41.3 SEED response

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 [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.