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Effect of mining and geology on mining-induced seismicity – a case study

Khalil Heba, Chen Tuo, Xu Yu-Hang, Mitri Hani

Journal of Sustainable Mining

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2022

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Vol. 21, iss. 3

200--215

EN

Mining-induced seismicity is a commonly occurring phenomenon in underground mines. This poses a greater challenge to the safety of the mining operation. This paper presents a case study of the Young-Davidson mine in northern Ontario, Canada, where seismic events of magnitude Mn 2.0+ have been observed at mining depths of 600 to 800 m below the surface. The occurrence of large seismic events at such shallow depths is the key issue of this study. A comprehensive study of the microseismic database has been conducted to discern the root causes for the unusually strong seismic activities recorded at shallow depths. The effects of mining activities in the vicinity of two dykes intersecting the orebody on the seismic response are investigated. Variation of the b-value derived from the magnitude-frequency distribution is examined, and moment tensor inversion for three large seismic events is carried out to determine the source mechanisms. It is shown from this investigation that the influence of the sill pillar is more critical, leading to high mining-induced stress and the occurrence of large events. While the findings from this research are specific to this case study, they could be used to shed light on the causes of induced seismicity at other mines with similar conditions.

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Teleseismic moment tensors of the 5 April 2017, Mw6.1, Fariman, northeast Iran, earthquake

Ashtari Jafari Mohammad

Acta Geophysica

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2019

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Vol. 67, no. 2

437--448

EN

On 5 April 2017, an Mw6.1 earthquake occurred about 50 km NE of the city of Fariman, northeast Iran. Several hundreds of aftershocks including two M > 5 events followed the main shock. The quake struck numerous towns and villages across the region, killed one person, and injured tens of people. Many schools and universities were evacuated around the epicentral area, and a lot of people left their residences for a few days. The northeastward motion of the central Iran toward Eurasia influences the epicentral region. Regional movements occur by shortening on the northwest-trending reverse faults. We studied teleseismic source parameters of this earthquake by applying different moment tensor decomposition methods including grid search for the nodal planes of the best double couple; linear inversion for a deviatoric moment tensor; grid search for the best double-couple moment tensor; grid search for the best deviatoric moment tensor; and grid search for the best full moment. Based on the moment tensors, the event occurred on a reverse fault following the regional compressional motion. The results of this study will provide useful information for future regional seismotectonic investigations and are of significant use for applications such as regional seismic hazard evaluations.

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Focal mechanism of earthquakes from the June 1987 swarm in Aswan, Egypt, calculated by the moment tensor inversion

Awad H., Kwiatek G.

Acta Geophysica Polonica

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2005

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Vol. 53, nr 3

275-291

EN

We obtained seismic moment tensor solutions of ten events from the June 1987 earthquake swarm, which occurred along the Kalabsha fault zone in the northern part of the Lake Aswan area in Egypt. In addition, the composite fault plane solution of this sequence was also calculated. The waveform data were obtained from the Aswan seismological network, which consists of 13 field stations with short period seismometers GS-13. The June 1987 swarm was a sequence of microearthquakes (M ? 3.4), shallow (0-10 km) events forming two successive bursts, which took place on June 17 and 19. The moment tensor solutions indicate that the focal mechanisms of events from this swarm sequence are expressed by right-lateral strike slip faults. They represent also an effective east-west compressional stress field acting in the area. Geological and geophysical data demonstrate that the Kalabsha fault zone is a right-lateral strike slip fault that consists of several fault segments trending in the east-west direction, perpendicular to the axis of the main course of the Lake As-wan. Thus, the focal mechanisms of the 1987 events are consistent with the local tectonics of the area.

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Focal mechanism and source time function of selected aftershocks of the Egion 1995 earthquake, Gulf of Corinth, Greece

Gibowicz S., Domański B., Wiejacz P.

Acta Geophysica Polonica

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1999

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Vol. 47, nr 1

1-25

EN

Numerous aftershocks, which followed the 1995 Egion earthquake of magnitude Ms = 6.2, were recorded by the seismic network PATNET of the University of Patras and by a temporary local network EGINET. The well recorded aftershocks were located by the Patras Seismological Centre, University of Patras. The complete data set, received from the Centre, contains the records of over a hundred events. The spatial distribution of their epicentres forms an E-W elongated cloud with a central cluster and a few stray-away epicentres west and north-west from the cloud. The events from the central cluster, which is the source area of the main shock, that occurred during the first decade of August 1995, were selected for the analysis. Additionally, a few events from the small cluster located west of the main one were also analysed. Altogether, it was possible to perform the moment tensor inversion in the time domain for 29 aftershocks from the main cluster and for 4 events from the small cluster. The selected aftershocks have moment magnitude ranging from 1.7 to 3.2. The source time function of the larger events was determined by the empirical Green's function technique. The records of several pairs of large-small aftershocks, close to each other and with similar focal mechanism, were selected for deconvolution. The source time function was recovered for 5 larger aftershocks from the central cluster and for 3 events from the small cluster. The small number of available stations used for the moment tensor inversion limit stable results to the constrained double couple solutions. The solutions show a mixture of various types of the focal mechanism, though dip-slip events prevail over strike-slip events, and normal faulting prevails over reverse faulting. The pulse widths of relative source time functions depend on the station azimuth, indicating that the ruptures propagated unilaterally. The azimuth of rupture direction ranges from about 90 to 250 degrees with the dominant direction of about 200 degrees. The fracture velocity ranges from 0.4 to 0.8 of the shear wave velocity. The obtained results indicate complexity of the stress distribution in the source area of the Egion earthquake.