Summary
This metric reports the average amplitude value in counts over a 24-hour window. This mean is one measure of the central tendency of the amplitudes that is calculated from every amplitude value present in the time series. The mean value itself may not occur as an amplitude value in the times series.
Uses
Like the median, the mean amplitude of a time series describes its static behavior. For a properly functioning instrument, it can echo a channel’s DC level and/or mass position. Sudden changes in mean can indicate partial loss of differential output, particularly if the RMS variance suddenly decreases simultaneously. Because the mean is sensitive to outliers, sudden changes can sometimes accompany the onset of strong asymmetric noise.
Data Analyzed
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
Algorithm
- Request 24 hours of data for a single N.S.L.C.
- Compute and report the average amplitude of time series:
For i=1,N samples in the time series x: mean = { sum[x(i)] / N}
Metric Values Returned
value – mean amplitude 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)
Notes
Instrument response has not been removed.
