C.2 GSE response format

Below is an example of a GSE response file generated by RESP for the same parameters as used for the SEISAN file above. The GSE response format is rather complex, and can contain parts that will not be understood by SEISAN.

Below follows an example of the GSE response using FAP. The first line gives station and sensor type. The numbers following are gain in nm/c (0.15) at reference period (1. seconds), sample rate (20) and date. The following line (FAP2) gives a gain factor (1.) and the output units (V for Volts). Finally follows the frequency, gain and phase triplets.

CAL2 KBS   B Z      STS-1    0.15E+00      1.   20.00000 2003/ 1/ 1  0: 0
FAP2  1 V                60
    0.00500  0.48047733E-02  138
    0.00590  0.57846815E-02  130
    0.00700  0.69361408E-02  123
    0.00830  0.82667302E-02  117
    0.00980  0.97841555E-02  113
    0.01200  0.11995634E-01  108
    0.01400  0.14000172E-01  106
   60.00000  0.59999992E+02   90
   71.00000  0.70999992E+02   90
   85.00000  0.84999992E+02   90
  100.00000  0.99999985E+02   90

In the poles and zero representation, the file looks like:

CAL2 KBS   B Z      STS-1    0.15E+00      1.   20.00000 2003/ 1/ 1  0: 0                       
PAZ2  1 V  0.26000000E-05                 2   3 Laplace transform                               
 -0.12217305E-01  0.12464144E-01
 -0.12217305E-01 -0.12464144E-01
  0.00000000E+00  0.00000000E+00
  0.00000000E+00  0.00000000E+00
  0.00000000E+00  0.00000000E+00
DIG2  2  0.41900000E+06    20.00000 quanterra     

The first line is the same as before. The PAZ2 lines has the following meaning: Normalization constant of seismometer and filter (0.26e-5), number of poles and zeroes (2 and 3), and the type of response (Laplace transform). The DIG2 line has the gain of amplifier and AD converter combined (0.419e6 c/V) and sample rate.

In the simplest case, the response is given by the PAZ and a scaling factor. It is common (like in SEED) to have two scaling constants, one that normalizes the PAZ to amplitude 1 at a calibration period, and another constant that gives the amplitudes in the physical units. This is NOT the case with the GSE2 format. The GSE2 response for PAZ normally contains at least two parts, the CAL2 line and a PAZ2 line. The scaling factor should scale the PAZ to output/input units, NOT normalize. In the CAL2 line, the system sensitivity at a calibration period is given in units input/output, but is generally not needed. The total response is given by the PAZ, multiplied with the PAZ2 scaling factor, or the product of several stages.

This is how SEISAN reads the response, however, if it finds that the PAZ2 gives normalized values at the calibration period, the response is multiplied with the sensitivity given in the CAL2 line (this is done because such GSE files have been seen).

FIR filters can be specified in GSE as an additional stage and can be written out by the RESP program. An example is given below. The FIR filter coefficients are required to completely describe the instrumentation. However, they are not used in SEISAN.

FIR2 3 0.10E+01 3 0.030 A 180
0.18067658E-06 0.88848173E-06 0.24195760E-05  0.37699938E-05 0.32037496E-06
 -0.18581748E-04 -0.69605186E-04 -0.16990304E-03 -0.32499805E-03 -0.51408820E-03
 -0.68242848E-03 -0.75194239E-03 -0.65436028E-03 -0.37627667E-03  0.94138085E-05
0.35409257E-03 0.49653835E-03 0.35531260E-03 -0.29224902E-05 -0.37382543E-03

Peter Voss : Tue Jun 8 13:38:42 UTC 2021