiyong JiangZhiyong Jiang

Geology and Geophysics Department Geology and Geophysics Department University of UtahUniversity of Utah

OutlineOutline• MotivationMotivation

• Forward ModelingForward Modeling

• Refraction TomographyRefraction Tomography

• Optimal S/R Spacings Optimal S/R Spacings

• ConclusionsConclusions

220220

1301303290m3290m 3360m3360m

InterfacesInterfacesE

leva

tio

n (

m)

Ele

vati

on

(m

)

X (m)X (m)

Goal:Goal:

Find the Optimal S/R SpacingsFind the Optimal S/R Spacings

0m0m

100m100m0m0m 590m590m

V (m/s)V (m/s)

00

45004500

INCO Velocity ModelINCO Velocity ModelD

epth

(m

)D

epth

(m

)

X (m)X (m)

OutlineOutline• MotivationMotivation

• Forward ModelingForward Modeling

• Refraction TomographyRefraction Tomography

• Optimal S/R Spacings Optimal S/R Spacings

• ConclusionsConclusions

00 590590X (m)X (m)

00

Tim

e (s

)T

ime

(s)

0.30.300 590590X (m)X (m)

Source at (200m, 3.003m)Source at (200m, 3.003m) Source at (400m, 0.427m)Source at (400m, 0.427m)

00 590590X (m)X (m)

00T

ime

(s)

Tim

e (s

)

0.150.15

First Arrivals Auto PickedFirst Arrivals Auto Picked

OutlineOutline• MotivationMotivation

• Forward ModelingForward Modeling

• Refraction TomographyRefraction Tomography

• Optimal S/R Spacings Optimal S/R Spacings

• ConclusionsConclusions

The schedules for dg=4m and ds=8mThe schedules for dg=4m and ds=8m

Smoothing Size (in grid points)Smoothing Size (in grid points) IterationsIterations Grid Size (m)Grid Size (m)

Schedule 1: 48*24Schedule 1: 48*24 1111 0.50.5

Schedule 2: 32*16Schedule 2: 32*16 1111 0.50.5

Schedule 3: 16*8Schedule 3: 16*8 1111 0.50.5

Dynamic SmoothingDynamic Smoothing

dg=4m, ds=8m Schedule 1dg=4m, ds=8m Schedule 1

0m0m

120m120m0m0m 590m590m

V (m/s)V (m/s)

00

45004500

dg=4m, ds=8m Schedule 2dg=4m, ds=8m Schedule 2

0m0m

120m120m0m0m 590m590m

V (m/s)V (m/s)

00

45004500

dg=4m, ds=8m Schedule 3dg=4m, ds=8m Schedule 3

0m0m

120m120m0m0m 590m590m

V (m/s)V (m/s)

00

45004500

dg=4m, ds=8m Schedule 1dg=4m, ds=8m Schedule 1

0m0m

120m120m0m0m 590m590m

Num. of Num. of RaysRays

00

40004000

dg=4m, ds=8m Schedule 2dg=4m, ds=8m Schedule 2

0m0m

120m120m0m0m 590m590m

Num. of Num. of RaysRays

00

40004000

dg=4m, ds=8m Schedule 3dg=4m, ds=8m Schedule 3

0m0m

120m120m0m0m 590m590m

Num. of Num. of RaysRays

00

40004000

Residual vs. Iteration NumberResidual vs. Iteration Number

0000 3535Iteration NumberIteration Number

0.0140.014R

esid

ual

Res

idu

al

Sche 1Sche 1

Sche 2Sche 2Sche 3Sche 3

OutlineOutline• MotivationMotivation

• Forward ModelingForward Modeling

• Refraction TomographyRefraction Tomography

• Optimal S/R Spacings Optimal S/R Spacings

• ConclusionsConclusions

S/R Spacings Tested S/R Spacings Tested

dg (m)dg (m) ds (m)ds (m)

11 2, 42, 4

22 2, 42, 4

44 4, 84, 8

88 8, 168, 16

1212 12, 2412, 24

2424 24, 4824, 48

dg=1m, ds=2mdg=1m, ds=2m

0m0m

120m120m0m0m 590m590m

dg=1m, ds=4mdg=1m, ds=4m

0m0m

120m120m0m0m 590m590m

dg=2m, ds=2mdg=2m, ds=2m

0m0m

120m120m0m0m 590m590m

dg=2m, ds=4mdg=2m, ds=4m

0m0m

120m120m0m0m 590m590m

dg=4m, ds=4mdg=4m, ds=4m

0m0m

120m120m0m0m 590m590m

dg=8m, ds=8mdg=8m, ds=8m

0m0m

120m120m0m0m 590m590m

dg=12m, ds=12mdg=12m, ds=12m

0m0m

120m120m0m0m 590m590m

dg=12m, ds=24mdg=12m, ds=24m

0m0m

120m120m0m0m 590m590m

dg=24m, ds=24mdg=24m, ds=24m

0m0m

120m120m0m0m 590m590m

dg=24m, ds=48mdg=24m, ds=48m

0m0m

120m120m0m0m 590m590m

dg (m)dg (m) ds (m)ds (m)

11 2, 42, 4

22 2, 42, 4

44 4, 84, 8

88 8, 168, 16

1212 12, 12, 2424

2424 24, 4824, 48

High Res.High Res.

Intermediate Res.Intermediate Res.

Poor Res.Poor Res.

S/R Spacings CategorizedS/R Spacings Categorized

dg=2m, ds=2m High Res.dg=2m, ds=2m High Res.

0m0m

120m120m0m0m 590m590m

dg=12m, ds=12 m Interm Res.dg=12m, ds=12 m Interm Res.

0m0m

120m120m0m0m 590m590m

dg=24m, ds=24m Poor Res.dg=24m, ds=24m Poor Res.

0m0m

120m120m0m0m 590m590m

Zoom View, X: 0~200m Zoom View, X: 0~200m

dg=2m, ds=2m High Res.dg=2m, ds=2m High Res.

0m0m

120m120m0m0m 200m200m

dg=12m, ds=12m Interm Res.dg=12m, ds=12m Interm Res.

0m0m

120m120m0m0m 200m200m

dg=24m, ds=24m Poor Res.dg=24m, ds=24m Poor Res.

0m0m

120m120m0m0m 200m200m

Zoom View, X: 200~400m Zoom View, X: 200~400m

dg=2m, ds=2m High Res.dg=2m, ds=2m High Res.

0m0m

120m120m200m200m 400m400m

dg=12m, ds=12m Interm Res.dg=12m, ds=12m Interm Res.

0m0m

120m120m200m200m 400m400m

dg=24m, ds=24m Poor Res.dg=24m, ds=24m Poor Res.

0m0m

120m120m200m200m 400m400m

Zoom View, X 400m~590mZoom View, X 400m~590m

dg=2m, ds=2m High Res.dg=2m, ds=2m High Res.

0m0m

120m120m400m400m 590m590m

dg=12m, ds=12m Interm Res.dg=12m, ds=12m Interm Res.

0m0m

120m120m400m400m 590m590m

dg=24m, ds=24m Poor Res.dg=24m, ds=24m Poor Res.

0m0m

120m120m400m400m 590m590m

OutlineOutline• MotivationMotivation

• Forward ModelingForward Modeling

• Refraction TomographyRefraction Tomography

• Optimal S/R Spacings Optimal S/R Spacings

• ConclusionsConclusions

When ds, dg <= 12m, tomograms When ds, dg <= 12m, tomograms acceptable, resolution high acceptable, resolution high

When ds, dg > 24m, resolution very When ds, dg > 24m, resolution very poor poor

Recommend using ds, dg between Recommend using ds, dg between 1~4 m for good vertical and horizontal 1~4 m for good vertical and horizontal resolutionresolution

ConclusionConclusion

AcknowledgementsAcknowledgements

We thank Utah Tomography and We thank Utah Tomography and Modeling/Migration ConsortiumModeling/Migration Consortium

sponsors for their financial supportsponsors for their financial support