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 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 ):
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.