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GEOPHYSICAL RESEARCH LETTERS, VOL. 32, L05308, doi:10.1029/2004GL021733, 2005

Relative location of excavation induced microseismicity at the Underground Research Laboratory (AECL, Canada) using surveyed reference events

J. M. Reyes-Montes

Department of Earth and Ocean Sciences, University of Liverpool, Liverpool, UK


A. Rietbrock

Department of Earth and Ocean Sciences, University of Liverpool, Liverpool, UK


D. S. Collins

Lassonde Institute, University of Toronto, Toronto, Ontario, Canada


R. P. Young

Lassonde Institute, University of Toronto, Toronto, Ontario, Canada


Abstract

Microseismicity is extensively used to monitor induced damage accumulation and stability of underground structures. Classical location routines in this context can often not resolve the potential coalescence of the induced microcracks, since the location accuracy is on the order of magnitude of the largest fractures observed. Most of the uncertainty arises from the poor knowledge of the seismic velocity field. Master event relocation techniques can circumvent this problem and significantly improve the accuracy in hypocenter determination. We relocate events recorded during the excavation of the TSX tunnel at the Underground Research Laboratory (URL) and show that the resolution is enhanced by up to one order of magnitude. The relocated events locate closer to the excavation perimeter than the absolute locations, a result that corresponds with the observed damage. Additionally the relocated events define a clearer structure, with planes of alignment parallel to the tunnel perimeter.

Received 12 October 2004; accepted 7 February 2005; published 12 March 2005.

Index Terms: 0935 Exploration Geophysics: Seismic methods (3025, 7294); 7215 Seismology: Earthquake source observations (1240); 7294 Seismology: Seismic instruments and networks (0935, 3025); 7299 Seismology: General or miscellaneous.

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Citation: Reyes-Montes, J. M., A. Rietbrock, D. S. Collins, and R. P. Young (2005), Relative location of excavation induced microseismicity at the Underground Research Laboratory (AECL, Canada) using surveyed reference events, Geophys. Res. Lett., 32, L05308, doi:10.1029/2004GL021733.