Homestake Meeting Minutes, 01/18/18

Attending: Ross, Gary, Vuk, Daniel, Andrew, Pat, Michael

Agenda:

• Next Meeting: Feb 16?
• Data analysis topics
  • Data corrections, frame production (Gary/Daniel/Pat)
  • Event catalog (Gary/Ross)
  • Radiometer updates (Pat, Andrew) radiometer_update_2.pdf
    • Ran radiometer and simple phase beam-forming on 1.4 Hz transient feature. Observed the two methods to agree well. Expect it to be human-generated, seems to be aligned with local mining work, direction of Terry Peak.
    • At 1.5 Hz expect the wavelength ~3km, should see them underground as well, but we don't seem to. Is it possible that eigenfunctions are such that the amplitude is significantly lower?
    • Ross: Could compare the blast events from this mine, and compare the waveforms on the surface and deep underground.
    • Gary: good idea.
    • Daniel: velocity of 2.8 km/s, implies this is surface wave…
    • Vuk: could also look at distant stations to check locality of the effect.
    • Gary: could follow up with Jaret.
    • Pat: will try to add deep stations.
  • Parameter estimation for Rayleigh and Love (Pat)
  • Teleseismic events and Wiener filtering (Daniel, Michael)
  • Very-long-periods (Ross)
  • Velocity from noise correlations (Daniel)
    • Model selection?
  • Pull together all velocity measurements to start making comparisons (all)

• Papers
  • Homestake Array Summary paper:
    • Leads: Vuk, Gary, Victor
    • Submitted to Seism. Research Lett.

• Active excitation overview paper
  • Leads: Gary, Ross
  • Others: Victor, Daniel,…
  • Draft of the paper exists, as a report for IRIS. Gary will be adopting it to a publication. Don't have a particular date in mind.
    • Gary is working on this, building figures and adding text. Could add a “live 3D” interactive figure, could add it to a paper, as a supplement.

• Surface Active Excitation
  • Leads: Victor, Boise
  • Others: Gary, Ross
  • Plan to invite the Boise group to give us a presentation in Sep or Oct 2017, when they are ready with their paper.

• 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
  • Latest version: wiener_v4.pdf.
    • Addressing comments from previous meetings, added an appendix including 0.1 Hz (which does not show bi-modality) and 0.4 Hz (which is more complex) - both as expected. Modified the coherence-vs-amplitude plot, including both Homestake and Sweetwater arrays.
    • Trying to correlate with wave heights and dominant period of the wave. Made a movie trying to depict this - work in progress. Observe some correlation, have to study more. The secondary microseism comes from deeper water activity, while the primary comes from the interactions with the coast. In the first third of the movie, the ocean activity is limited to the southern hemisphere, which would generate body waves that we see during those times. Then, the northern ocean pick up in activity, and we can see the surface waves from this (and increased seismic amplitudes).
    • Trying to find relevant metrics to depict this effect.
    • Daniel/Gary: not sure if this will be a part of the paper, there is still a lot to do.
    • Gary: the appendix could be turned into a supplement.
    • Michael: maybe a supplement could be used to show the movie.
    • Michael: Will talk to Jan about whether to include this in the paper or not. Guess that final fixes to the paper should not take long, expect in a couple of weeks to finalize the modifications. Can work with Victor and Daniel in person to speed up the process.
  • Daniel's slides: 2018-01-18_bowden.pdf.
    • Similar measurements to what Michael is doing, coherence on ambient noise. Get the same conclusions as Michael. Used also further stations as well.
    • Michael: would a plot of this type help relate to the geophysics community?
    • Daniel: Maybe, will get back to this. Will discuss with Michael/Jan.
• Teleseismic EQs and near-surface scattering
  • Leads: Daniel, Victor

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

• Very low frequency harmonics (Ross)
• 3D PDF of Homestake geometry - draft for active source experiment paper homestakeexperiment.pdf