1887

Abstract

Summary

To image the rocks and fracture zones between the tunnel and the surface, a surface-tunnelsurface seismic experiment was conducted at the Äspö Hard Rock Laboratory (HRL) in southeastern Sweden. Seismic data were acquired using 333 vertical geophones on the tunnel side, and a three-component MEMS-based seismic landstreamer. Surface part was covered with 75 wireless seismic recorders, enabling simultaneous seismic wavefield sampling on all tunnel and surface seismic receivers. This acquisition geometry enabled excellent data coverage for first arrival tomography, with the velocity model showing good match with known fracture zones intersected in the tunnel and indicating new ones previously unknown. A more focused analysis was conducted along a major fracture zone consisting of three subsets with different hydraulic conductivity intersected in one portion of the tunnel. Here, Vp/Vs, Poisson’s ratio and P- and S-wave seismic quality factors were calculated, with low values of all parameters obtained for the none or low hydraulically conductive fracture sets, while highly hydraulically conductive fracture set shows significantly higher values of all parameters. The studies shown indicate the used acquisition geometry and data handling potential for seismic fracture characterization and show its applicability for different purposes, particularly mining and other subsurface studies.

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/content/papers/10.3997/2214-4609.201800609
2018-02-16
2020-03-31
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References

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