groups:homestake:meetings:20140626 [School of Physics and Astronomy Wiki]

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Homestake meeting minutes, 06/26/14

Attending: Tanner, Vuk, Victor, Noah, Gwynne, Shivaraj

Homestake wiki: https://zzz.physics.umn.edu/groups/homestake/home

Our agenda:

1) Homestake update (Vuk)

Vuk: planning a visit to Homestake on 7/28-29, along with Victor. Goal to finalize the locations, decide where the seismometers will be located, where the batteries should be placed, finalize the GPS distribution system (including fiber choice etc). Hope to make orders for fibers and GPS system soon after the visit.

2) UMN test setup (Tanner)

Tanner: New optical transmitters and receivers from Liteway, sending both 1pps and NMEA signals over a single fiber. Reduced power requirements. Operated a single receiver off of a battery, along with the digitizer, baler, and seismometer - lasted 5 days with 55 amp-hour battery. So 20 batteries like this would allow us to run for 3 months.

Vuk: As Tanner mentioned, at Homestake we should have lower seismic noise and therefore lower power consumption. On the other hand, the GPS modules will likely have to use lasers, which may require more power than the modules we used (which use LEDs). 

Tanner: next week will play with the daq, try to stream data.

3) Analysis of existing data

Noah: trying to understand whether aliasing can be reduced by integrating over different frequencies or over longer time periods. Posted a  {{groups:homestake:meetings:temporarypowerpoint.pdf|report}}. Observe that the checkerboard pattern coalesces with averaging, but the results in general are not as good as in cases where there is no aliasing.

Victor: try to average over longer time periods, maybe of order 1 day.

Vuk: try to average instead of integrating over different frequencies/times.

Vuk updated the directional analysis note: {{groups:homestake:analysis:directional_analysis_v2.pdf|pdf}}. The note now includes the calculation for Rayleigh waves, following the discussion between Victor, Eric, and Vuk at Caltech several days ago. Results are similar to P-waves, with the distinction that there is an exponentially decaying factor (with depth) and a different coupling of the wave to the seismometers' channels. 

Vuk/Victor: plan to have multiple tools that we could use to look at the data. Rayleigh waves will dominate at least the shallower part of the array at Homestake, so it will be useful to apply such a tool to understand what component of the data could be explained with the Rayleigh model. 

Next meeting: 7/24.
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