Homestake Meeting Minutes, 01/26/17

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

Agenda:

- Paper plans

• Possible papers discussed in past meetings:
  • Data report paper (everyone)
    • practical issues uncovered in the active source experiments.
    • It will double as a data report required by IRIS.
    • This probably should also include the weight drop experiment.
    • Publication options are a new AGU journal Earth and Space that encourages this kind of paper. Alternatively, Seismological Research Letters recently announced it will consider similar papers.
  • Boise/Caltech on surface active excitation
    • Determine what goes in which paper.
  • Similar paper on the 3D array
    • SRL might be more appropriate for this one as it has a higher impact factor, and is appropriate for papers without very deep science, more speculative things.
    • Show some data in this paper, such as the seismic noise levels, variation over time, variation with depth, maybe coherence plots. No significant data analysis, just basic things.
  • Discussion of the above papers:
    • Gary: maybe should consolidate into one paper, or potentially two (3D array and active excitation)
    • Victor: the Boise group has a paper near complete, maybe no need to have it in the summary paper.
    • Gary/Victor to contact Gabe to determine how to proceed.
    • Vuk: try to put together a draft of the summary paper. In Word, using dropbox. Goal to have a draft in 1 month, by the next telecon.
    • Gary will send Vuk an outline he prepared for active excitation.
    • Then the active excitation paper(s) can reference the summary paper.

• Parameter estimation for the Rayleigh and Love eigenfunctions (amplitude vs depth dependence).
  • Pat, Daniel, Victor, Vuk, Levi
  • Pat and Daniel will lead it
  • This could be a separate paper, or a part of the above paper.
  • Include inversion (using velocity structure) and parameter estimation (probably)

• Estimating directional and modal composition of the seismic noise. (Pat, Levi, Vuk)
  • This would include the radiometer method description, some simulations, and applications to real data IF we manage to convince ourselves that the method is working.
  • Try this first at low frequencies (0.1 Hz), maybe compare with other existing techniques. And then work upwards in frequency until things start to break.
  • For an estimate of the modal and directional composition of the seismic noise, compute the estimate of Newtonian gravity fluctuations. Could be done using (semi)analytical approach, or maybe purely numerical simulations.

• Wiener filter application (Jan/Michael)
  • Ran the old wiener filtering code on the new data.
  • There are ideas about related analyses, eg estimating the body waves by filtering 4850 with surface stations. Time scale, not sure, depends on what new things we want to add.

• Teleseismic EQs and near-surface scattering (Daniel, Victor)
  • Conference in April, Daniel would like to show some preliminary results then, turn into paper thereafter
  • Gary: with Ross working on something related, may be of relevance. Used 2015 data with events identified, ran it through a cross-correlation routine, splitting the array into subarrays to stack them better. Lots of measurements of wave speeds across the array, mostly from mining explosions. Might be able to pull out scattering information.

• Time-variable velocity changes (Victor, not started yet)

• Very low frequency harmonics (Ross)

• 1D velocity model (Daniel, Ross) - could be included in the summary paper or support the parameter estimation paper.

- Data analysis updates

• Data format: Gary will ask PASSCAL if they have already posted the data on IRIS. Should be proprietary data for another year.
• Vuk: received disk from Gary. Should be starting the conversion to frames soon.
• Ross' AGU presentation
  • Ross: station 800 had problems, sensor recentering
  • Pat: bad sensor, was replaced in April 2016, hopefully was fixed afterwards
  • Ross: data dominated by tides, even at 4850, very clean data.