Source mechanisms of mine-related seismicity, Savuka mine, South Africa

Jordi Julià, Andrew Arnold Nyblade, Ray Durrheim, Lindsay Linzer, Rengin Gök, William Walter, Paul Dirks

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

We report full moment tensor solutions for 76 mine tremors with moment magnitudes (Mw) between 0.5 and 2.6 recorded by a network of 20 high-frequency geophones in a deep gold mine in South Africa. Source mechanisms convey important information on how in-mine stresses are relaxed, and understanding the nature of such mechanisms is essential for improving our assessment of rock mass response to mining. Our approach has consisted of minimizing the L2 norm of the difference between observed and predicted P, SV, and SH spectral amplitudes, with visually assigned polarities, to constrain all six independent components of the seismic moment tensor. Our results reveal the largest principal stresses in the mine are com pressive, oriented near vertically, and relaxed through a mix of volumetric closure and normal faulting, consistent with a gravity-driven closure of the mined-out areas. Previous moment tensor studies in deep mines had suggested that the distribution of seismic sources in terms of the volumetric-shear mix was bimodal. A bimodal distribution is compatible with our moment tensor solutions only for moment magnitudes above 2.2. Events in the 0:5 <Mw <2:2 moment magnitude range display a continuous distribution of their volumetric-shear mix.

Original languageEnglish (US)
Pages (from-to)2801-2814
Number of pages14
JournalBulletin of the Seismological Society of America
Volume99
Issue number5
DOIs
StatePublished - Oct 1 2009

Fingerprint

moment tensor
Republic of South Africa
Tensors
seismicity
moments
tensors
rock mass response
Seismographs
Gold mines
Faulting
geophone
seismic moment
seismic source
gold mine
closures
Gravitation
faulting
shear
Rocks
tremors

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology

Cite this

Julià, Jordi ; Nyblade, Andrew Arnold ; Durrheim, Ray ; Linzer, Lindsay ; Gök, Rengin ; Walter, William ; Dirks, Paul. / Source mechanisms of mine-related seismicity, Savuka mine, South Africa. In: Bulletin of the Seismological Society of America. 2009 ; Vol. 99, No. 5. pp. 2801-2814.
@article{491d442abb80451d922eb48c363a4442,
title = "Source mechanisms of mine-related seismicity, Savuka mine, South Africa",
abstract = "We report full moment tensor solutions for 76 mine tremors with moment magnitudes (Mw) between 0.5 and 2.6 recorded by a network of 20 high-frequency geophones in a deep gold mine in South Africa. Source mechanisms convey important information on how in-mine stresses are relaxed, and understanding the nature of such mechanisms is essential for improving our assessment of rock mass response to mining. Our approach has consisted of minimizing the L2 norm of the difference between observed and predicted P, SV, and SH spectral amplitudes, with visually assigned polarities, to constrain all six independent components of the seismic moment tensor. Our results reveal the largest principal stresses in the mine are com pressive, oriented near vertically, and relaxed through a mix of volumetric closure and normal faulting, consistent with a gravity-driven closure of the mined-out areas. Previous moment tensor studies in deep mines had suggested that the distribution of seismic sources in terms of the volumetric-shear mix was bimodal. A bimodal distribution is compatible with our moment tensor solutions only for moment magnitudes above 2.2. Events in the 0:5 <Mw <2:2 moment magnitude range display a continuous distribution of their volumetric-shear mix.",
author = "Jordi Juli{\`a} and Nyblade, {Andrew Arnold} and Ray Durrheim and Lindsay Linzer and Rengin G{\"o}k and William Walter and Paul Dirks",
year = "2009",
month = "10",
day = "1",
doi = "10.1785/0120080334",
language = "English (US)",
volume = "99",
pages = "2801--2814",
journal = "Bulletin of the Seismological Society of America",
issn = "0037-1106",
publisher = "Seismological Society of America",
number = "5",

}

Source mechanisms of mine-related seismicity, Savuka mine, South Africa. / Julià, Jordi; Nyblade, Andrew Arnold; Durrheim, Ray; Linzer, Lindsay; Gök, Rengin; Walter, William; Dirks, Paul.

In: Bulletin of the Seismological Society of America, Vol. 99, No. 5, 01.10.2009, p. 2801-2814.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Source mechanisms of mine-related seismicity, Savuka mine, South Africa

AU - Julià, Jordi

AU - Nyblade, Andrew Arnold

AU - Durrheim, Ray

AU - Linzer, Lindsay

AU - Gök, Rengin

AU - Walter, William

AU - Dirks, Paul

PY - 2009/10/1

Y1 - 2009/10/1

N2 - We report full moment tensor solutions for 76 mine tremors with moment magnitudes (Mw) between 0.5 and 2.6 recorded by a network of 20 high-frequency geophones in a deep gold mine in South Africa. Source mechanisms convey important information on how in-mine stresses are relaxed, and understanding the nature of such mechanisms is essential for improving our assessment of rock mass response to mining. Our approach has consisted of minimizing the L2 norm of the difference between observed and predicted P, SV, and SH spectral amplitudes, with visually assigned polarities, to constrain all six independent components of the seismic moment tensor. Our results reveal the largest principal stresses in the mine are com pressive, oriented near vertically, and relaxed through a mix of volumetric closure and normal faulting, consistent with a gravity-driven closure of the mined-out areas. Previous moment tensor studies in deep mines had suggested that the distribution of seismic sources in terms of the volumetric-shear mix was bimodal. A bimodal distribution is compatible with our moment tensor solutions only for moment magnitudes above 2.2. Events in the 0:5 <Mw <2:2 moment magnitude range display a continuous distribution of their volumetric-shear mix.

AB - We report full moment tensor solutions for 76 mine tremors with moment magnitudes (Mw) between 0.5 and 2.6 recorded by a network of 20 high-frequency geophones in a deep gold mine in South Africa. Source mechanisms convey important information on how in-mine stresses are relaxed, and understanding the nature of such mechanisms is essential for improving our assessment of rock mass response to mining. Our approach has consisted of minimizing the L2 norm of the difference between observed and predicted P, SV, and SH spectral amplitudes, with visually assigned polarities, to constrain all six independent components of the seismic moment tensor. Our results reveal the largest principal stresses in the mine are com pressive, oriented near vertically, and relaxed through a mix of volumetric closure and normal faulting, consistent with a gravity-driven closure of the mined-out areas. Previous moment tensor studies in deep mines had suggested that the distribution of seismic sources in terms of the volumetric-shear mix was bimodal. A bimodal distribution is compatible with our moment tensor solutions only for moment magnitudes above 2.2. Events in the 0:5 <Mw <2:2 moment magnitude range display a continuous distribution of their volumetric-shear mix.

UR - http://www.scopus.com/inward/record.url?scp=70349860156&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=70349860156&partnerID=8YFLogxK

U2 - 10.1785/0120080334

DO - 10.1785/0120080334

M3 - Article

AN - SCOPUS:70349860156

VL - 99

SP - 2801

EP - 2814

JO - Bulletin of the Seismological Society of America

JF - Bulletin of the Seismological Society of America

SN - 0037-1106

IS - 5

ER -