Homestake Telecon Minutes, 02/25/16

Attending:

Agenda:

• Homestake array
  • status of stations (WTP, Yates, 800)
  • planning next visit: April 15-24
    • No access on Apr 11 (Mon) and Apr 22 (Fri).
    • Replace instruments at 800 and Yates.
    • Harvest data from balers.
    • Clean out the insulation panels being stored in the room at the #4 Winze wye on the 4850L.
    • Terry and Pat will go.
    • Should have one spare instrument, Pat and Tanner should follow up. Need another Guralp from PASSCAL, Gary to follow up on it.
    • Assume to download 4 Balers/day, so need 6 days for the whole array. Checked inventory, looks like we should have 10+ spare balers.

• Data analysis updates
  • Results of the Geochemical Analysis of Homestake Wave Speeds PowerPoint
    • Victor: should follow up on the minerals for which we don't have data. Levi to email the group about them.
    • Velocity does not seem to depend on the depth, so the observed depth dependence of the velocity must come from porosity of the rock, fractures etc.
  • Indiana group results - S velocities and start of event catalogfeb25-2016.pptx
    • Shear wave speed measurements at 2000 level: ~3500 m/s in the Homestake formation, ~3300 m/s in Ellison, and ~3700 m/s in the mixed rock environment near Ross.
    • Victor: any bias due to being close to the tunnel? Gary: possibly, fracturing is probably higher near the tunnels.
    • Gary: looking at anisotropy, but can't tell yet. Need to look at the geology, Levi's work could help with this. Difficult to distinguish anisotropy from heterogeneity in the rock.
    • Event catalog: seeing ~10 events per day, mostly mining explosions in the region. Not all are recovered correctly, need a full array analysis for this.
    • Many large signals with large S-wave contribution from these mining explosions, although one wouldn't expect large S-wave components generated in these explosions.
  • Rayleigh wave planning (Tanner) slides
    • Daniel can help with estimating Rayleigh wave amplitudes, Tanner will follow up with him offline.
    • Daniel: probably best to filter the data in a narrow band around a specific frequency, and then do the fitting. In this way you avoid dealing with different speeds at different frequencies.