Seismic productivity of blasts: A case-study of the Khibiny Massif

Abstract

The authors study the property of production-scale blasts to induce seismic events classified as micro shocks, rock bursts and earthquakes caused by sudden slips along faults. The study area is the production performance zone of Apatit’s Kirovsk Branch. It is situated in the southeast of the Khibiny Massif on the Kola Peninsula and is subjected to continuous autonomous seismicity monitoring. The subject of the research is the production blasts and seismic events recorded by the seismic monitoring station of Apatit’s Kirovsk Branch between January 1996 and June 2019. Blasting-induced seismic events were identified using the nearest neighbor method and the seismicity-dependent proximity function of the space–time–magnitude (energy), calculated with respect to the blasts. The threshold of the proximity function to assume a seismic event as the blast-induced event was selected using the model-independent method of seismic catalog randomization. It is shown that the number of blasting-induced seismic events—blasting productivity—obeys an exponential distribution irrespective of magnitudes or occurrence depths of the studied events. The obtained result conforms with the earlier determined productivity law for natural earthquakes on a global and regional scale, as well as for mining-induced seismicity in the Khibiny Massif. Accordingly, the productivity distribution is governed by the properties of a medium and is independent of the source mechanism of a triggering event (explosion, seismicity). The paper presents the research findings supported by the Russian Foundation for Basic Research, Project No. 19-05-00812, and in the framework of State Contract No. 007-00186-18-00 with the Kola Branch of the Geophysical Service of the Russian Academy of Sciences.

Spatial distribution of blast-triggered seismic events: a case-study of the Khibiny Massif

“…This study continues the research of the authors in the field of time-space patterns of seismic activity in the regions of mineral mining. It is already demonstrated that the number of seismic events triggered by blasting (seismic productivity of blasts) obeys an exponential distribution [1]. It is also found that under conditions of the induced seismicity in the Khibiny Massif, the distances between the seismic events and induced bumps comply with a power-series distribution [2].…”

“…In our study, we consider a single hierarchy scale, and we assume that the events in the series are independent of each other, and in each series, the number of the blast-triggered events with the magnitudes M m t 2 to the earthquake-triggered events with M t M m -1.5 obey the Poisson distribution with an average Λ [25]. In this case, the probability that all triggered events k take place at a distance less than x from a trigger is F r (x) k , where F r (x) is distribution (1). Using the formula of total probability, we obtain a distribution of the maximal epicentral distance R max from a trigger blast to a most remote aftershock in a series:…”

“…As in [1], this study used the catalog of seismic events recorded by the seismic monitoring network of Kirovsk Branch of Apatit [17] from 1996 to 2020, Nowadays the network contains 65 three-component seismic sensors with the sampling frequency of 1000 Hz arranged in Kirovsky and Rasvumchorr Mines. Monitoring enables positioning of hypocenters of seismic events having the energy E t 10 4 J at an accuracy to 25 m in the confident recording region.…”

“…In this algorithm, for each catalogued earthquake, a foregoer is found amongst all preceding blasts by the criterion of the minimum proximity function in the space-time-magnitude (energy) environment. This method of identifying seismic events induced by basting in the Khibiny Massif is described in [1].…”

“…Blasts have no directivity patterns and occur irrespective of the stress level. Therefore, blast triggered events are fewer [1] and their number decays faster as the distance increases from the trigger compared to the case when the trigger is a seismic event.…”