SAGE Facility MUSTANG metrics Web Service Documentation

Displays the RMS variance of trace amplitudes within a 24-hour window.

Daily RMS variance reflects the dynamic variation of time series. It reveals time periods where amplitude variation was unusually large or small. RMS values that abruptly drop to zero, give or take, can indicate a “broken” channel or sensor. Large, short-lived RMS values can indicate an event, calibration, mass recentering or other large transient noise signal. Longer-lived changes can indicate the beginning of instrument malfunction or a new source of site noise. For mass position, large RMS could indicate drift.

Traces – one N.S.L.C (Network.Station.Location.Channel) per measurement
Window – 24 hours starting at 00:00:00 UTC
Data Source – IRIS miniSEED archive or IRIS PH5 archive

SEED Channel Types – ?H?, ?L?, ?N?, ?G?, ?P?, VM? | High Gain, Low Gain, Accelerometer, Gravimeter, Geophone, Mass Channels

• Request 24 hours of time series data for a single N.S.L.C.
• Calculate the RMS variance of all samples in the requested data:
  

  For i=1,N samples in the time series x:
      mean = { sum[x(i)] / N }
      RMSvariance = sqrt{ sum[ (x(i) – mean) ^2 ] / (N) }
  

value – RMS variance of the time series in counts
target – the trace analyzed, labeled as N.S.L.C.Q (Network.Station.Location.Channel.Quality)
start – beginning of the data day requested (00:00:00 UTC)
end – end of the data day requested (truncated as 23:59:59 UTC)
lddate – date/time the measurement was made and loaded into the MUSTANG database (UTC)

RMS variance is identical to standard deviation. Unlike the RMS amplitude, the RMS variance omits the DC component from the signal, making it possible to compare RMS values across traces with differing DC amplitudes.

Instrument response has not been removed.