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 {{:groups:homestake:meetings:results_of_the_geochemical_analysis_of_homestake_wavespeeds.pdf|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 catalog{{:groups:homestake:meetings:feb25-2016.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) {{:groups:homestake:meetings:2016_02_25_rayleigh_waves.pdf|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.