No Evidence of Magnitude Clustering in an Aftershock Sequence of Nano- and Picoseismicity

Abstract

One of the hallmarks of our current understanding of seismicity as highlighted by the epidemic-type-aftershock sequence model is that the magnitudes of earthquakes are independent of one another and can be considered as randomly drawn from the Gutenberg-Richter distribution. This assumption forms the basis of many approaches for forecasting seismicity rates and hazard assessment. Recently, it has been suggested that the assumption of independent magnitudes is not valid. It was subsequently argued that this conclusion was not supported by the original earthquake data from California. One of the main challenges is the lack of completeness of earthquake catalogs. Here, we study an aftershock sequence of nano- and picoseismicity as observed at the Mponeng mine, for which the issue of incompleteness is much less pronounced. We show that this sequence does not exhibit any significant evidence of magnitude correlations.

Nontrivial clustering of microseismicity induced by hydraulic fracturing

“…To summarize, this study provides evidence of magnitude clustering in space and time in different microseismic catalogs monitored in three different hydraulic fracture treatments associated with vastly different reservoirs. In contrast, another recent study showed no evidence of magnitude clustering in low magnitudeinduced seismicity that is unrelated to hydraulic fracturing [Davidsen et al, 2012]. This strongly suggests that the magnitude clustering we observe here is a consequence of the specific geometrical constraints of finely laminated shale gas and tight oil reservoirs.…”

“…Here we investigate this question in the broader context of the statistical properties of microseismic activity associated with hydraulic fracturing. Our particular focus is on those properties relevant for forecasting seismicity rates and time‐dependent seismic hazard assessment, namely, magnitude clustering [ Davidsen and Green , ; Davidsen et al , ; Lippiello et al , ] as well as spatiotemporal clustering [ Davidsen and Kwiatek , ; Davidsen et al , ; Davidsen and Baiesi , ; Hainzl et al , ; Moradpour et al , ]. Specifically, we investigate the presence of clustering for three microseismic catalogs recorded at different sites where hydraulic fracturing was performed.…”

Order parameter fluctuations in natural time and <i>b</i>-value variation before large earthquakes

“…Before proceeding to the presentation of our results obtained from the OFC model, we note that concerning the correlations between magnitudes of subsequent earthquakes, there is a diversity of views in the literature. Such correlations, reported by Lippiello et al (2007Lippiello et al ( , 2008, have been later attributed (Davidsen and Green, 2011;Davidsen et al, 2012) to catalog incompleteness. In a subsequent publication, however, Lippiello et al (2012) made an analysis of two California regions with different levels of catalog accuracy and different lower magnitude thresholds, which convincingly indicated that the amplitude of correlations does not depend on catalog incompleteness.…”

Avalanche duration time in a simple heterogeneous Olami–Feder–Christensen model

“…Analysis of some foreshocks has shown that they tend to relieve stress around the fault which is the same mechanism of main earthquake. An aftershock [48,49] is a smaller earthquake that occurs after a previous main earthquake, in the same area of the mainshock. Aftershocks are formed as the crust around the displaced fault plane adjusts to the effects of the mainshock.…”