Homestake Data Analysis Workshop, 10/23-25, 2015

Agenda:

{{groups:homestake:workshop_umn201510_vuknotes.pdf|Vuk's notes}}

Friday, 10/23
  - Gravitational Waves: goals, instrumentation, role of seismic noise: {{groups:homestake:201510_gw_seismic.pdf|Vuk's slides}}, {{groups:homestake:analysis:directional_analysis_v2.pdf|Radiometer Note}}
  - Seismic Waves Primer (Gary)
    - P and S body waves in isotropic media, 
    - Rayleigh and Love waves, 
    - anisotropic media basics (velocity dependence on direction, shear wave splitting, and particle motions in an isotropic medium), 
    - free surface interaction in isotropic and anistropic media. 
  - instrument calibration, try to get it going during the workshop
  - Composition of the seismic noise: radiometer and other algorithms, understanding the Rayleigh waves (amplitude dependence on depth, P-vs-S contributions) - Vuk, Tanner, Levi

 
Saturday, 10/24
  - Goals with Homestake data (Victor): {{groups:homestake:greensfunction_victor.pdf|slides}} and {{groups:homestake:tsai_gji2010.pdf|paper}}
  - Brief overview from Gary: {{groups:homestake:msp2015workshop_pavlis.pdf|slides}}
  - Gary has some analysis code under development to show.  These are tools to visualize and measure three-component particle motions.
  - Overview of the active source data and any preliminary results (Gary/Ross)
  - What do we know about velocity (vs depth, vs direction) - this is linked to your active source study
  - Work on earthquakes (Daniel)
  - noise cross correlations (Daniel)
  - Event catalog  (Gary)
  - Extending the life of the array?
  - papers?

Sunday, 10/25
  - Wiener filter study - this is pursued by Michael Caughlin and Jan Harms, and neither will be present. Maybe we can ask them to connect remotely - {{groups:homestake:presentation_wiener.pdf|pdf slides}}
  - Coupling of solar wind modes into Earth modes (Ross):  {{groups:homestake:workshop_hum_talk_mod.pdf|pdf slides}}
  - glitch-finding algorithms

===== Data Analysis Projects =====

  - Solar wind modes (Ross, Gary)
    - measure lines in the spectra at low frequencies, 40-400 uHz, using multi-taper techniques
    - could potentially benefit from tilt-meters or magnetometers
    - depending on the absolute displacements, possibly could do this with GPS stations.
    - could also try cross-correlations between pairs of detectors
  - Deep EQ in Japan (Daniel, Victor)
    - Estimate incident and reflected waves, resolve them as they propagate through the array.
    - Deep source, does not suffer from surface effects. Can get a cleaner incident signal at deeper stations. 
  - Cross-correlations (Daniel, Victor)
    - cross-correlation between two stations is related to the Green's function relating the two stations, under the assumptions of isotropic source distribution and equipartition of energy.
    - extract the dependence of Rayleigh wave speed on frequency, which gives the dependence of shear wave speed on depth.
    - may be able to measure body waves directly with underground stations?
    - Could potentially detect the presence of Love waves. 
    - Attempt to compare the noise correlation functions (pseudo-Green's functions) from different periods of time to see if we can resolve temporal or seasonal differences in the structure (i.e.: a difference in fluid content or snowpack weight between summer and winter). 
    - test various pre-processing techniques to maximize signal recovery. This may be of relevance for radiometer signal pre-processing too.
    - How does this extend to isotropic GW background? Can you measure the speed of gravitational waves? (Vuk, ...)
  - Visualization of the motion (Gary)
    - identify polarization of the waves. At high frequencies expect deviations from the standard theory due to anisotropy. At low frequencies the standard theory probably fits data better.
    - Can you apply these visualization techniques to seismic noise in very narrow bands? Do you see the retrograde/prograde motion? Do you see Love waves?
  - Active source experiments (Ross, Gary)
    - Measure the speed at different locations on the surface and along the drifts where the measurements were done
    - try to extract average speeds in other directions/locations using the active sources and the Homestake array instruments. Would need the absolute timing of the shots, which does not exist but could be estimated.
  - Wiener filter (Michael, Jan)
    - how well does the subtraction work at different depth, different frequencies, different filter lengths
    - how do we determine the optimal array design? Test performance of the filtering after dropping some of the stations
    - Question: is it possible to use the spatial patterns of signal coherence (or some other misfit metric) to map regions of higher scattering or anisotropy, and/or to determine a weighting scheme for a radiometer or beamforming code?
  - Related to Wiener: how do we measure correlations in an inhomogeneous seismic field? That is, how do we measure/identify local sources, local scattering etc?
    - Use the deep EQ in Japan to estimate the incident and reflected waves, subtract them from data and the residual should carry information about the local scattering...
  - Event Catalog (Gary)
    - Continue to identify and catalog events observed by the Homestake array
    - correlate them with USGS database
  - Glitch-finding algorithms (related to the Event Catalog above)
    - Apply Omicron to the Homestake data (Michael)
      - look at events on the time-scale of 1 sec, including local (mine) events
    - Try to apply STAMP to an example EQ other events on the time-scale of 100sec (Tanner, Pat?)
      - If the results are interesting for geo, potentially consider other applications
  - Radiometer (Tanner, Pat, Levi, Vuk)
    - correct the Rayleigh model: double exponential, new speed estimates etc
    - for speeds: could start with the preliminary estimates from Gary: v_s = 3300-3900 m/s, v_p = 5700 m/s
    - for speeds: in the long terms would like to use the estimate of v_s(depth), estimated as a power law. This would then give us all exponentials for Rayleigh and Love waves. 
    - modify the code to use larger frequency bands, windowing, etc
    - develop a tool for Love waves as well (single exponential).
    - compare to existing directional tools