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Seismicity induced by longwall coal mining at the Thoresby Colliery, Nottinghamshire, U.K.

Research output: Contribution to journalArticle

Original languageEnglish
Pages (from-to)942-954
Number of pages13
JournalGeophysical Journal International
Volume212
Issue number2
Early online date25 Oct 2017
DOIs
DateAccepted/In press - 24 Oct 2017
DateE-pub ahead of print - 25 Oct 2017
DatePublished (current) - 1 Feb 2018

Abstract

The United Kingdom has a long history of deep coal mining, and numerous cases of mininginduced seismicity have been recorded over the past 50 yr. In this study, we examine seismicity induced by longwall mining at one of the United Kingdom's last deep coal mines, the Thoresby Colliery, Nottinghamshire. After public reports of felt seismicity in late 2013 a local seismic monitoring network was installed at this site, which provided monitoring from February to October 2014. This array recorded 305 seismic events, which form the basis of our analysis. Event locations were found to closely track the position of the mining face within the Deep Soft Seam, with most events occurring up to 300 m ahead of the face position. This indicates that the seismicity is being directly induced by the mining, as opposed to being caused by activation of pre-existing tectonic features by stress transfer. However, we do not observe correlation between the rate of excavation and the rate of seismicity, and only a small portion of the overall deformation is being released as seismic energy. Event magnitudes do not follow the expected Gutenberg-Richter distribution. Instead, the observed magnitude distributions can be reproduced if a truncated power-law distribution is used to simulate the rupture areas. The best-fitting maximum rupture areas correspond to the distances between the Deep Soft Seam and the seams that over- and underlie it, which have both previously been excavated. Our inference is that the presence of a rubble-filled void (or goaf) where these seams have been removed is preventing the growth of larger rupture areas. Source mechanism analysis reveals that most events consist of dip-slip motion along nearvertical planes that strike parallel to the orientation of the mining face. These mechanisms are consistent with the expected deformation that would occur as a longwall panel advances, with the under- and overburdens moving upwards and downwards respectively to fill the void created by mining. This further reinforces our conclusion that the events are directly induced by the mining process. Similar mechanisms have been observed during longwall mining at other sites.

    Research areas

  • Earthquake source observations, Geomechanics, Induced seismicity, Seismic anisotropy

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  • Full-text PDF (accepted author manuscript)

    Rights statement: This is the author accepted manuscript (AAM). The final published version (version of record) is available online via Oxford University Press at https://academic.oup.com/gji/article/212/2/942/4564775 . Please refer to any applicable terms of use of the publisher.

    Accepted author manuscript, 2 MB, PDF-document

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