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Fault activation and microseismicity in laboratory
experimentsThomas Göbel
Danijel Schorlemmer, Sergei Stanchits, Erik Rybacki
Georg Dresen, Thorsten Becker, Charles Sammis
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1. Changes in spatial and size distributions of seismic events during fault reactivation
2. What type of seismic sources do we expect?
3. Future experiments
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Sample and sensors
Rock specimen with notches
Pressure vessel and loading frame
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Acoustic emission system:
o 16 channelso 10 MHz sampling frequencyo 16 bit resolutiono Piezo-electric sensors with
resonance frequency at 2MHzo Active and passive recordingo Full waveform recording
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Loading curve during fault reactivation
Displacement (mm) Goebel et al. 2012
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Waveforms of small and large events
Goebel et al. 2012
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Typical AE event Large stress drop event
Goebel et al. 2012
Waveforms of small and large events
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AE hypocenter locations
Goebel et al. 2013c
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1. Spatial distribution and b-value
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Lockner et al. 1991
Progressive failure
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AE clustering at different stress levels
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AE clustering at different stress levels
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AE clustering at different stress levels
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Cyclical changes of b-values and stress
Goebel et al. 2013a
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Stress and b-values prior to slip events
Goebel et al. 2013a
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2. Source mechanism
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Fortin et al. 2009
Principle types of acoustic emission in porous media
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Kwiatek & Goebel in prep.
Main source mechanism during stick-slip
Onset of slip event
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Kwiatek & Goebel in prep.
Main source mechanism during stick-slip
Aftershock sequence
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Moment tensors during slip event and aftershock sequence
Shear dominated
Kwiatek & Goebel in prep.
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Thompson et al. 2009
Moment tensors of large magnitude events
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Conclusion• b-values decrease during stress-increase
before fault activation in laboratory analog
• Fractal dimension close to 2 indicate fault related seismicity
• Slip instability is connected to shear-type seismic events
• Frequency content and amplitude spectra are sensitive to fluid content and loading
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3. Future Experiments
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Dresen et al. 2010Pp Pp Pp Pp
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Dresen et al. 2010σ1
PcPc
σ1
Pp Pp Pp Pp
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Dresen et al. 2010σ1
PcPc
σ1
σ1
Pc
σ1
Pp
Pc
Pp Pp Pp Pp
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Dresen et al. 2010σ1
PcPc
σ1
σ1
Pc
σ1
Pp
PpPc
Pp Pp Pp Pp
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Harrington & Benson 2011
Fluid induced eventsMicroseismicity in dry samples
No. Ch.
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Thermally induced cracks vs. shear type events
Low frequency content, monochromatic spectrum
Burlini et al. 2007
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Additional Slides
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Thermally induced cracks vs. shear type events
Low frequency content, monochromatic spectrum
Burlini et al. 2007
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Thermally induced cracks vs. shear type events
Burlini et al. 2007
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Self-similar scaling
Fluid induced eventsMicroseismicity in dry samples
Am
plitu
de
Am
plitu
deNo clear scaling
Harrington & Benson 2011
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D = 2.75D = 2.66D = 2.25
Hirata et al. 1987
Creep tests at constant stress (547 MPa)~ 7 h to failure
Progressivefailure
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Changes in fractal dimension with successive stick-slip events
Goebel et al. 2013b
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Interslip Period Goebel et al. 2013b
Fractal dimension and fault smoothing
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Frac
tal D
imen
sion
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Slip onset
Changes in source mechanism and orientation of principal stressdue to slip
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Attenuation and changes in seismic velocityduring damage accumulation
Stanchits et al. 2003
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Stanchits et al. 2003