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Homestake Meeting Minutes, 08/11/16

Attending:

Agenda: Andrew, Gary, Jan, Michael, Victor, Voon, Zhi, Vuk, Pat

• Tanner graduated - Congratulations!!!
  • Gary/Vuk: post his disertation on the wiki.
• Homestake Status
  • Daniel (email): I am on DQ shift this week, and while the data seems to be OK (with the known exceptions, RRDG, etc), it seems Tanner's DQ page is missing most of the links. Maybe a directory was moved around or permissions changed? In any case, the Caltech DQ page is still OK (same links and everything else).
  • Pat: transitioning from Tanner, will have to update the links.

• September trip to Homestake,
  • Sept 23-28
  • Gary, Daniel, Vuk (partly), Voon
    • Gary: giving a talk on Sep 20th and was planning on driving, so can't make it to Homestake before 09/23. Will have a pick up truck, so we need small car rental.
    • Victor: safety training for Voon?
    • Vuk: will check, but for surface work we should probably be OK.
    • Would be good for people flying in on 23rd
    • Daniel (email): still on board for the trip in September – just waiting to hear finalized dates before booking anything.
  • Tom should be OK throughout
  • Preparatory work: RR, contact private owners
    • Gary: the week before, will call the private owners to schedule the times preferable during the weekend. Also will have to call the school - maybe do it during the week, do some outreach. Gary will contact the teacher.
    • Vuk will have to develop the workplan and will have to schedule RR maybe for Monday.
    • Gary: will have to go to the roof to take down the radio, sometime during the week. Last time Jamey used the one-person crane to install it. Schedule it for monday so that we have time to react on problems.

• Data analysis
  • Levi (email): Tanner, Pat, and I met on Wednesday of last week to go over Tanner's parameter estimation routine. He mentioned that it was available on the SVN, but I haven't been able to access it. Either I am having troubles with SVN update, which would be unsurprising) or I need to checkout something which I don't have the name for. Anyway, I will talk to Pat about this to see if he is having any issues.
  • Michael/Jan pdf
    • Michael: initially did the analysis with 4 stations and got 50x suppression at 0.2 Hz, with some residual structure left over. Now trying to repeat it with the larger array: more channels and larger area. For coherence, using all stations including surface and far-away ones.
    • Improved to 100x subtraction at 0.2 Hz, no left-over structure in the residual. Using only sub-surface stations for the filter, adding the surface stations did not make much difference. Some excess noise was included at low frequencies - not sure why, in principle the filter should not get worse if you include more data (but in practice, numerical issues could cause a difference).
    • At 1 Hz still have 5-10x subtraction, and higher frequencies less suppression (2-3x), affected by local disturbances. Might be able to improve at high frequencies. Have 1.3 Hz and its harmonics which are not plane waves.
  • Zhi Li 113442_deep.pdf, 113442_surface.pdf, 113522_deep.pdf, 113522_surface.pdf
    • Study of an EQ in Japan, looking at the structure of scattering. Looking at the direction of the incoming wave at different depths. Doing the fk analysis at a specific frequency at the first arrival (P-waves) and then 40 seconds later (well before the surface waves arrive). Using the vertical component of the wave, plotting the horizontal directionality (slowness). Divided the stations into deep (4850+4100) and shallow ones (surface + 300). Using 20sec of data for Fourier transform. Direction near vertical, ellipses peak near the origin.
    • Zhi: Strong difference between deep and surface stations suggests that the shallow structure modifies the wave.
    • Victor: think that the deep plots are stretched by the geometry of the stations.
    • Jan: there is a strong local peak at 1.3 Hz. Why this frequency?
    • Zhi: searching 1.2-1.4 Hz band and choosing the highest signal within this band.
    • Victor: during the EQ, the signals is orders of magnitude above the noise.
    • Zhi: for future, will look at how much station geometry matters, look at the incident angle