Homestake Meeting Minutes, 01/28/2016
Attending: Gary, Ross, Daniel, Levi, Vuk, Tanner, Pat, Michael
Homestake wiki: https://zzz.physics.umn.edu/groups/homestake/home
1) Homestake array
- status of stations
Gary: only one problem, the WTP, which had a power problem. Either the battery or the solar panel not getting enough exposure. Will have to address it when we go there next time.
Gary: have to deal with the balers, the first ones may have to fill up underground B4850 (noisy station, near the fan) in April. Also stand alone stations.
Data flow seems to be flawless. Frames copied to Caltech up to Dec 2015, will send January frames in the next few days. Pat will take over the data flow management.
- planning next visit
Mid April: Daniel can't make late April, Pat can't make the first week of April. The window between April 10-20 should work.Terry might be able to join too.
2) data analysis updates
Levi presented the UPDATED Analysis of Depth-dependent Shear Waves PowerPoint
. Found information about rock composition at Homestake, combined with the information on hardness of different minerals, and computed an average hardness of rock in different locations at Homestake. Appears Homestake falls in the “generic rock” category. Gary suggests to repeat the same with P and S speeds, which would give us the baseline speed for unfractured rock. Combined with velocity measurements, we could extract information about fracturing in the rock. Gary will work with Levi on this.
Gary: use explosions at 4850 to estimate the free-surface amplifications, we should be able to measure it directly.
Gary/Ross: processing the reflection line experiment at 2000 level, seeing scattered waves off of mine works. Not clear if the reflection off of the free surface can be observed. Have measurements of shear wave velocities at this level, comparing it now with the geology information. Complementary to the Roggenthen paper linked above.
Gary also working on the timing information with the weight drop experiment (recall the timing system failed). Measuring cross correlations and trying to estimate the event times from there. Using our array time as a reference. Messy bookkeeping problem.
Measured peak velocities generated by explosions at Homestake in Dec. Will look at the amplitude fall-off with distance from explosion.