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

2. 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

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

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

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

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

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

9. AE hypocenter locations Goebel et al. 2013c

10. 1. Spatial distribution and b-value

11. Lockner et al. 1991 Progressive failure

12. AE clustering at different stress levels

13. AE clustering at different stress levels

14. AE clustering at different stress levels

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

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

17. 2. Source mechanism

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

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

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

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

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

23. Conclusion b-values decrease during stress-increase before fault activation in laboratory analog b-values decrease during stress-increase before fault activation in laboratory analog Fractal dimension close to 2 indicate fault related seismicity Fractal dimension close to 2 indicate fault related seismicity Slip instability is connected to shear-type seismic events Slip instability is connected to shear-type seismic events Frequency content and amplitude spectra are sensitive to fluid content and loading Frequency content and amplitude spectra are sensitive to fluid content and loading

24. 3. Future Experiments

25. Dresen et al. 2010 PpPp PpPp PpPp PpPp

26. σ1σ1 PcPc PcPc σ1σ1 PpPp PpPp PpPp PpPp

27. σ1σ1 PcPc PcPc σ1σ1 σ1σ1 PcPc σ1σ1 PpPp PcPc PpPp PpPp PpPp PpPp

28. σ1σ1 PcPc PcPc σ1σ1 σ1σ1 PcPc σ1σ1 PpPp PpPp PcPc PpPp PpPp PpPp PpPp

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

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

31. - Thank You -

32. Additional Slides

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

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

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

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

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

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

39. Fractal Dimension

40. Shear dominated

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

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