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.,
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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.
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