ambient noise tomography fundamentals
TRANSCRIPT
Ambient Noise Tomographyfundamentals
Christoph Sens-Schonfelder
GFZ German Research Centre for Geosciences, Potsdam, Germany
4DMB meeting, 2.2.2018
Recap
tomographic techniques:
I refraction tomography
I local or teleseismic earthquake tomography
I surface wave tomography
common approach
Infer information about the medium from the observableinteraction of a wavefied during the propagation from its source toa set of receivers.
Recap
source-receiver geometry
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We can directly measure the impulse response (Green’s function).
Recap
Recap
Seismic records
Signals from impulsive localized sources make up a tiny fraction ofthe records only. Most of it is NOISE.
Seismic records
Signals from impulsive localized sources make up a tiny fraction ofthe records only. Most of it is NOISE.
Seismic records
Signals from impulsive localized sources make up a tiny fraction ofthe records only. Most of it is NOISE.
The ambient wavefield
am
plit
ude
timede
pth
surface
How to make use of these random oscillations?
The ambient wavefield
am
plit
ude
timede
pth
surface
How to make use of these random oscillations?
The ambient wavefield
am
plit
ude
timede
pth
surface
How to make use of these random oscillations?
The ambient wavefield
am
plit
ude
timede
pth
surface
How to make use of these random oscillations?
The ambient wavefield
am
plit
ude
timede
pth
surface
How to make use of these random oscillations?
The ambient wavefield
am
plit
ude
timede
pth
surface
How to make use of these random oscillations?
The ambient wavefield
am
plit
ude
timede
pth
surface
How to make use of these random oscillations?
The ambient wavefield
am
plit
ude
timede
pth
surface
How to make use of these random oscillations?
The ambient wavefield
am
plit
ude
timede
pth
surface
How to make use of these random oscillations?
The ambient wavefield
am
plit
ude
timede
pth
surface
How to make use of these random oscillations?
The ambient wavefield
am
plit
ude
timede
pth
surface
How to make use of these random oscillations?
The ambient wavefield
am
plit
ude
timede
pth
surface
How to make use of these random oscillations?
The ambient wavefield
am
plit
ude
timede
pth
surface
How to make use of these random oscillations?
Seismic Interferometry (SI)
Use the correlation properties of the field – not the field itself!
impulsive source
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random sources
One can create data for tomography from random fields bycorrelating records from different locations!
Seismic Interferometry (SI)
Use the correlation properties of the field – not the field itself!
impulsive source
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
random sources
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
One can create data for tomography from random fields bycorrelating records from different locations!
Seismic Interferometry (SI)
Use the correlation properties of the field – not the field itself!
impulsive source
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
random sources
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
One can create data for tomography from random fields bycorrelating records from different locations!
Seismic Interferometry (SI)
Use the correlation properties of the field – not the field itself!
impulsive source
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
random sources
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
One can create data for tomography from random fields bycorrelating records from different locations!
Seismic Interferometry (SI)
Use the correlation properties of the field – not the field itself!
impulsive source
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
random sources
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
One can create data for tomography from random fields bycorrelating records from different locations!
Seismic Interferometry (SI)
Use the correlation properties of the field – not the field itself!
impulsive source
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
random sources
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
One can create data for tomography from random fields bycorrelating records from different locations!
Seismic Interferometry (SI)
Use the correlation properties of the field – not the field itself!
impulsive source
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
random sources
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
One can create data for tomography from random fields bycorrelating records from different locations!
Seismic Interferometry (SI)
Use the correlation properties of the field – not the field itself!
impulsive source
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
random sources
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
One can create data for tomography from random fields bycorrelating records from different locations!
Seismic Interferometry (SI)
Use the correlation properties of the field – not the field itself!
impulsive source
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
random sources
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
One can create data for tomography from random fields bycorrelating records from different locations!
Seismic Interferometry (SI)
Use the correlation properties of the field – not the field itself!
impulsive source
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
random sources
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
One can create data for tomography from random fields bycorrelating records from different locations!
Seismic Interferometry (SI)
Green’s functions extraction:
G (xB , xA, t) + G (xB , xA,−t) ∝∫S
G (xB , x, t) + G (xA, x,−t)dS
Application 1: coda correlation
[Campillo and Paul, 2003]
Application 1: coda correlation
particle motion
[Campillo and Paul, 2003]
retrieve surface waves from earthquake coda
Application 2: coda correlation in an array
Green’s tensor
[Paul et al., 2005]
Application 3: noise correlation
[Wapenaar et al., 2010]
Application 3: noise correlation
dispersion
[Shapiro and Campillo, 2004]
First summarySeismic interferometry
I uses records of a random wavefield that contains the requiredwaves
I waves propagating between receivers are extracted from therandom field by cross correlation
I allows to retrieve surface waves traveling between seismicstations
Some review papers on SI:
I [Snieder, 2004]
I [Campillo, 2006]
I [Curtis et al., 2006]
I [Wapenaar et al., 2010]
I [Snieder and Larose, 2013]
Application 4: ambient noise surface wave tomography
group velocity maps of Southern California
7.5 s 15 s
[Shapiro et al., 2005]
What is the ambient noise?power spectrum of a typical noise record (New Mexico)
[Peterson, 1993]
What is the ambient noise?power spectrum of a typical noise record (New Mexico)
[Peterson, 1993]
Microtremorvibrations with f > 1Hz mostly of cultural origin (traffic, industry,wind turbines)
[Bonnefoy-Claudet et al., 2006]
Microseisms
seismic waves excited by the action of ocean waves
Microseisms
seismic waves excited by the action of ocean waves
I hum and primary microseisms around 12 s period: interferenceof waves with ocean bottom topography
Microseisms
seismic waves excited by the action of ocean waves
I hum and primary microseisms around 12 s period: interferenceof waves with ocean bottom topography
I secondary (double frequency) microseism around 6 s period:wave-wave interaction
Microseisms
seismic waves excited by the action of ocean waves
I hum and primary microseisms around 12 s period: interferenceof waves with ocean bottom topography
I secondary (double frequency) microseism around 6 s period:wave-wave interaction
The source site effect due to the water depth modulates theefficiency of seismic wave generation.
Seismic sources are neither simply below wind systems nor at theshore!
Source regions of secondary microseisms
[Landes et al., 2010]
Consequences for tomography
I source distribution is variable ⇒ potenial for estimates ofwave velocities
[Froment et al., 2010]
⇒ long time averaging required to reduce the effect ofnon-uniform source distributions.
Summary
I seismic interferometry allows to retrieve the Green’s functionfrom random seismic fields (e.g. ambient noise)
I the ambient field below 0.3 Hz is generated in the oceans(microseisms)
I high frequency cultural noise above 1 Hz
⇒ allows for surface wave tomography without individuallyidentified sources
I uneven source distribution can bias velocity estimates
References
Bonnefoy-Claudet, S., Cotton, F., and Bard, P. Y. (2006).The nature of noise wavefield and its applications for site effects studies. Aliterature review.Earth-Science Rev., 79(3-4):205–227.
Campillo, M. (2006).Phase and Correlation in ‘Random’ Seismic Fields and the Reconstruction of theGreen Function.Pure Appl. Geophys., 163(2-3):475–502.
Campillo, M. and Paul, A. (2003).Long-range correlations in the diffuse seismic coda.Science, 299(5606):547–9.
Curtis, A., Gerstoft, P., Sato, H., Snieder, R., and Wapenaar, K. (2006).Seismic interferometry – turning noise into signal.Lead. Edge, 25(9):1082.
Froment, B., Campillo, M., Roux, P., Gouedard, P., Verdel, A., and Weaver,R. L. (2010).Estimation of the effect of nonisotropically distributed energy on the apparentarrival time in correlations.Geophysics, 75(5):SA85.
Landes, M., Hubans, F., Shapiro, N. M., Paul, A., and Campillo, M. (2010).Origin of deep ocean microseisms by using teleseismic body waves.J. Geophys. Res. Solid Earth, 115(5):1–14.
Paul, A., Campillo, M., Margerin, L., Larose, E., and Derode, A. (2005).Empirical synthesis of time-asymmetrical Green functions from the correlation ofcoda waves.J. Geophys. Res., 110(B8):B08302.
Peterson, J. (1993).Observations and modeling of seismic background noise.USGS Open File Rep., 93-322:Open–File Report 93–322.
Shapiro, N. and Campillo, M. (2004).Emergence of broadband Rayleigh waves from correlations of the ambientseismic noise.Geophys. Res. Lett., 31:7614.
Shapiro, N. M., Campillo, M., Stehly, L., and Ritzwoller, M. H. (2005).High-resolution surface-wave tomography from ambient seismic noise.Science (80-. )., 307(5715):1615–1618.
Snieder, R. (2004).Extracting the Green’s function from the correlation of coda waves: A derivationbased on stationary phase.Phys. Rev. E, 69(4):046610.
Snieder, R. and Larose, E. (2013).Extracting Earth’s Elastic Wave Response from Noise Measurements.Annu. Rev. Earth Planet. Sci., 41(1):183–206.
Wapenaar, K., Draganov, D., and Snieder, R. (2010).Tutorial on seismic interferometry: Part 1—Basic principles and applications.Geophysics, 75(5).