The folders contain monthly overviews of the ground acceleration power spectral density PSD
 
The seismic channels are checked for completeness and, if there are at least
20 min of data, we compute a hourly PSD as follows:
- take the raw data and split the 3600s time window into 200s time windows
  with 100s overlap (i.e. 35 time windows)
- compute the PSD using Welch's method
- interpolate the PSD onto a evenly spaced log10 frequency axis
- divide the PSD by the squared acceleration system response
  (i.e. convert the raw data PSD (units in counts^2/Hz) into 
   ground acceleration PSD (units of m^2/s^4/Hz))
- the hourly PSDs are stored in a temporary archive to be used to generate the
  monthy overview plots


Once per day the monthly PSD plots are updated as follows:
- read all hourly acceleration PSDs for the respective month
- transform the units of the PSD in dB by using 10*log10(PDS)
- compute an average PSD from all hourly PSD and plot the average PSD curve
  and its associated axis in read color in the overviews
- compute the residual of each hourly PSD from the average PSD and display
  the residual color-coded from blue (values below the average PSD) to red
  (values above average PSD)

For infrasound channels we compute the atmospheric pressure power 
spectral density. The PSDs are in units of Pascal^2/Hz and
are displayed in dB (i.e.,10*log10(PSD))


Michael Roth 2024-08-08