A novel frequency-dependent Multi-Offset Phase Analysis (MOPA) … · 2017. 3. 15. · Vignoli et al., 2015. Surface waves V S [m/s] borehole consolidated layers 26 Vignoli et al.,

A novel frequency-dependent Multi-Offset

Phase Analysis (MOPA) of Surface Waves:

Theory and Applications

Giulio Vignoli Geological Survey of Denmark and Greenland - GEUS

Isabella Gervasio Università di Trieste

Giuseppe Brancatelli Università di Trieste

Jacopo Boaga Università di Padova

Bruno Della Vedova Università di Trieste

Giorgio Cassiani Università di Padova

GNGTS, Trieste,19 November 2015 1

Outlines

1.The frequency-dependent Multi-Offset Phase

Analysis (MOPA)

2.An example

3.Conclusions

2

Outlines

1.The frequency-dependent Multi-Offset Phase

Analysis (MOPA)

2.An example

3.Conclusions

3

offset [m]

tim

e [s]

0 100 200 300 400 500

0

1

2

3

600

0.05 0.15 0.25 0.35 0.45

10m/s

wavenumber

[1/m]

freq

ue

nc

y[H

z]

1) seismogram

2) f-k spectrum

3) dispersion curve

ph

as

e v

el.

[m/s

]

freq. [Hz]

200 300 400 500 600

0

2

4

6

8

10

12

S-wave vel. [m/s]

de

pth

[m

]4) inversion

5101520253035404550

4

m

xkti

m

m

m

mexB

xsxs

))()(( 0),(

),(),(

5

m

xkti

m

m

m

mexB

xsxs

))()(( 0),(

),(),(

)( )(),( 0 xkx m

6

),()(),( 0 imii xkx

with receivers:

.,...,1 Ni

N

1D

f1=8Hz

f2=36Hz

f3=50Hz

[ra

d]

[m] 7

),()(),( 0 imii xkx

with receivers:

.,...,1 Ni

N

sharp lateral

discontinuity

f1=8Hz

f2=36Hz

f3=50Hz

[ra

d]

[m] 8

f1=8Hz

f3=50Hz

f2=36Hz

),()(),( 0 imii xkx

with receivers:

.,...,1 Ni

N

2D

[ra

d]

[m] 9

Vs [m/s]

10

Vignoli et al., 2011

VR [m/s]

11

Vignoli et al., 2011

40

30

20

10

Fre

qu

en

cy [

Hz]

350

340

330

320

310

300

290

280

270

VR [m/s]

20 30 40 50 60 70

X [m]80

12

40

30

20

10

Fre

qu

en

cy [

Hz]

350

340

330

320

310

300

290

280

270

VR [m/s]

20 30 40 50 60 70

X [m]80

13

40

30

20

10

Fre

qu

en

cy [

Hz]

350

340

330

320

310

300

290

280

270

VR [m/s]

20 30 40 50 60 70

X [m]80

14

Outlines

1.The frequency-dependent Multi-Offset Phase

Analysis (MOPA)

2.An example

3.Conclusions

15

Torre

creek

Isonzo

river

Turriaco

(Gorizia)

Survey

area

N-E Italy:

Isonzo River and Torre creek

riparian zone

16

ERT

17

10000

6309

3981

2511

1584

1000631

398200

158100

ERT

very resistive inclusion: ~ 5000 m

18

10000

6309

3981

2511

1584

1000631

398200

158100

ERT

very resistive inclusion: ~ 5000 m

19

10000

6309

3981

2511

1584

1000631

398200

158100

ERT

very resistive inclusion: ~ 5000 m

20

10000

6309

3981

2511

1584

1000631

398200

158100

VP [m/s]

Refraction

21

VP [m/s]

Refraction

22

VP [m/s]

Refraction

23

Surface waves

24

Surface wavesVS [m/s]

25

Vignoli et al., 2015

Surface wavesVS [m/s]

borehole

consolidated

layers 26

Vignoli et al., 2015

VP [m/s]

Refraction

27

10

00

0

63

09

39

81

25

11

15

84

10

00

63

1

39

82

00

15

81

00

28

Outlines

1.The frequency-dependent Multi-Offset Phase

Analysis (MOPA)

2.An example

3.Conclusions

29

30

1.Discussion of a Frequency-dependent Multi-Offset

Phase Analysis (MOPA) approach for surface

waves:

• high resolution in the shallow part, and

• robustness at depth.

2.Application to a very shallow environment, and

comparison against:

• Borehole data,

• Refraction seismic results, and

• ERT.