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Fault activation and microseismicity in laboratory experiments

Fault activation and microseismicity in laboratory experiments. Thomas Göbel. Georg Dresen , Thorsten Becker, Charles Sammis. Danijel Schorlemmer , Sergei Stanchits , Erik Rybacki. Changes in spatial and size distributions of seismic events during fault reactivation

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Fault activation and microseismicity in laboratory experiments

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  1. Fault activation and microseismicity in laboratory experiments Thomas Göbel Georg Dresen, Thorsten Becker, Charles Sammis DanijelSchorlemmer, Sergei Stanchits, Erik Rybacki

  2. Changes in spatial and size distributions of seismic events during fault reactivation • What type of seismic sources do we expect? • Future experiments

  3. Rock specimen with notches Pressure vessel and loading frame Sample and sensors

  4. Acoustic emission system: • 16 channels • 10 MHz sampling frequency • 16 bit resolution • Piezo-electric sensors with resonance frequency at 2MHz • Active and passive recording • Full waveform recording

  5. Loading curve during fault reactivation Displacement (mm) Goebel et al. 2012

  6. Waveforms of small and large events Goebel et al. 2012

  7. Waveforms of small and large events Goebel et al. 2012 Large stress drop event Typical AE event

  8. AE hypocenter locations Goebel et al. 2013c

  9. 1. Spatial distribution and b-value

  10. Progressive failure Lockner et al. 1991

  11. AE clustering at different stress levels

  12. AE clustering at different stress levels

  13. AE clustering at different stress levels

  14. Cyclical changes of b-values and stress Goebel et al. 2013a

  15. Stress and b-values prior to slip events Goebel et al. 2013a

  16. 2. Source mechanism

  17. Principle types of acoustic emission in porous media Fortin et al. 2009

  18. Main source mechanism during stick-slip Onset of slip event Kwiatek & Goebel in prep.

  19. Main source mechanism during stick-slip Aftershock sequence Kwiatek & Goebel in prep.

  20. Moment tensors during slip event and aftershock sequence Shear dominated Kwiatek & Goebel in prep.

  21. Moment tensors of large magnitude events Thompson et al. 2009

  22. Conclusion • b-values decrease during stress-increasebefore 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

  23. 3. Future Experiments

  24. Pp Pp Pp Pp Dresen et al. 2010

  25. Pp Pp Pp Pp Dresen et al. 2010 σ1 Pc Pc σ1

  26. Pp Pp Pp Pp Dresen et al. 2010 σ1 σ1 Pp Pc Pc Pc Pc σ1 σ1

  27. Pp Pp Pp Pp Dresen et al. 2010 σ1 σ1 Pp Pp Pc Pc Pc Pc σ1 σ1

  28. Fluid induced events Microseismicity in dry samples No. Ch. Harrington & Benson 2011

  29. Thermally induced cracks vs. shear type events Low frequency content, monochromatic spectrum Burlini et al. 2007

  30. - Thank You -

  31. Additional Slides

  32. Thermally induced cracks vs. shear type events Low frequency content, monochromatic spectrum Burlini et al. 2007

  33. Thermally induced cracks vs. shear type events Burlini et al. 2007

  34. Fluid induced events Microseismicity in dry samples No clear scaling Self-similar scaling Amplitude Amplitude Harrington & Benson 2011

  35. Creep tests at constant stress (547 MPa) • ~ 7 h to failure D = 2.75 D = 2.66 D = 2.25 Progressive failure Hirata et al. 1987

  36. Changes in fractal dimension with successive stick-slip events Goebel et al. 2013b

  37. Fractal dimension and fault smoothing Interslip Period Goebel et al. 2013b

  38. Fractal Dimension

  39. Shear dominated

  40. Changes in source mechanism and orientation of principal stress due to slip Slip onset

  41. Attenuation and changes in seismic velocity during damage accumulation Stanchits et al. 2003

  42. Stanchits et al. 2003

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