Homestake Meeting Minutes, 07/27/17

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

Agenda:

  * Next Meeting: Aug 24.
  * Data analysis topics
    * Data corrections, frame production (Gary/Daniel/Pat)
      * Pat: Frames ready at Caltech. 
      * Daniel: Some timing hiccups, especially when a station is reset, timing off by 1/4 of a second. Have to chase it further, may be ignorable.  Doesn't happen often. We could flag the times/stations when this happens. (See also below)
      * Don't know if IRIS updated the data yet, should check with Gary...
    * Event catalog (Gary/Ross)
    * Radiometer updates (Pat, Andrew)
    * Parameter estimation for Rayleigh and Love (Pat) - {{:groups:homestake:meetings:rwave_eigenfunctions_presentation.pdf|pdf}}
      * Velocity estimate is close to the local phase velocity, estimated using local displacements as a function of depth.
      * Homogeneous half-space is not a good approximation, don't get good fits to the depth data.
      * H/V ~ 1.3 - Victor: this is normal/common.
    * Teleseismic events and Wiener filtering (Daniel, Michael)
      * Vuk: making progress, will try to present at the next meeting.
    * Very-long-periods (Ross) - {{:groups:homestake:meetings:Caton_20170726_longperiods.pdf|pdf}}, {{:groups:homestake:meetings:Caton_20170726_longperiods.pptx|pptx}}
      * Putting a paper together. Large section written up. Expect to circulate it in a month or so.
      * Next try to remove tides alone, see how that affects the data.
    * Velocity from noise correlations (Daniel): {{:groups:homestake:meetings:bowden_20170725.pdf|pdf}}
      * see timing glitches at some times.
      * Pat: seems to be related to bad timing, maybe due to network problems. 
      * Ross: may be an issue with the 800 station, had a large number of mass re-centerings. 
      * Daniel: Also see slow drifts in RRDG, know that we lost the clock in this station towards the end of the run.
      * Find time-shift between two stations to match the waveforms, this gives the group velocity. Do it for each station pair individually, works well for some cases and not for others.
        * Similar to Pat's analysis, but using the noise instead of transients.
      * Concern regarding uncertainty for station pairs that are close in horizontal plane. Maybe not seeing Rayleigh waves, will follow up on this.
      * Results in velocity estimates and eigenfunction profiles. Can compare to Pat's approach.
      * Vuk: Maybe we can combine these measurements with Pat's and do model selection for eigenfunctions. 
        * Victor: there are many models out there, may have to constrain them a bit before launching into it.
      * Gary: active data may also constrain these, some of the models are definitely not supported by the data.
      * Daniel, Ross, Gary, Pat: will try to pull together all velocity measurements to start making comparisons. Pat will send the link again.

  * Papers
    * Homestake Array Summary paper: {{:groups:homestake:meetings:paper_20170725.pdf|pdf}}
      * Leads: Vuk, Gary, Victor
      * target: Seism. Research Lett., 6000 words, 10 figures.
      * Gary almost done with updates in the paper. 
      * Vuk will send it for internal LIGO review when Gary is done. No objections to this plan.

    * Active excitation overview paper
      * Leads: Gary, Ross
      * Others: Victor, Daniel,…
      * Will discuss at the next call.

    * Surface Active Excitation
      * Leads: Victor, Boise
      * Others: Gary, Ross
      * Victor talked to Lee - they are planning a more general paper on H/V etc, will include the landstreamer data in it. Timeline: next couple of months to write it up. Happy to have input from us.
      * Vuk: it seems this would be decoupled from any papers we want to pursue. 
      * Gary/Victor: Agree.
      * Vuk: let's invite them to give us a presentation in a couple of months, when they are ready.

    * 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
      * Novel, but maybe insufficient for a publication. Could use the eigenfunction measurement for Rayleigh and assume something about Rayleigh field to make preliminary estimates of the Newtonian noise. 

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

    * Wiener filter application
      * Leads: Jan, Michael    
      * Aim for late August.

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

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

    * Very low frequency harmonics (Ross)