Next: 41.4 SEED response to GSE, Up: 41. Instrument response Previous: 41.2 Examples of main response Contents Index
SEISAN can directly read SEED responses, which is poles and zeros,
given as velocity response and transfer function types A (Laplace
Transform in Rad/sec) and B (Analogue in 1/sec). Storage of response
in one of these is the most common. The resp files can be created
with rdseed from a full or dataless SEED volume
(rdseed -R -f seed_volume). RDSEED creates files with the
pattern RESP.NC.STAT.LC.CHC, where NC=network code, STAT=station code,
LC=location code (not used by SEISAN) and CHC=channel code. The resp
files need to be stored in the CAL directory and SEISAN will find
the correct file.
The RESP filename must match the waveform data, so if the
waveform data does not include network code and location code, then filename must be e.g.: RESP..BER..BHZ
So if the location code in the waveform data is '–' then
the RESP filename must include the '–', like e.g.: RESP.NO.BER.–.BHZ
And if the location code in the waveform data is empty ' ' then
the RESP filename must be like:RESP.DK.BSD..BHZ
If there are many files to change, program CHANGE_RESP_NAME can be used:
- make a dirf of RESP files that all require the same change to location and network
- length of station name is unimportant
- questions of changing/adding location and/or network codes, to see codes, plot with MULPLT
- if file has one'.' for code, it will be replaced by '..', also when no change is indicated
The resp file can contain response information from several time intervals. SEISAN uses the date and time of the waveform data to find the corresponding instrument response.
SEED response files are given in stages, for example seismometer, digitizer and FIR filters are stored as individual stages. The overall response is made by combining all the stages. SEISAN uses the following blockets from the SEED resp file (for more details see IRIS Consortium (1993)):
B052F22 - start date
B052F23 - end date
B053F03 - transfer function type, A=Laplace Transform (Rad/sec), B=Analog (1/sec)
B053F07 - A0 normalization factor (A0 is checked against poles and zeros at normalization frequency and changed if not correct). The product of poles and zeros at the normalization frequency and A0 gives 1.
B053F08 - Normalization frequency
B053F10-13 - zeros, if transfer function type is B, normalization factor A0 is changed to (A0)/(2 pi) for each zero
B053F15-18 - poles, if transfer function type is B, normalization factor A0 is changed to (A0)*(2 pi) for each pole
B058F04 - gain
The overall gain factor is given by the product of normalization factors and gain factors from all stages. One zero is added to convert to displacement response. It is assumed that input units are V/m and output units are counts, no checks are done on input and output units.