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acoustic emission

Paper in Geology on fault roughness

Together with Thomas Goebel and other co-authors we published a paper in Geology on fault roughness in laboratory stick-slip experiments on rock samples.

Reference:

Goebel, T.H.W., Kwiatek, G., Becker, T.W., Brodsky, E.E. and G. Dresen (2017). What allows seismic events to grow big?: Insights from b-value and fault roughness analysis in laboratory stick-slip experiments. Geology 45 (9): 815-818, DOI: 10.1130/G39147.1 [ Article Page ]

New paper on triggering processes in rock fracture experiments

We published a new manuscript in Physical Review Letters on triggering processes in laboratory experiments on rock samples (with implications to natural and induced seismicity of course!)

Reference

Davidsen, J., Kwiatek, G., Charalampidou, E.-M., Goebel, T., Stanchits, S., Rueck, M., and G. Dresen. Triggering processes in rock fracture. Phys. Res. Lett. 119, 068501, DOI: 10.1103/PhysRevLett.119.068501. [ Article Page ]

Abstract: We study triggering processes in triaxial compression experiments under a constant displacement rate on sandstone and granite samples using spatially located acoustic emission events and their focal mechanisms. We present strong evidence that event-event triggering plays an important role in the presence of large-scale or macrocopic imperfections, while such triggering is basically absent if no significant imperfections are present. In the former case, we recover all established empirical relations of aftershock seismicity including the Gutenberg-Richter relation, a modified version of the Omori-Utsu relation and the productivity relation—despite the fact that the activity is dominated by compaction-type events and triggering cascades have a swarmlike topology. For the Gutenberg-Richter relations, we find that the b value is smaller for triggered events compared to background events. Moreover, we show that triggered acoustic emission events have a focal mechanism much more similar to their associated trigger than expected by chance.

On acoustic emissions, moment tensors and anisotropy

We have published a paper related to the analysis of seismic moment tensors of acoustic emission data with a special focus on effects of rock anisotropy on resulting moment tensors.

Stierle, E., V. Vavryčuk, G. Kwiatek, E.-M. Charalampidou, and M. Bohnhoff (2016). Seismic moment tensors of acoustic emissions recorded during laboratory rock deformation experiments: sensitivity to attenuation and anisotropy, Geophysical Journal International 205, no. 1, 38–50, doi 10.1093/gji/ggw009.

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Article on moment tensors and b values from acoustic emissions

Finally, the paper on seismic moment tensors and b-values calculated for acoustic emissions has been published in Geophysical Research Letters. Here is the link and reference to the paper:

Kwiatek, G., Goebel, T., and G. Dresen (2014). Seismic moment tensor and b value variations over successive seismic cycles in laboratory stick-slip experiments. Geophys. Res. Lett. 41, DOI: 10.1002/2014GL060159. [ Article page ]

 

 

Another paper on Acoustic Emission

We published a paper in European Journal of Environmental and Civil Engineering on analysis of acoustic emission data in fracture and fluid-injection experiments in sandstone. Here is the reference:

Kwiatek, G., Charalampidou, E.-M., Dresen, G., and S. Stanchits (2014). An improved method for seismic moment tensor inversion of acoustic emissions through assessment of sensor coupling and sensitivity to incidence angle. Int. J. Rock Mech. Min. Sci. 65, 153-161, DOI: 10.1016/j.ijrmms.2013.11.005 [ Article Page ]

Abstract:

We performed laboratory experiments on sandstone specimens to study brittle failure and the reactivation of an experimentally produced failure plane induced by pore-pressure perturbations using constant force control in high compressive stress states. Here, we focus on the shear failure of a dry sample and the later on induced fracture plane reactivation due to water injection. Acoustic Emission (AE) monitoring has been used during both experiments. We also used ultrasonic wave velocities to monitor pore fluid migration through the initially dry specimen. To characterise AE source mechanisms, we analysed first motion polarities and performed full moment tensor inversion at all stages of the experiments. For the case of water injection on the dry specimen that previously failed in shear, AE activity during formation of new fractures is dominated by tensile and shear sources as opposed to the fracture plane reactivation, when compressive and shear sources are most frequent. Furthermore, during the reactivation of the latter, compressive sources involve higher compressive components compared to the shear failure case. The polarity method and the moment tensor inversion reveal similar source mechanisms but the latter provides more information on the source components.