Homestake Meeting Minutes, 07/23/15

Attending: Tanner, Pat, Victor, Gary, Daniel

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

Our agenda:

1) Homestake array status (Gary, Tanner, Daniel, Pat)

• Gary: found a few timing problems on 4100/4850, talked to Jamey and he took care of it. Also found the right procedure for recentering the stations through Antelope and centered two stations. E2000 is still throwing big tilt events. WTP has lots of data gaps, probably due to weather issues since the connection is marginal.
• Tanner: we still have the mast, and Tom wrote up a JHA for putting it up, if you feel ambitious!
• Gary: one option is to try the new directional antennas that we tried at LHS. They have a slightly higher gain than the Yagis and it may help. We will want to swap out the baler at WTP too because of the data gaps.
• Tanner: did everyone see the e-mail from Jamey about putting a phone, desk, and computer at our C4850 site? Not sure if we should do this, should wait until Vuk gets back to make a decision.
• Gary: yes, we don't want to increase foot traffic near our sites.

2) Next Homestake trip

• Gary: will arrive day before Labor Day and get things organized. Will spend first few days checking underground sites and surface sites. Want to get a new pad poured at E2000 site. Lee Liberty and his crew will arrive on Sept. 12. That weekend we will do surface shooting. Problem will be that if we do this over the weekend, we won't be able to do shooting on the lab property, which will be useful for calibrating how much of a signal we are seeing from the experiment. Sept. 15-24 will be underground shooting experiments.
• Tanner: what is the plan for E2000? Pour a bigger pad of concrete, how to preserve alignment?
• Gary: thinking of chipping away concrete in about 2'x2' square, building a form and pouring a new pad, then using one of the leftover tiles we have on top of that pad. I have a device that I think will be useful for preserving our alignment. Will use this device for alignment in the active source experiments, too.

3) data analysis

• Tanner: no update from UMN, busy with other things.
• Gary: working on some tools for doing particle motion analysis quantitatively. Takes seismograms and plots vector motion in 3D so you can visualize the particle motion. Needs a GUI so you can specify certain parameters, but it's difficult to do.
• Gary: what's more important to do is to take the data and try to find a model for the particle motion. Using multi-wavelet method to get best-fit of particle motion ellipse at a given time step and in a given frequency band. This is a useful tool for anisotropy, helps to quantify the actual particle motion in terms of a major and minor axis and look at the frequency dependence. Can measure orientation of the ellipse relative to direction of wave propagation; will tell us how much particle motion deviates from simple models. Can also try to quantify shear wave splitting.
• Daniel: have been working with Victor to take waveforms from a given event and find the optimal waveform to describe it. So far we are just using time delays, nothing fancy with anisotropy or reflection, but it's working well so far.
• Gary: is this just cross-correlation?
• Daniel: taking the waveforms from the onset t-arrival and doing an inversion that would account for them and for free surface reflections. We are seeing a very strong effect from free surface reflections, it might be very useful to include this in the radiometry code as well.

Next call August 6.