[SAC-HELP] Calculating the CONSTANT to use to remove instument response

Chad Trabant chad at iris.washington.edu
Wed Apr 8 21:13:57 PDT 2009


Hello Melaku Bogale,

You need to know the total sensitivity of the digitizer, this is the  
value which relates digital counts to ground units.  The poles and  
zeros only represent the sensor.  The CONSTANT in the SAC poles and  
zeros file should be the total sensitivity multiplied by the  
normalization factor for the poles and zeroes.  The value for CONSTANT  
depends on the units desired also.

Chad
IRIS DMC

On Apr 8, 2009, at 3:50 PM, Melaku Ayenew wrote:

> Hi All,
> I am trying to remove instrument responses from STS_2, CMG3T. CMG_ES  
> broadband instruments. I got the poles and zeros from IRIS Pascal  
> Instrumentation. But I have difficulty figuring out what constant I  
> should use in the *.pz file that has to read by the SAC TRANSFER  
> command. For example, I was trying to synthesis a WA seismogram by  
> removing the STS_2 response and convoulating the WA response. I used  
> a constant of 1 in this calcultion. The synthesis seismogrm looks  
> good but the displacemnt values don't make sense (they are several  
> hunderd meters). I understand it is because of the CONSTANT=1 I put.  
> My Question is How can I calculate the correct CONSTANT that I need  
> to put with the zeros and poles in the SAC *.pz file. The IRIS  
> PASCAL instrumentation page gives the zeros and poles and a  
> normalization factor.
> I greatly appreciate your help in this matter.
>
> Melaku Bogale
> New Mexico State University
> Department of Physics
> Las Cruces NM 88003-8001
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