41.2 Examples of main response files from seismometers and accelerometer

Example of a Güralp DM 24 digitizer with CMG-40-1 (1 Hz)

Digitizer:

The sensitivity of the digitizer is given to $3.197 \mu V/count$. The SEISAN gain is in counts/V so

SEISAN recording media gain =1000000/3.197 = 312793 count/V

Sensor:

Sensitivity is 2 X 1001 V/m/s =2002 V/m/s

Making response file with parameters

For calculating with parameters, it is assumed that the free period is 1.0 s and damping is 0.7. Using the resp program answering as follows

Output format: 0 Only testing
Type of sensor: 1 It is a seismometer
Seismometer period: 1.0
Seismometer damping: 0.7
Generator constant: 2002
Recording media gain: 312793
Amplifier gain: 0 No amplifier
Number of filters: enter No filter
File with poles and zeroes: enter We use parameters now
File with tabulated values: enter
File with measured values enter

Then the plot below comes up

Figure 41.1: Making response file with parameters.

Making response file with poles and zeros

The poles and zeroes velocity response in units of Hz is given as

Poles
-0.707 0.707
-0.707 -0.707
-62.4 135.4
-62.4 -135.4
-350.0 0.0
-75.0 0.0

Zeros
0.0 0.0
0.0 0.0

SEISAN units are radians/sec so poles and zero values are multiplied by $2\pi$.
The normalization constant is given as $585.8 10^{6}$. To convert to radian is done as follows

Normalization constant in radian = $585.8 10^{6} (2\pi)^{(number of poles-number of zeroes)} = 585.8 10^{6} (2\pi)^{4} = 9.12 10^{11}$.

SEISAN also uses displacement so one zero is added. The values are then

Poles
-4.442 4.442
-4.442 -4.442
-392.0 850.7
-392.0 -850.7
-2199.0 0.0
-475.0 0.0

Zeros
0.0 0.0
0.0 0.0
0.0 0.0

To get total constant (gain and normalization constant), we multiply by sensor gain and digitizer gain

Total normalization constant = $9.12 10^{11} x 2002 x 312793 = 5.71 10^{20}$

A SEISAN input file is then made

6 3 5.71e20 6 poles, 3 zeros and total gain constant
-4.442 4.442
-4.442 -4.442
-392.0 850.7
-392.0 -850.7
-2199.0 0.0
-475.0 0.0
0.0 0.0
0.0 0.0
0.0 0.0

The resp program now makes the SEISAN response file with this input as follows

Output format: 0 Only testing
Type of sensor: 0 Sensor response is in poles and zero file
Recording media gain: 1 Gain has been put into total gain constant
Amplifier gain: 0 No amplifier
Number of filters: enter No filter
File with poles and zeroes: resp.inp File with poles and zeros, can be any name
File with tabulated values: enter
File with measured values enter

Then the plot below comes up

Figure 41.2: Making response file with poles and zeros.

It is seen that the two ways of making the response file gives almost the same result, however using poles and zeroes is the most accurate, particularly for active sensors. In both cases no consideration was made for antialias filters which normally can be disregarded if a modern sharp filter.

Example of a Gurlp DM 24 digitizer with CMG-5T accelerometer

The digitizer is the same as before

Using parameter format, SEISAN currently requires the component name to start with A. According to international standards, the component code for an accelerometer should be something like ENZ so a parameter format cannot be used if international coes are used and poles and zeroes must be used.

For the CMG-5T, the only information about the sensor is the sensitivity of 1V which is is equivalent to 0.970 m/s2 or 1.03 V/ms-2. In SEISAN parameter format this should be converted to V/g so sensitivity is then

9.81 (ms-2/g)/0.97(ms-2/V) = 10.1 V/g

Parameter format

The input is:

Output format: 1 parameter format
Type of sensor: 3 It is an accelerometer
Generator constant: 10.1
Recording media gain: 312793
Amplifier gain: 0 No amplifier
Number of filters: enter No filter
File with poles and zeroes: enter We use parameters now
File with tabulated values: enter
File with measured values enter

The plot below comes up

Figure 41.3: Making response file for an accelerometer woth parameters.

A response file can now be made with e.g. A Z as component code.

Poles and zeros

The displacement response for an accelerometer consists of 2 zeros and normalizarion constant of 1. The total gain constant is then

312793 x 1.03 = 322000

The generator constant is in V/ms-2 since the two zeros transform from acceleration to displacement.

So the input file e.g. resp.txt with poles and zeros is

0 2 322000
0 0
0 0

The manual input is

Output format: 2 PAZ in SEISAN format

Type of sensor: 1 It is give input resp file

Generator constant: 1.0 Given in resp input file

Recording media gain: 1.0 Given in resp input file

Amplifier gain: 0 No amplifier

Number of filters: enter No filter

File with poles and zeroes: resp.txt Use resp.txt input file

File with tabulated values: enter

File with measured values enter

The rest is the same

The response file would then be

TEST EN Z100   0  0  0  0  0  0.000                                          P

     0    2 0.3220E+06  0.000      0.000      0.000      0.000

Making a response file for a particular station

For a particular station, chose output format SEISAN PAZ or GSE2 PAZ and later answering yes to question of making the SEISAN response file (see SEISAN manual ???????????????). If e.g. the station has station code TEST and component name S Z, the a response file valid from January 1, 2007 will have the name TEST_S__Z.2007-01-00-0000_SEI. In case of a SEISAN poles and zero file, the content is:

TEST S  Z107   0  1  0  0  0  0.000                                          P  
                                                                                
     6    3 0.5710E+21 -4.442      4.442     -4.442     -4.442     -392.0       
  850.7     -392.0     -850.7     -2199.      0.000     -475.0      0.000       
  0.000      0.000      0.000      0.000      0.000      0.000                  
             

So the file could have been made without using resp.

Table 1 Example of resp.out:

   SENSOR TYPE: SEISMOMETER       RESPONSE: DISPLACEMENT
   SEISMOMETER PERIOD=    1.00000
   GENERATOR CONSTANT=    300.000
   DAMPING RATIO     =   0.700000
   AMPLIFIER GAIN(DB)=    40.0000
   RECORDING GAIN=        2048.00
   FILTER CONSTANTS
   F= 10.00   POLES=  2
   GAIN AT 1 HZ=          2.75728E+08

  F=  0.0050   T=  200.00    AMP=      0.000000    AMPDB=-135.1    PHAS=   -90.4
  F=  0.0059   T=  169.49    AMP=      0.000000    AMPDB=-130.8    PHAS=   -90.5
  F=  0.0070   T=  142.86    AMP=      0.000000    AMPDB=-126.4    PHAS=   -90.6
  F=  0.0083   T=  120.48    AMP=      0.000001    AMPDB=-121.9    PHAS=   -90.7
  F=  0.0098   T=  102.04    AMP=      0.000001    AMPDB=-117.6    PHAS=   -90.9
  F=  0.0120   T=   83.33    AMP=      0.000002    AMPDB=-112.3    PHAS=   -91.1
  F=  0.0140   T=   71.43    AMP=      0.000004    AMPDB=-108.3    PHAS=   -91.2
  F=  0.3900   T=    2.56    AMP=      0.082352    AMPDB= -21.7    PHAS=  -125.9
  F=  0.4600   T=    2.17    AMP=      0.133868    AMPDB= -17.5    PHAS=  -133.0
  F=  0.5500   T=    1.82    AMP=      0.224204    AMPDB= -13.0    PHAS=  -142.3
  F=  0.6500   T=    1.54    AMP=      0.356744    AMPDB=  -9.0    PHAS=  -152.9
  F=  0.7700   T=    1.30    AMP=      0.554684    AMPDB=  -5.1    PHAS=  -165.6
  F=  0.9100   T=    1.10    AMP=      0.820676    AMPDB=  -1.7    PHAS=  -179.7
  F=  1.1000   T=    0.91    AMP=      1.198877    AMPDB=   1.6    PHAS=   163.3
  F=  1.3000   T=    0.77    AMP=      1.580098    AMPDB=   4.0    PHAS=   148.6
  F=  1.5000   T=    0.67    AMP=      1.933016    AMPDB=   5.7    PHAS=   137.0
  F=  1.8000   T=    0.56    AMP=      2.420457    AMPDB=   7.7    PHAS=   123.6
  F=  2.1000   T=    0.48    AMP=      2.877005    AMPDB=   9.2    PHAS=   113.5
  F=  2.5000   T=    0.40    AMP=      3.460298    AMPDB=  10.8    PHAS=   103.0
  F=  2.9000   T=    0.34    AMP=      4.027073    AMPDB=  12.1    PHAS=    94.6
  F=  3.5000   T=    0.29    AMP=      4.855642    AMPDB=  13.7    PHAS=    84.1 

FOR MORE DETAILS ON HOW TO UNDERSTAND GSE AND SEED RESPONSE PARAMETERS, SEE [Havskov and Alguacil, 2004], chapter 6.