Application of the boundary element method for numerical modelling of the seismic hazard at Bambanani gold mine in South Africa - Abstract

Q: What modelling approach does the paper propose for seismic hazard at Bambanani mine?

The paper applies the boundary element method to represent tabular mining excavations using displacement discontinuity elements, extended with additional discontinuities to capture crush-and-shear-type failures.

Q: How are crush-type and shear-type seismic events evaluated in the model?

Crush-type failures are assessed using the limit equilibrium method with a Hoek-Brown strength criterion, while shear-type failures are assessed using Coulomb-friction strength criteria to features such as Ortlepp-shear and geological structures.

Q: What forecasting period and metrics are used to present modelling results?

The modelling results are presented as time-history analyses of modelled potency from 1 January 2010 to 30 June 2022 and normalised exceedance rates for different mining periods using an upper-truncated power law.

Oct 13, 2026

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This paper presents a novel application of the boundary element method for numerical modelling of seismic activity and hazard associated with shaft pillar extraction at Bambanani mine in South Africa. Tabular mining excavations are represented by displacement discontinuity elements, including additional elements for crush-and-shear failures. Crush-type failures use limit equilibrium with a Hoek-Brown criterion, while shear-type failures use Coulomb-friction strength criteria. Results use time-history potency and normalised exceedance rates for 1 Jan 2010–30 Jun 2022, with relative errors typically below 10–15%, supporting medium- and longer-term forecasting.

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Affiliation: 1Stellenbosch University, South Africa 2Harmony Gold Mine, South Africa 3Institute of Mine Seismology, South Africa Correspondence to: J. Gerber Email: [Jacques.Gerber@IMSeismology.org](Jacques.Gerber@IMSeismology.org) Dates: Received: 14 Jul. 2025 Published: November 2025 How to cite: Gerber, J. , De Koker, N. , Jooste, Y. 2025. Application of the boundary element method for numercial modelling of the seismic hazard at Bambanani gold mine in South Africa. Journal of the Southern African Institute of Mining and Metallurgy, vol. 125, no. 11, pp. 661–674 DOI ID: [https://doi.org/10.17159/2411-9717/875/2025](https://doi.org/10.17159/2411-9717/875/2025) Application of the boundary element method for numerical modelling of the seismic hazard at Bambanani gold mine in South Africa by J. Gerber1,3, N. de Koker1, Y Jooste2 Abstract This paper presentsa novel application of the boundary element method for numerical modelling of the seismic activity and hazard that is associated with the shaft pillar extraction at Bambanani mine in South Africa. In the numerical model, the tabular mining excavations are represented by displacement discontinuity elements, and to accommodate crush, shear, and fault slip seismic events, the numerical model is populated with additional displacement discontinuity elements that represent modelled crush-and shear-type failures in the rockmass. Crush-type failures are evaluated by applying the limit equilibrium method and a Hoek-Brown strength criterion, and shear-type failures are evaluated by applying a Coulomb-friction strength criteria to Ortleppshear and geological features. In this paper, the modelling results are presented as time history analyses of modelled potency from 1 January 2010 to 30 June 2022 and normalised exceedance rates for different mining periods using an upper-truncated power law. The normalised exceedance rates of seismic events that have moment magnitude Mw ≥ 1.0 are lowest for the initial mining period (26 events per year) and highest for the final mining period (218 events per year). The relative errors of the modelled potency and normalised exceedance rates are typically less than 10% or 15%, which suggests that the modelling methodology is appropriate for medium-and longer-term forecasting of seismic activity and hazard, as presented in this paper. Shorter-term forecasting is not considered in this paper. Keywords mine seismology, numerical modelling, boundary element method, seismic hazard Introduction Seismic activity at underground mines is typically associated with fault slip seismic events that occur on geological features and are similar to crustal earthquakes; shear events that occur on stress-induced shear fractures or shear ruptures, e.g., Ortlepp-shear features at the deep gold mines in South Africa (Van Aswegen, 2008), and crush events that occur as stress fracturing or strain bursting in the rockmass that surrounds the mining excavations (Malovichko, 2020; Van Aswegen, 2021a,b; Malovichko, 2022) . From 1 January 2020 to 31 December 2024, the underground seismic systems monitored by the Institute of Mine Seismology (IMS) recorded approximately 1.8 million seismic events that have moment magnitude-1.0 ≤ Mw < 4.0 at fourteen gold mines in the Witwatersrand Basin (Hanks, Kanamori, 1979; Handley, 2004; Tucker et al., 2016; Frimmel, 2019), including 180,834 events that have Mw ≥ 0.0, 19,011 events that have Mw ≥ 1.0, 1,017 events that have Mw ≥ 2.0 and 17 events that have Mw ≥ 3.0. The largest seismic event has moment magnitude Mw = 3.4 and occurred on 16 March 2020 in the Carletonville gold field and the second and third largest events have Mw = 3.3 and occurred on 10 February 2020 and 6 February 2022 in the Carletonville and Klerksdorp gold fields, respectively. Generally, the deep gold mines that extract the tabular orebodies in the Witwatersrand Basin are considered to have significantly higher seismic hazard and th

FAQs

What modelling approach does the paper propose for seismic hazard at Bambanani mine?

The paper applies the boundary element method to represent tabular mining excavations using displacement discontinuity elements, extended with additional discontinuities to capture crush-and-shear-type failures.

How are crush-type and shear-type seismic events evaluated in the model?

Crush-type failures are assessed using the limit equilibrium method with a Hoek-Brown strength criterion, while shear-type failures are assessed using Coulomb-friction strength criteria to features such as Ortlepp-shear and geological structures.

What forecasting period and metrics are used to present modelling results?

The modelling results are presented as time-history analyses of modelled potency from 1 January 2010 to 30 June 2022 and normalised exceedance rates for different mining periods using an upper-truncated power law.

Oct 13, 2026

Upload by Mafia Boss