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acoustic emission

Paper on Acoustic Emission activity during hydraulic fracturing experiment in Äspö, Sweden

We published a new paper in the Journal of Geophysical Research: Solid Earth related to the hydraulic fracture experiments performed in 2015 in  Äspö Hard Rock Laboratory, Sweden. Here are the highlights:

  • We analyze source characteristics of picoseismicity (moment magnitudes smaller than -3.5!) related to hydraulic stimulations in Äspö Hard Rock Laboratory, Sweden.
  • We show that spatio-temporal seismicity migration is controlled by changes in hydraulic (pressure times volume) energy.
  • We present that total radiated seismic energy is very low with respect to injected volume, and increases with hydraulic energy rate.

The reference:

Kwiatek, G., Martínez-Garzón, P., Plenkers, K., Leonhardt, M., Zang, A., Specht, S., et al. (2018). Insights Into Complex Subdecimeter Fracturing Processes Occurring During a Water Injection Experiment at Depth in Äspö Hard Rock Laboratory, Sweden. Journal of Geophysical Research: Solid Earth, DOI: 10.1029/2017JB014715. [ Article Page ]

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.