The validity of Es/Ep as a source parameter in mining seismology

Wesseloo, Johan; Potvin, Yves

doi:10.36487/acg_rep/1952_29_morkel

Cited by 4 publications

(6 citation statements)

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“…The reliability of E S / E P ratios as an indicator of source mechanism has recently been questioned by Morkel et al . [83]. Shearing sources are expected to have f oP / f oS > 1 (table 2).…”

Section: Discussionmentioning

confidence: 99%

“…The reliability of E S / E P ratios as an indicator of source mechanism has recently been questioned by Morkel et al . [83].…”

Section: Discussionmentioning

confidence: 99%

“…However, E S /E P for the crush source with the stope and rigid pillar mimics that of a shearing source indicating that this parameter may not be as definitive a source descriptor as is widely thought. The reliability of E S /E P ratios as an indicator of source mechanism has recently been questioned by Morkel et al [83]. (8) Shearing sources are expected to have f oP /f oS > 1 (table 2).…”

Section: (A) Comparison Of the Input And Inferred Source Parametersmentioning

confidence: 99%

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Complexities of underground mining seismic sources

Linzer

Hildyard

Wesseloo

2021

Phil. Trans. R. Soc. A.

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This paper presents a numerical investigation on the influence of the mining environment on seismic sources, with a focus on pillar failure mechanisms in tabular mining. We investigate the influence of the mining stope (underground excavation or void) on seismic inversions for the scalar moment, corner frequency, source radius, stress drop and moment tensor using synthetic events created within elastodynamic numerical modelling software, WAVE3D. The main objective is to determine whether the source parameters calculated from the recorded waveforms are due to a combination of the stope source and the pillar sources, rather than being related only to crushing of the pillar or shearing in the pillar footwall. The main finding is that the presence of stopes, and types of pillars, have a significant impact on the seismic moment and other source parameters. This is important since the moment is viewed as a robust parameter on which seismic magnitude is often based; however, this study indicates that moments calculated for pillar failure in a tabular stoping environments are less representative of the shearing or crushing source than originally thought. This article is part of the theme issue ‘Fracture dynamics of solid materials: from particles to the globe’.

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Section: Discussionmentioning

confidence: 99%

“…The reliability of E S / E P ratios as an indicator of source mechanism has recently been questioned by Morkel et al . [83].…”

Section: Discussionmentioning

confidence: 99%

Section: (A) Comparison Of the Input And Inferred Source Parametersmentioning

confidence: 99%

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Complexities of underground mining seismic sources

Linzer

Hildyard

Wesseloo

2021

Phil. Trans. R. Soc. A.

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“…The estimated source mechanism using the Es/Ep ratio (Morkel et al 2019) showed that 70 out of 83 large events and seven out of eight very large events had a non-shear source mechanism using Es/Ep = 10 as a boundary between non-shear and shear events. Figures 8 and 9 show the locations of the non-shear and shear large events within 0.5 magnitude intervals.…”

Section: Dynamic Source Parametersmentioning

confidence: 99%

Large seismic events (M > 0) in the Lappberget orebody, Garpenberg, Sweden: blast or non-blast-related?

Güçlü¹,

Dineva²,

Mozaffari³

et al. 2020

Proceedings of the Second International Conference on Underground Mining Technology

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The definition of large magnitude events for mining-induced seismicity highly depends on the general pattern of seismicity in the underground mine. The seismic system in the underground Garpenberg Mine, located in Sweden, was installed in June 2012. In total, 40,000 events were recorded by the end of 2018 with the largest event of magnitude M 2.3. The large seismic events in Garpenberg Mine are defined as the events with M > 0 and very large events with M > 1. This study is based on data from the Lappberget orebody from 2012 to the end of 2018. A seismically active zone was defined in the Lappberget orebody on the northeast side with approximately 90% of the seismicity. The larger magnitude events occurred mostly in this zone too. The large events occurred at depth above 1,000 m, and the so-called very large seismic events, above 750 m. The events in the upper levels, above 700 m, are characterised by comparatively lower apparent stress than the events below. It was found that 24 % of the large seismic events were triggered by production blasts within 24 hours and 150 m. Most of the blast-related large events occurred within two hours after blasting. Only a few large seismic events had intense aftershocks. The aftershock series lasts for around 10 hours and are within 150 m of the main shock. In case of more a complicated situation with blast relation and multiple large events, the aftershock series lasts more than 60 hours. Based on the observations made here, some simple rules were defined for closing mine areas after large seismic events (so-called re-entry protocol for large seismic events). The reasonable restriction after the large seismic event would be three hours with a 150 m radius from the hypocentre of the large seismic event. The duration might be extended depending on the pattern of the aftershock sequence, especially for the large seismic events that occurred after blasting. In this case, the procedure of re-entry protocol for post-blast sequences must be followed. The obtained information about the relation between the large events and blasting can be used also for the re-entry protocol after blasting.

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“…(1998), Kwiatek and Ben‐Zion (2013), Morkel et al. (2019), Liu et al. (2020), Rebuli and Kohler (2014) and Sweby et al.…”

Section: Introductionmentioning

confidence: 99%

Using legacy 3D seismic data and source parameters of mining‐induced earthquakes to mitigate the risk of rockbursting in Kloof Gold Mine, South Africa

Masethe

Manzi

Durrheim

2023

Geophysical Prospecting

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Rockbursts pose a significant risk in deep gold mines in the Witwatersrand Basin of South Africa as they may damage the excavation, injure workers, and delay production. We analysed the source mechanisms of 75 large mining‐related seismic events (ML 1.5–2.7) that caused damage to stopes in Kloof Gold Mine and used legacy 3D reflection seismic data to delineate the ore body and geological structures that may be correlated with mining‐related seismic events. The 75 seismic events took place at depths of 1600–4200 m below surface. Most events were located close to stopes mining the Ventersdorp Contact Reef ore body. The S‐to‐P‐wave energy ratio (Es/Ep) from the analysed seismic events ranged from 1.1 to 19.9. The source mechanisms of mining‐induced seismic events aid in understanding the dominant modes of failure. Planes of weakness may be the result of mining‐induced stresses or pre‐existing geological structures such as faults and dykes. The Es/Ep ratio, focal mechanism and moment tensor solutions were correlated to the underground mapped and seismically defined geological structures. Approximately 44% of the events showed strong correlation with the known underground mapped and seismically imaged geological structures (faults and dykes), whereas 56% of the events were related to elements of the mining geometry (dip pillars, abutments and remnants). This information enables mining layouts to be modified to minimize the risk of rockbursting.

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The validity of Es/Ep as a source parameter in mining seismology

Cited by 4 publications

References 10 publications

Complexities of underground mining seismic sources

Complexities of underground mining seismic sources

Large seismic events (M > 0) in the Lappberget orebody, Garpenberg, Sweden: blast or non-blast-related?

Using legacy 3D seismic data and source parameters of mining‐induced earthquakes to mitigate the risk of rockbursting in Kloof Gold Mine, South Africa

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