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.

A paper on spatial distribution of b-value in North Anatolian Fault Zone

The paper on spatial variations of seismic Gutenberg-Richter b-value along the North Anatolian Fault Zone have been recently published in the Tectonophysics.

Reference:

Raub, C., Martínez-Garzón, P., Kwiatek, G., Bohnhoff, M., and G. Dresen (2017). Variations of seismic b-value at different stages of the seismic cycle along the North Anatolian Fault Zone in northwestern Turkey. Tectonophysics 712-713, 232-248, DOI: 10.1016/j.tecto.2017.05.028. [ Article Page ]

New files to download

Thanks to the policy of BSSA, SRL and PRL, I could upload some published versions of the manuscripts I (co-) authored to induced.pl website. [download id=”1832″] This includes the following papers:

Kwiatek, G., Plenkers, K., Nakatani, M., Yabe, Y., Dresen, G., and JAGUARS Research Group (2010). Frequency-magnitude characteristics down to magnitude −4.4 for induced seismicity recorded at Mponeng gold mine, South Africa. Bull. Seismol. Soc. Am., 100(3): 1167–1173, DOI: 10.1785/0120090277.. (791.9 KiB)
Kwiatek, G., Plenkers, K., and G. Dresen (2011). Source parameters of picoseismicity recorded at Mponeng deep gold mine, South Africa: Implications for scaling relations. Bull. Seismol. Soc. Am., 101(6): 2592-2608, DOI: 10.1785/0120110094.. (2.9 MiB)
Plenkers, K., Schorlemmer, D., and G. Kwiatek (2011). On the probability of detecting picoseismicity. Bull. Seismol. Soc. Am., 101(6): 2579-2591, DOI: 10.1785/0120110017.. (771.2 KiB)
Orlecka-Sikora, B., Papadimitriou, E.E., and G. Kwiatek (2010). Study of the interaction among mining induced seismic events in the Legnica-Glogów Copper District, Poland. Acta Geophys., 57(2): 413–434, DOI: 10.2478/s11600-008-0085-z.. (973.3 KiB)
Kwiatek, G., Bohnhoff, M., Dresen, G., Schulze, A., Schulte, T., Zimmermann, G., and E. Huenges (2010). Microseismicity induced during fluid- injection: A case study from the geothermal site at Gross Schoenebeck, North German Basin. Acta Geophys., 58(6): 995–1020, DOI: 10.2478/s11600-010-0032-7.. (1.7 MiB)
Naoi, M., Nakatani, M., Yabe, Y., Kwiatek, G., Igarashi, T., and K. Plenkers (2011). Twenty thousand aftershocks of a very small (M2) earthquake and their relations to the mainshock rupture and geological structures. Bull. Seismol. Soc. Am., 101(5): 2399–2407, DOI: 10.1785/0120100346.. (837.4 KiB)
Davidsen, J., Kwiatek, G., and G. Dresen (2012). No evidence of magnitude clustering in an aftershock sequence of nano- and picoseismicity. Phys. Rev. Lett., 108, 038501, DOI: 10.1103/PhysRevLett.108.038501.. (146.3 KiB)
Davidsen, J., and G. Kwiatek (2013). Earthquake interevent time distribution for induced micro-, nano- and picoseismicity. Phys. Rev. Lett., 110, 068501, DOI: 10.1103/PhysRevLett.110.068501.. (725.1 KiB)

Paper in JGR on improved stress tensor inversion from focal mechanism

Another article related to stress tensor inversion has been published in JGR! This one discusses the improved methodology for stress tensor inversion.

Reference:

Martínez-Garzón, P., Y. Ben-Zion, N. Abofalthian, G. Kwiatek, and M. Bohnhoff (2016). A refined methodology for stress inversions of earthquake focal mechanisms. J. Geophys. Res., 121, 8666-8687, DOI: 10.1002/2016JB013493. [ Article Page ]

Abstract:

We develop an improved methodology for reliable high-resolution inversions of focal mechanisms to background stress field orientation and stress ratio R in two or three dimensions. The earthquake catalog is declustered to remove events likely affected strongly by local stress interactions rather than reflecting the large-scale background stress field. The declustered data are discretized with the k-means algorithm into groups containing a number of focal mechanisms between a minimum number Nmin and 2Nmin. Synthetic tests indicate that Nmin ≈ 30 provides stable inversion results under different stress regimes and noise conditions when R ≈ 0.5, while Nmin ≈ 45 is needed for R near 0 or 1. Additional synthetic tests compare the performance of selecting the fault plane of each focal mechanism using (a) the plane with lowest misfit angle between the slip vector from the focal mechanism and shear traction from the stress tensor and (b) the plane with highest instability coefficient representing proximity to the optimally oriented fault for given stress field and friction coefficient. The instability criterion is found to provide more accurate inversion results under all tested stress regimes, stress ratios, and noise conditions. The refined inversion methodology combines selecting fault planes using the instability criterion iteratively with a damped simultaneous inversion of different focal mechanism groups. Results characterizing neighborhoods of discretized domains merged during the damped inversion provide high-resolution information independent of the discretization. Some aspects of the methodology are illustrated with focal mechanism data from the San Jacinto Fault Zone in Southern California.

Paper in GRL on non-double-couple components at The Geysers geothermal field

Finally we published a paper related to investigation of seismic moment tensors of microseismic events at The Geysers geothermal field.

Reference

Martínez-Garzón, P., Kwiatek, G., Bohnhoff, M., and G. Dresen (2017). Volumetric components in the earthquake source related to fluid injection and stress state. Geophys. Res. Lett. 44, DOI: 10.1002/2016GL071963. [ Article Page ]

Abstract

We investigate source processes of fluid-induced seismicity from The Geysers geothermal
reservoir in California to determine their relation with hydraulic operations and improve the corresponding seismic hazard estimates. Analysis of 869 well-constrained full moment tensors (Mw 0.8–3.5) reveals significant non-double-couple components (>25%) for about 65% of the events. Volumetric deformation is governed by cumulative injection rates with larger non-double-couple components observed near the wells and during high injection periods. Source mechanisms are magnitude dependent and vary significantly between faulting regimes. Normal faulting events (Mw<2) reveal substantial volumetric components indicating dilatancy in contrast to strike-slip events that have a dominant double-couple source. Volumetric components indicating closure of cracks in the source region are mostly found for reverse faulting events with Mw>2.5. Our results imply that source processes and magnitudes of fluid-induced seismic events are strongly affected by the hydraulic operations, the reservoir stress state, and the faulting regime.