Homestake meeting minutes, 05/28/15

Attending: Vuk, Levi, Tanner, Victor, Daniel, Gwynne, Gary, Pat

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

Our agenda:

• Homestake status (Gary, Tanner, Daniel, Pat):
  • Yates station: there was water in the dog house which ruined the power box. Replaced the power box, working well now. Likely that the water came in through a vent, sealed it now. Did not do the same fix on other dog houses.
  • Installed 3 far stations. The main concern is with the Deadwood site is that they hit the water level, so made a bit of a trench around it.
  • 1700-1: after some troubleshooting, took some hardware to the surface, tested some more. Eventually found a loose pin in a connector - fixed it, and now working.
  • 2000-A: Q330 found in a strange state. Rebooted it and now working again. PASSCAL did not know about this failure more. Gary thinks it is the firmware, will have to watch how things behave over time. Data is saved on the baler, but did not harvest it.
  • 2000-E: observed that the grout around the granite tile was drying and flaking off. The tile is firmly attached to the concrete, but the concrete is old and crumbling. The site is also wet. Not sure if the tilt events are related to the grout or to the concrete. We'd have to make a significant change to this station (probably pour a new piece of concrete), so decided to leave it for later. Gary: the tilt events are rather low-frequency events, so we should be able to filter them away. Fixing this will require 2 underground trips.
  • Rhyolite Ridge and Highschool sites also installed. RR working fine. HS has a radio communicating with the computer in the building, but the interference is significant and the connection is not very good. Might be able to improve it by directing the two antennae to each other better, maybe 1-2 hours of work in the next trip. Gary: there is another option using low-frequency (900 MHz) antennae, avoiding the interference. PASSCAL has some of these, could consider installing in the next trip. Gary will pursue it.
  • Gary: still cannot access the HS computer, which we should be able to do via VPN. Will try to get in touch with the IT person there, but at the moment don't have access the computer or the radio remotely. So at the moment the HS is acting like a stand-alone station.
  • Two of the far stations have 2 batteries each, should check on them in the fall to make sure they are working well.
  • So, remaining issues: 2000-E tilt events, HS connection problem.

• Next Homestake trip (August/September)
  • planning for active excitations: Gary had a meeting with the city manager, who was 100% supportive. They asked us to finalize where we want to do this in town, and when (dates). Similarly for the Sanford Lab property.
  • Victor: could use the preliminary locations from the proposal?
  • Gary: agrees. Start from WTP, connect with Yates, continue via Summit ave to the school. Then should do some cross lines. Another option is the road toward Oro Hondo.
  • Vuk: try to get Lee on the next call.
  • Lee's constraint: end of august at the earliest. Gary is on sabbatical, so could be there for the whole exercise. Probably need a week, and at least one more person in addition to Gary. Daniel ok with this time period. Tanner ok in September. Pat ok in early September.

• data analysis
  • calibration: Daniel - we have the nominal calibration, they are on SVN. Could produce our own calibration files for each seismometer. Gary: this is a standard procedure for this, injecting a set of signals. Started some (phase 1) last week, but did not finish it. Won't be able to do this at the remote sites. Get full frequency-dependent calibration curve. Application to appropriately scale the data are typically in frequency domain.
  • coordinates: Gary will provide the coordinates for the surface sites in Kathy's system. Once we retrieve the data from balers, position coordinates should improve. Currently, precision is a few meters.
  • Daniel/Victor: observe the initial part of the EQ arrival, should have less distortion than the surface. Do source imaging. Also want to look at the reflections off of the surface. Also interested in the radiometry code and comparison with other beam forming techniques. Most of this would be in time domain with transients, sometimes work in frequency domain but convert back in time.
  • Gary: plans related to the particle motion video circulated before. Interested in the anisotropy behavior. Trying to use and upgrade older tools based on multi-taper spectral method and wavelets, designed to optimize the time-frequency trade-off (measure narrow band, but with as short segments as possible). Look at the particle motions at different frequencies. Test the decay rates with depth as a function of frequency. Expect the rock to be anisotropic, want to test theory for this kind of setting. Also, the active source data could give us direct measurements of anisotropy, maybe able to convert this into a 3D tomography model of the medium. Expect to have several thousand shots from the active source, recorded by all our stations - large amount of data, will take much effort to analyze it.
  • Vuk: aim to extract modal and directional content from the data using the radiometer and other beamforming techniques, in the 0.1-10 Hz. Overlaps with both of the above directions.
  • data analysis workshop: probably 2-3 weeks after the active source experiment, maybe mid/late September. Revisit in 2 weeks.
  • when do we harvest data from balers? Surface balers will fill up in about 1 year, underground ones in 1.5 years. Some of the surface sites are not accessible in the winter. August/Sep is when we should do this on at least some of the surface stations.
  • Authorship policy: those involved in the construction of the array (Daniel, Victor, Pat, Tanner, Gary, and Vuk) will be authors on all papers published with this data. Others that help with specific analysis projects could be authors on those papers, but not on all the other papers.