Thread: Re: sac-help Digest, Vol 39, Issue 1

Started: 2008-10-26 05:18:20
Last activity: 2008-10-26 05:18:20
Topics: SAC Help
Anne Deschamps
2008-10-26 05:18:20
Hi

I would like to use the type evalresp to compute the signal corrected
from the instrumental response (files provided by rdseed).

What is the IDEP value which should be insered in the header to say that
I have raw data? Presently in my data IDEP is not defined

I have accelerometric data.

What is the result on accelerometric data of the command
transfer from evalresp to none

What is the result of
transfer from evalresp to acc
the amplitudes are different (even after removing the high frequencies...)
the IDEP in one is ACCELERATION (CM/SEC/SEC)
in the other DISPLACEMENT (NM)

the RESP file indicates
B053F05 Response in units lookup: M/S**2 - Acceleration

So if you could give me the rules, it will be great as presently the
result is not what we expect. May be there is a compatibility problem of
our RESP file.

from yours indications I will try to find the rule for the velocimetric
data.
Thanks

Anne Deschamps

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Today's Topics:

1. GSE writing (Sheila Peacock)
2. response spectra (Olga-Joan Ktenidou)
3. how does SAC define the header variable CMPINC, exactly?
(Val Zimmer)
4. Re: how does SAC define the header variable CMPINC, exactly?
(Frederik Tilmann)
5. Re: [sac-dev] [Fwd: GSE writing] (Brian Savage)
6. Re: [sac-dev] [Fwd: GSE writing] (Brian Savage)
7. Do Loop Bug (Bob Hancock)


----------------------------------------------------------------------

Message: 1
Date: Tue, 30 Sep 2008 09:57:34 +0100
From: Sheila Peacock <s.peacock<at>blacknest.gov.uk>
Subject: [SAC-HELP] GSE writing
To: sac-help<at>iris.washington.edu
Message-ID: <48E1E9FE.5020002<at>blacknest.gov.uk>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

(re-sent)


Dear All,

SAC v. 101.1 either fails or crashes when I try to use "writegse". SAC v. 100 is OK
with writegse. Is this a known bug?

Regards,
Sheila Peacock.

SAC v. 100 (is OK)
$ sacb
SEISMIC ANALYSIS CODE [03/01/2005 (Version 100.00)]
Copyright 1995 Regents of the University of California

SAC> r 1986.213.14.03.12.3600.DW.COL..SHZ.D.SAC
SAC> writegse 198608011403COL.gse.int
Converting waveforms .
Writing station data .
Writing channel data .
Writing arrival data .
1 waveforms written in 198608011403COL.gse.int
SAC> end


SAC v. 101.1 fails:

$ sac1011
SEISMIC ANALYSIS CODE [01/19/2008 (Version 101.1)]
Copyright 1995 Regents of the University of California

SAC> r 1986.213.14.03.12.3600.DW.COL..SHZ.D.SAC
SAC> writegse 198608011403COL.gse.int
Segmentation fault


or.... (trying various parameters in the parameter list)

SAC> r 1986.213.14.03.12.3600.DW.COL..SHZ.D.SAC
SAC> writegse int 198608011403COL.gse.int
ERROR 1312: Bad number of files in write file list:
SAC> writegse int source off 198608011403COL.gse.int
ERROR 1312: Bad number of files in write file list:
SAC> writegse int source off commit 198608011403COL.gse.int
ERROR 1312: Bad number of files in write file list:

$ sac1011
SEISMIC ANALYSIS CODE [01/19/2008 (Version 101.1)]
Copyright 1995 Regents of the University of California

SAC> r 1986.213.14.03.12.3600.DW.COL..SHZ.D.SAC
SAC> writegse CM6 198608011403COL.gse.cm6
Segmentation fault



------------------------------

Message: 2
Date: Wed, 1 Oct 2008 13:09:22 -0500
From: "Olga-Joan Ktenidou" <ktenidou<at>civil.auth.gr>
Subject: [SAC-HELP] response spectra
To: <sac-help<at>iris.washington.edu>
Message-ID:
<00ab01c923f0$d7db81a0$49e7f884<at>isismologica.iingen.unam.mx>
Content-Type: text/plain; charset="iso-8859-1"

dear all,

just wondering if anyone had come across a way to calculate response spectra through sac..
any help/suggestion much appreciated!
thanks,

olga

----
Olga-Joan Ktenidou
Aristotle University of Thessaloniki
Department of Civil Engineering
Lab. of Soil Mechanics, Foundation Eng. & Geotechnical Earthquake Eng.
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Message: 3
Date: Tue, 07 Oct 2008 13:35:54 -0700
From: Val Zimmer <valzimmer<at>berkeley.edu>
Subject: [SAC-HELP] how does SAC define the header variable CMPINC,
exactly?
To: sac-help<at>iris.washington.edu
Message-ID: <48EBC82A.2090300<at>berkeley.edu>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Hello SAC users,

I have a dataset from a station that was NOT placed perfectly level -
e.g. the sensor was placed on a ledge that had a little bit of tilt,
such that Z is not perfectly up/down, and N + E have some down or upward
component in the data. I'm now trying to analyze that data, but have
yet to find a good definition of cmpinc in the manual (all it says is
"Component incident angle (degrees from vertical)"). CMPINC has no
inherent orientation (like CMPAZ, from north, and looking down with 90
to the right e.g. east), but I can think of only one good, logical way
to define cmpinc. Although, I'm probably missing something, and would
like to verify that this is correct, hence the email to you all.

I can infer the following things from pulling the data from an
earthquake seismology station (cmb.bk):

* +Z is probably up, (not down like in the oilfield): Up = 0, hence
Down = 180.
* the other components have cmpinc = 90 (N + E)
* Therefore, the direction of the cmpinc vector *must* be relative
to the cmpaz vector AND that cmpinc vector corresponds to apparent
tilt along that vector (not absolute/maximum tilt for the whole
instrument in whatever direction that happens to be).
* It follows other axes would have to be defined as follows:
o DIR CMPAZ CMPINC
o south 180 90
o west 270 90
o n + a little up 0 75
o e + a little down 90 110

Can anyone tell me if this reasoning is correct, and if not, point me to
some documentation with a clear definition?

Oh, and if any of you know how Antelope defines the <vang> vector, I'm
also trying to figure that out (I think that Antelope's definition of
"vertical" is different, e.g. Up = 180 and Down = 0, although, I cannot
confirm it).

Thanks for your time!
Valerie Zimmer


------------------------------

Message: 4
Date: 08 Oct 2008 00:19:21 +0100
From: Frederik Tilmann <fjt21<at>cam.ac.uk>
Subject: Re: [SAC-HELP] how does SAC define the header variable
CMPINC, exactly?
To: Val Zimmer <valzimmer<at>berkeley.edu>
Cc: sac-help<at>iris.washington.edu
Message-ID: <Prayer.1.3.0.0810080019210.6235<at>hermes-1.csi.cam.ac.uk>
Content-Type: text/plain; format=flowed; charset=ISO-8859-1

Dear Valerie

as far as I know your interpretation is essentially correct except that I
am not entirely clear with what you mean by
* Therefore, the direction of the cmpinc vector *must* be relative
to the cmpaz vector AND that cmpinc vector corresponds to apparent
tilt along that vector (not absolute/maximum tilt for the whole
instrument in whatever direction that happens to be).

If you think of each component as a vector then cmpinc is the angle the
vector makes with vertical up, and cmpaz is the azimuth clockwise from
north of the horizontal projection of the component vector. It does not
make sense to talk about the cmpinc or cmpaz vector. For cmpinc=0 or
cmpinc=180 the value of cmpaz is irrelevant, of course. As far as I know
nowhere in SAC is cmpinc actually used except to check whether components
are horizontal for application of the "rot to gcp" command.

A few years back I wrote a SAC command to rotate an arbitrarily oriented
sensor (3 components needed to be perpendicular) into either VRT, ZNE, or
LQT system, and this command used cmpinc. This used the extern mechanism of
sac2000 but I am not sure whether this way of loading up user-defined
commands works with the more recent versions of sac. If you are interested
I can send you the source.

Regards
Frederik








On Oct 7 2008, Val Zimmer wrote:

Hello SAC users,

I have a dataset from a station that was NOT placed perfectly level -
e.g. the sensor was placed on a ledge that had a little bit of tilt,
such that Z is not perfectly up/down, and N + E have some down or upward
component in the data. I'm now trying to analyze that data, but have
yet to find a good definition of cmpinc in the manual (all it says is
"Component incident angle (degrees from vertical)"). CMPINC has no
inherent orientation (like CMPAZ, from north, and looking down with 90
to the right e.g. east), but I can think of only one good, logical way
to define cmpinc. Although, I'm probably missing something, and would
like to verify that this is correct, hence the email to you all.

I can infer the following things from pulling the data from an
earthquake seismology station (cmb.bk):

* +Z is probably up, (not down like in the oilfield): Up = 0, hence
Down = 180.
* the other components have cmpinc = 90 (N + E)
* Therefore, the direction of the cmpinc vector *must* be relative
to the cmpaz vector AND that cmpinc vector corresponds to apparent
tilt along that vector (not absolute/maximum tilt for the whole
instrument in whatever direction that happens to be).
* It follows other axes would have to be defined as follows:
o DIR CMPAZ CMPINC
o south 180 90
o west 270 90
o n + a little up 0 75
o e + a little down 90 110

Can anyone tell me if this reasoning is correct, and if not, point me to
some documentation with a clear definition?

Oh, and if any of you know how Antelope defines the <vang> vector, I'm
also trying to figure that out (I think that Antelope's definition of
"vertical" is different, e.g. Up = 180 and Down = 0, although, I cannot
confirm it).

Thanks for your time!
Valerie Zimmer
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