Summary
If the sample rate recorded in the miniSEED fixed header and the sample rate estimated from the high-frequency rolloff of the metadata amplitude-frequency response curve disagree by more than 15%, sample_rate_resp is 1 (TRUE). Otherwise it is 0 (FALSE).
Uses
This metric checks whether a channel’s instrument response correctly describes its sample rate. FIR filtering produces a high-frequency corner near 0.85*Nyquist. Not only will sample_rate_resp catch responses that describe a different sample rate, but it will flag responses that omit FIR filter stages. An incorrect response is easily fixed by correcting and resubmitting the errant metadata.
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? | High Gain, Low Gain, Accelerometer, Gravimeter, Geophone
Algorithm
- Request 24 hours of data for a single N.S.L.C.
- Request 100 frequency samples per decade between the response normalization frequency and the (miniSEED sample rate * 10)
- Calculate the percent amplitude change (dAmp) between frequencies
- For each dAmp
- if dAmp <= -10, corner frequency = frequency of dAmp
- resp sample rate = 2*corner frequency
value = '1': abs(resp sample rate - mseed sample rate) < (mseed_rate*0.15) | '0'
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Metric Values Returned
value – ‘1’ (TRUE) if miniSEED and response-estimated sample rates disagree by more than 15%; ‘0’ (FALSE)otherwise
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
Because this metric estimates sample rate from a channel’s amplitude-frequency response, it is not valid to run it on channels with nonlinear instrumentation whose responses described solely by polynomials.
