Homestake Meeting Minutes, 05/04/17

Attending: Daniel, Gary, Levi, Ross, Vuk, Andrew, Pat, Victor

Agenda:

• Next Meeting: June 1
• Data analysis topics
  • Data corrections, frame production (Gary/Daniel/Pat)
    • Pat: going through the final checks and found that some of the miniSEED files have overlapping times but different data. Not sure what to do, which data to use…
    • Gary: thinks he knows the source of this. We always cleaned the balers before we installed them, but we did do tests in the warehouse which may have left some data in them. Almost positive that these fragments are useless.
    • Could go to original data and check if these files are misplaced.
    • Pat: the first trace in the file is identical to the online data. But there are additional traces, for overlapping times, that look different.
    • Gary: it could be that the Q330 data was mis-assigned to this specific station. In the short term, Pat could move these fragments away, but keep them for Gary to follow up…
    • Pat: we were doing maintenance that week, possible that we swapped the baler at this station that was not perfectly cleaned.
    • Daniel: how often does this happen?
    • Pat: will try to look at the comparison logs…
    • Gary: Will also look at his database.
  • Event catalog (Gary/Ross)
  • Radiometer updates (Pat, Levi)
  • Parameter estimation for Rayleigh and Love (Pat/Levi)
  • Teleseismic events and Wiener filtering (Daniel, Michael)
    • Daniel: gave a talk at a conference (Seismological Society of America, SSA), well received, talked about the Homestake mine, optical timing.
    • Victor: heard that someone else is planning a deployment at Homestake. Not sure of the details.

• Papers
  • Homestake Array Summary paper: pdf
    • Leads: Vuk, Gary, Victor
    • target: Seism. Research Lett., 6000 words, 10 figures.
    • Gary: made some changes, but currently don't have all plots in the paper.
      • Show a figure of all events recorded by the array. Local sources are mostly coming from the same area, and we also see a typical mix of global earthquakes. A figure of this type would be good for this kind of paper.
      • Included a figure of spectrogram of a local blast, from a mine about 2-3 miles away. The above figure does not show these local blasts, but their signals are very large and they are in the data (once per day or so). Could be used to study the wave propagation at relatively high frequencies. So this plot would also be of interest to the overview paper.
      • telefigure.pdf shows an intermediate depth (110 km) in Alaska. The b-plot shows the stack of subarrays, illustrating how the P-wave depends on depth. The c- plot shows the instruments in the 4000 subgroup (and their waveforms match). Plot d shows that the structure comes from ~1 Hz, probably indicating some scattering. This level of complexity is maybe not relevant for this type of paper.
        • Daniel: Sees these plots as a teaser.
        • Gary: probably best to keep only plots a) and b).
        • Victor: agrees, this would give a good overview. Suggest to add some markers for where the P-waves come in. Also, make the ordering “surface” → 2000 → 4000.
        • Gary will do.
        • Decided to go with a) and b)
      • blastfigure.pdf same as above but for a local blast. Shows dramatic difference for P-wave amplitudes as a function of depth, and shows why using subarrays would be useful. Much higher frequency than the teleseismic event in the above figure. Also, teleseismic event is coming from below (so not as much scattering), while the blasts are surface-based and suffer from scattering more.
        • Gary proposes we use only a) and b), others agree.
        • Victor: combine blastfigure.pdf and telefigure.pdf into a single figure.
        • Gary agrees.
      • SlownessVectorFigure.pdf shows that the wavefield propagating from the mines is nearly horizontal. This may explain why the waveforms are complex in blasts. Proposes that we do not include it in the paper.
        • Also, the P-wave traveling along the surface generates an S-wave which is evanescent, decaying with depth. Gary thinks this is visible in the data, in the waveforms: radial amplitudes are the largest (horizontal P-waves).
        • Is this a Rayleigh wave? Not clear, Gary wants to look into this…
        • Victor: it would be useful to write a short note to explain this further.
        • Gary: Yes!
    • Vuk/Victor will try to work on the paper in the coming weeks.

• Active excitation overview paper
  • Leads: Gary, Ross
  • Others: Victor, Daniel,…
  • Will try to add a draft by Apr 13.

• Surface Active Excitation
  • Leads: Victor, Boise
  • Others: Gary, Ross

• Underground Active Excitation:
  • Lead: Gary, Ross

• Parameter estimation for the Rayleigh and Love eigenfunctions (amplitude vs depth dependence).
  • Leads: Pat, Daniel
  • Also contributing: Victor, Vuk, Levi

• Estimating directional and modal composition of the seismic noise. (Pat, Levi, Vuk)
  • Leads: Pat, Vuk, Levi

• Wiener filter application
  • Leads: Jan, Michael

• Teleseismic EQs and near-surface scattering
  • Leads: Daniel, Victor

• Time-variable velocity changes
  • Lead: Victor, not started yet

• Very low frequency harmonics (Ross)