![Page 1: Comparison of MEMS accelerometers and …...Comparison of MEMS accelerometers and geophones at Spring Coulee, Alberta Author Michael Hons and Rob Stewart Subject CREWES Research Report](https://reader035.vdocument.in/reader035/viewer/2022071106/5fe0853160a2b549c95c27b3/html5/thumbnails/1.jpg)
Comparison of MEMS
accelerometers and
geophones at Spring
Coulee, Alberta
Michael Hons and Rob Stewart
CREWES Sponsors Meeting 2008
Canmore, Alberta
![Page 2: Comparison of MEMS accelerometers and …...Comparison of MEMS accelerometers and geophones at Spring Coulee, Alberta Author Michael Hons and Rob Stewart Subject CREWES Research Report](https://reader035.vdocument.in/reader035/viewer/2022071106/5fe0853160a2b549c95c27b3/html5/thumbnails/2.jpg)
Outline
• Data correction
• Field Data
• Comparisons
– Corrected data
– Crosscorrelation
– Noise window comparison
– Trace coherence
• Conclusions
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Motion sensing
Rayleigh waves
![Page 4: Comparison of MEMS accelerometers and …...Comparison of MEMS accelerometers and geophones at Spring Coulee, Alberta Author Michael Hons and Rob Stewart Subject CREWES Research Report](https://reader035.vdocument.in/reader035/viewer/2022071106/5fe0853160a2b549c95c27b3/html5/thumbnails/4.jpg)
Geophones
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Geophone response
t
U
it
X2
00
2
2
2
![Page 6: Comparison of MEMS accelerometers and …...Comparison of MEMS accelerometers and geophones at Spring Coulee, Alberta Author Michael Hons and Rob Stewart Subject CREWES Research Report](https://reader035.vdocument.in/reader035/viewer/2022071106/5fe0853160a2b549c95c27b3/html5/thumbnails/6.jpg)
Geophone response
2
2
2
00
2 2 t
U
i
i
t
X
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MEMS accelerometer
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MEMS accelerometer
2
2
2
00
2 2
1
t
U
iX
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MEMS accelerometer
2
2
2
0
1
t
UX
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Geophone/Accelerometer
transfer
G
G
S
Vi
t
U )(2 22
00
2
2
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Field Data• 54 dynamite shots, 40 receivers
• All receivers through Sercel system
• Receivers every 10 m, shots every 30 m
• Maximum offset: 1500 m
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Field Data• 54 dynamite shots, 40 receivers
• All receivers through Sercel system
• Receivers every 10 m, shots every 30 m
• Maximum offset: 1500 m
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Acceleration receiver gathers
• Acceleration domain, vertical component
• Coupling problems at some stations
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Acceleration receiver gathers
• Not everywhere
• Reflections very similar
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Acceleration traces
• Visually, very similar
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Acceleration traces
• Visually, very similar
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Crosscorrelations• 3 Hz lowcut
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• 3 Hz lowcut + 60 Hz highcut
Crosscorrelations
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Amplitude spectra
• Very similar at well-planted stations
• Similar overall, larger low-f in DSUs
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Amplitude spectra
• Very similar at well-planted stations
• Similar overall, larger low-f in DSUs
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Amplitude spectra
• Very similar at well-planted stations
• Similar overall, larger low-f in DSUs
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Noise-only spectra
• Before first break arrivals
• Cross-over around 70-80 Hz
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Far-offset SNR
• From traces with >450 ms noise record
• Spectrum from reflection window divided
by spectrum from noise window
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F-X coherency plot
• No major differences evident
• Geophone more coherent at low-f?
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F-X coherency plot
• No major differences evident
• Geophone more coherent at low-f?
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S/N estimate
• Window 6 traces wide, 500 ms long
• Value plotted at centre of window
• DSU advantage near, geophone
advantage far
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S/N estimate
• Window 6 traces wide, 500 ms long
• Value plotted at centre of window
• DSU advantage near, geophone
advantage far
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Time/frequency analysis
• Geophones more coherent at low-f
• Fairly even over dominant frequencies
• Higher S/N at high-f in DSU, 1-2.5 sec
•5-20 Hz
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Time/frequency analysis
• Geophones more coherent at low-f
• Fairly even over dominant frequencies
• Higher S/N at high-f in DSU, 1-2.5 sec
•20-35 Hz
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Time/frequency analysis
• Geophones more coherent at low-f
• Fairly even over dominant frequencies
• Higher S/N at high-f in DSU, 1-2.5 sec
•50-65 Hz
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Conclusions
• Some coupling problems evident for DSUs
• Where well-coupled, data is similar
• Where reliable noise record available, cross-over exists ~70-80 Hz– Similar crossover in S/N
• No evidence of better signal at very low-frequencies in vertical component
• Early suggestions:– geophones may be better for lower frequency far-
offset or late arrivals
– DSUs may be better for higher frequency near-offset or shallow arrivals
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Acknowledgements
• All those who contributed to the Spring
Coulee experiment
• Glenn Hauer and Malcolm Bertram
• All the CREWES sponsors