Field Investigation of Mining-Induced Seismicity on Local Geohydrologyby Simon M. Hsiung, Cent for Nuclear Waste Regulatory, Analyses, San Antonio, United States,
Wilson Blake, Cent for Nuclear Waste Regulatory, Analyses, San Antonio, United States,
Asadul H. Chowdhury, Cent for Nuclear Waste Regulatory, Analyses, San Antonio, United States,
Jacob Philip, Cent for Nuclear Waste Regulatory, Analyses, San Antonio, United States,
Abstract: Hydraulic response of the rock mass due to earthquakes is one of the concerns in the assessment of the long-term performance of a repository. Studies performed by other researchers indicated no systematic difference between natural earthquakes and mining-induced seismic events. The purpose of this field study at the Lucky Friday Mine is intended to obtain a better understanding regarding the local geohydrologic changes due to mining-induced seismicity and to evaluate analytical methods for simulation of these changes. Three saturated zones with faults and vein features were packed-off along a borehole drilled at approximately 20° downward in a southerly direction from a depth about 1,737 m (5,700 ft) below surface for water pressure monitoring. The response of water pressure change to mine seismicity is found to be more pronounced in Zone 3, which contains the Lucky Friday Main Vein, than Zone 2, with the South Control Fault, and Zone 1, with the associated fractures parallel to the South Control Fault. The maximum observed pressure increase in Zone 3 was about 1.53 × 10-2 MPa (2.22 psi) due to a seismic event to Richter magnitude 3.0 with a source distance about 274.3 m (900 ft) from the location of the Lucky Friday Main Vein. Observed water drops in Zone 1 resulting from a number of seismic events are suspected to be related to slips along the associated fractures of the South Control Fault, or the South Control Fault itself, which initiated the seismic events. Water pressure increase in Zone 3 was found to be a function of event magnitude and distance.
Subject Headings: Seismic tests | Seismic effects | Water pressure | Field tests | Geological faults | Rock masses | Mines and mining | Hydraulics
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