Nanoseismicity and picoseismicity rate changes from static stress triggering caused by a M_w 2.2 earthquake in Mponeng gold mine, South Africa

Abstract

Static stress changes following large earthquakes are known to affect the rate and distribution of aftershocks, yet this process has not been thoroughly investigated for nanoseismicity and picoseismicity at centimeter length scales. Here we utilize a unique data set of M ≥ À3.4 earthquakes following a M w 2.2 earthquake in Mponeng gold mine, South Africa, that was recorded during a quiet interval in the mine to investigate if rate-and state-based modeling is valid for shallow, mining-induced seismicity. We use Dieterich's (1994) rate-and state-dependent formulation for earthquake productivity, which requires estimation of four parameters: (1) Coulomb stress changes due to the main shock, (2) the reference seismicity rate, (3) frictional resistance parameter, and (4) the duration of aftershock relaxation time.Comparisons of the modeled spatiotemporal patterns of seismicity based on two different source models with the observed distribution show that while the spatial patterns match well, the rate of modeled aftershocks is lower than the observed rate. To test our model, we used three metrics of the goodness-of-fit evaluation. The null hypothesis, of no significant difference between modeled and observed seismicity rates, was only rejected in the depth interval containing the main shock. Results show that mining-induced earthquakes may be followed by a stress relaxation expressed through aftershocks located on the rupture plane and in regions of positive Coulomb stress change. Furthermore, we demonstrate that the main features of the temporal and spatial distributions of very small, mining-induced earthquakes can be successfully determined using rate-and state-based stress modeling.

Violations of Gutenberg–Richter Relation in Anthropogenic Seismicity

“…where M is the magnitude value taken from catalog, δM is the length of the magnitude round off interval, u is the random value drawn from the uniform distribution in the with magnitudes from less than -5 up to -0.8 [Kwiatek et al, 2011, Kozłowska, et al, 2015.…”

Earthquake static stress transfer in the 2013 Gulf of Valencia (Spain) seismic sequence

“…Lower threshold values have been reported for anthropogenic seismicity. Orlecka-Sikora (2010) found changes as small as 0.05 bar to be statistically significant in the triggering of events at the Rudna mine in Poland; in another mine-induced seismicity study, Kozlowska et al (2015) also suggest that earthquakes were promoted in areas where CS increased not more than 0.1 bar. With an increase in detection capability and the analysis of smaller earthquakes (lower associated stress drops), it seems that the threshold values diminish.…”

Assessment of Quantitative Aftershock Productivity Potential in Mining-Induced Seismicity

“…This variability may originate from different geomechanical properties of a rock in a seismogenic zone, differences in the main shock's rupture type, geometry and dynamics, but can also be partly controlled by the exploitation parameters. It was already proven that coseismic stress changes caused by strong mining events can influence the following seismicity distribution (Orlecka-Sikora 2010;Orlecka-Sikora et al 2012;Kozłowska et al 2015). Modeling of the seismicity rate, based on Coulomb stress changes and the rate-and-state friction law, can be successfully applied to induced seismicity data and help to predict the spatial and temporal distribution of aftershocks of strong mining events (Kozłowska et al 2015).…”

“…It was already proven that coseismic stress changes caused by strong mining events can influence the following seismicity distribution (Orlecka-Sikora 2010;Orlecka-Sikora et al 2012;Kozłowska et al 2015). Modeling of the seismicity rate, based on Coulomb stress changes and the rate-and-state friction law, can be successfully applied to induced seismicity data and help to predict the spatial and temporal distribution of aftershocks of strong mining events (Kozłowska et al 2015). However, in contrast to natural seismicity, the mining loading is irregular and changes in time.…”

“…Kozłowska et al 2015). To test the Hainzl et al (2010) model and to study the aftershock productivity potential in mining-induced seismicity we applied the proposed forecast to three mining catalogs.…”