Thread: Re: [Non-DoD Source] Re: Clarification on SAC transfer function

Hello again Kris,
In that case your PZs file should reflect that (see the INPUT UNIT), which
would translate into modifications of SENSITIVITY and A0 based on
instrument specification.

Januka




On Fri, 10 Aug 2018 at 07:13, Phillips-Alonge, Kristin E CIV DTRA R AND D
(US) <kristin.e.phillips-alonge.civ<at>mail.mil> wrote:

Yes, the input is always counts. But the input in counts could be
proportional to either displacement, velocity, or acceleration depending on
the instrument. According to the SAC manual for "transfer", "The default
input and output "instrument" in TRANSFER is displacement, which in SAC is
designated as NONE. Hence, if a FROM type or a TO type is not specified,
SAC assumes it to be NONE".
If my instrument (in counts) is NOT proportional to displacement, I would
normally need to say "TRANSFER FROM VEL TO VEL". In this case, since I am
using "FROM POLEZERO", there is no way to specify both the polezero and
"VEL" after "FROM" in the command. Based on your statement, I would need
to assume that "TRANS FROM POLEZERO S %pzfile to VEL" will always get me
velocity regardless of the original instrument type.

Kris

-----Original Message-----
From: Januka Attanayake [jattanayake<at>gmail.com]
Sent: Thursday, August 9, 2018 2:51 PM
To: Phillips-Alonge, Kristin E CIV DTRA R AND D (US) <
kristin.e.phillips-alonge.civ<at>mail.mil>
Cc: SAC Help <sac-help<at>lists.ds.iris.edu>
Subject: [Non-DoD Source] Re: [IRIS][sac-help] Clarification on SAC
transfer function

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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 < Caution-mailto:
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
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