Thread: Clarification on SAC transfer function

Hi,

See inline answers.

HTH,

Milton


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Milton P. PLASENCIA LINARES

Centro di Ricerche Sismologiche (CRS)
OGS - Istituto Nazionale di Oceanografia e di Geofisica Sperimentale

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On Thu, 9 Aug 2018 at 15:58, Phillips-Alonge, Kristin E CIV DTRA R AND D
(US <kristin.e.phillips-alonge.civ<at>mail.mil> wrote:

Hello,

I have some IRIS data converted to SAC format along with the corresponding
polezero files and want to use "transfer" along with the pzfiles to perform
the deconvolution to remove instrument response.



I know that the SAC transfer function is expecting a displacement input.

Why?, I think it is not correct, sac transfer function "look" in the poles
and zeros files,
during the conversion (response files to P&Z, the P&Z files have add an
extra Zero), so
is not necessary to specify TO NONE it is default value.
So if you have a velocimeter you give to sac transfer function counts/m/s
I you have accelerometer you give counts/m2/s (P&Z will have two zeros
extra)

If I am using "TRANS FROM POLEZERO S %pzfile to NONE"

"to none" means output in displacement ( your P&Z file have an zero extra )

or "TRANS FROM POLEZERO S %pzfile to VEL"

here the output is velocity obviously ( sac remove ( not use) the zero
extra in P&Z file)

and my input actually is a displacement,



I expect the output to be the displacement for the first command and
velocity for the latter command.

This is correct for me if you give counts/m/s as input

However if my input is actually proportional to velocity rather than
displacement as expected by the transfer function, does the "TRANS FROM
POLEZERO S %pzfile to NONE" actually give me velocity?

No, "TO NONE" give you displacement, and this output is used to calculate
magnitude...

Give a look I the transfer command,
SAC> help transfer

And check old e-mails in the list about transfer command.


Thanks for any clarification

Kris

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Hello Kris,
Your input time series should be in counts, not displacement, not velocity.
If your input trace is velocity or displacement, there is no need to use
Transfer in the first place.

Januka

On Thursday, 9 August 2018, Phillips-Alonge, Kristin E CIV DTRA R AND D (US
<kristin.e.phillips-alonge.civ<at>mail.mil> wrote:

Hello,

I have some IRIS data converted to SAC format along with the corresponding
polezero files and want to use "transfer" along with the pzfiles to perform
the deconvolution to remove instrument response. I know that the SAC
transfer function is expecting a displacement input. If I am using "TRANS
FROM POLEZERO S %pzfile to NONE" or "TRANS FROM POLEZERO S %pzfile to VEL"
and my input actually is a displacement, I expect the output to be the
displacement for the first command and velocity for the latter command.
However if my input is actually proportional to velocity rather than
displacement as expected by the transfer function, does the "TRANS FROM
POLEZERO S %pzfile to NONE" actually give me velocity? Thanks for any
clarification

Kris

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Januka Attanayake
Research Fellow | Earthquake Seismology
Homepage: http://sites.google.com/site/janukaattanayake

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