首页|Can DAS be used to monitor mining induced seismicity?
Can DAS be used to monitor mining induced seismicity?
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NSTL
Elsevier
Distributed acoustic sensing (DAS) is being applied in an increasing number of geoscientific fields. We present herein preliminary results of applying DAS to monitor microseismicity in underground mines. We installed 275 m of fiber optic cable approximately 1500 m below the surface in an operational mine and recorded mine seismicity for two weeks during November of 2018. The first approximately 50 m was tied to the sidewall safety mesh and a further 225 m was grouted into a down-dipping borehole alongside four three-component geophone sensors with 14 Hz high-sensitivity elements. The geophone sensors are located 132 m, 154 m, 176 m and 198 m down the borehole. We show that, for the larger seismic events (MW > -0.1), there is relatively good agreement in the data collected with DAS compared to the geophone data. There is some amplitude variation, especially at higher frequencies, but the phase of the recordings match well. We were able to include the DAS data in processing select events using PhaseNet, a machine-learning based algorithm, to pick phase arrivals and then locate these events using a recently developed interferometric method. In our comparison of the background noise of the DAS and that of the geophones, we found that the DAS as installed in our experiment has a noise floor orders of magnitude higher than the seismic background of the mine. Furthermore we compared the recordings in the different fiber sections (tied to the safety mesh and grouted, respectively) to analyze the feasibility of using existing mining communication infrastructure as sufficiently accurate seismic sensors. Fiber optic communication cables are typically tied to the sidewall mesh in the absence of dedicated conduits, and thus our meshcoupled section was a suitable proxy for this scenario. We found extremely limited utility in the recordings of the mesh coupled fiber.
NSTL
Elsevier
