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Paper in BSSA on focal mechanism of small earthquakes from the Salton Sea

Stephan Bentz published paper entitled “Sensitivity of Full Moment Tensors to Data Preprocessing and Inversion Parameters: A Case Study from the Salton Sea Geothermal Field”. The paper presents the results of investigation of mechanisms of approximately 80 small seismic events using two full seismic moment tensor inversion routines: the full waveform inversion and hybridMT code. The paper appeared in the Bulletin of Seismological Society of America.


Bentz, Stephan, P. Martínez-Garzón, G. Kwiatek, M. Bohnhoff, and J. Renner (2018). Sensitivity of Full Moment Tensors to Data Preprocessing and Inversion Parameters: A Case Study from the Salton Sea Geothermal Field, Bull. Seismol. Soc. Am. DOI: 10.1785/0120170203.

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.


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 ]

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.


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 website. This includes the following papers:

Kwiatek, G., P. Martínez-Garzón, and M. Bohnhoff (2016). HybridMT: A MATLAB/Shell Environment Package for Seismic Moment Tensor Inversion and Refinement, Seismol. Res. Lett. 87, no. 4, 964–976, doi 10.1785/0220150251.

[ Download PDF document (1.75 MB) ]

Martínez-Garzón, P., G. Kwiatek, M. Ickrath, and M. Bohnhoff (2014). MSATSI: A MATLAB Package for Stress Inversion Combining Solid Classic Methodology, a New Simplified User- Handling, and a Visualization Tool, Seismol. Res. Lett. 85, no. 4, 896–904, doi 10.1785/0220130189.

[ Download PDF document (9.92 MB) ]

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.

[ Download PDF document (725.13 KB) ]

Davidsen, J., G. Kwiatek, 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.

[ Download PDF document (146.28 KB) ]

Kwiatek, G., K. Plenkers, 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, no. 6, 2592–2608, doi 10.1785/0120110094.

[ Download PDF document (2.88 MB) ]

Plenkers, K., D. Schorlemmer, and G. Kwiatek (2011). On the Probability of Detecting Picoseismicity, Bull. Seismol. Soc. Am. 101, no. 6, 2579–2591, doi 10.1785/0120110017.

[ Download PDF document (771.19 KB) ]

Naoi, M., M. Nakatani, Y. Yabe, G. Kwiatek, T. Igarashi, 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, no. 5, 2399–2407, doi 10.1785/0120100346.

[ Download PDF document (837.38 KB) ]

Kwiatek, G., K. Plenkers, M. Nakatani, Y. Yabe, G. Dresen, and J. 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, no. 3, 1167–1173, doi 10.1785/0120090277.

[ Download PDF document (791.92 KB) ]

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.


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 ]


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.