[SAC-HELP] Having problems creating ALPHA input files

[Robert Casey]

	Hi Carlos (cpena at email.arizona.edu)-


> Did you read ac_new[1].dat using the RA command in a linux version of 
> SAC?.

	No, I performed this operation on a Mac.

> Before I tried your scheme, I just tried to read the file you created 
> using RA
> and SAC responds with "WARNING: Trouble reading line. Skipping ... 
> (list of 5
> column data points)"; one message per row of data points, and after it 
> finishes
> with the warning messages it states "Segmentation fault" and proceeds 
> to kick me
> out of SAC. The same thing happended to me when I tried to read one 
> column data.

	Not sure why this happens on the Linux machine.  The text file has New 
Line characters for line terminators and I would think it would work 
fine on a Linux box.

>
> Moreover, when I convert a SAC format data file to an ALPHA format 
> data file,
> the resulting data file is all "screwed up". SAC changes all the header
> information and considers only a fraction of the data points. You can 
> try this
> by doing FG SEISMOGRAM and converting the resulting data file from SAC 
> to
> ALPHA.

	Not sure of the reasons for this.  Might be worth trying 
space-separated data fields instead of tabs.  I was taking a first 
guess at a solution.

>
> Could there be a bug in the linux version of SAC?; other people I've 
> talked to
> tried it in a MAC version, using RA on one column data and no header 
> info and
> it worked OK.

	I have no idea if there is a bug with the Linux version.  We don't yet 
have good tabulation of known issues for SAC here at IRIS (as far as I 
am aware).  I think it may be that the Mac-created text file

>
> By the way, since you got it to plot, can you send me the raw 
> acceleration time
> series plot, followed by a filtered acceleration, velocity and 
> displacement
> time series plots?. Consider a 4th degree Butterworth low pass filter 
> with a
> lowcut at 4 Hz to filter raw acceleration points and a 4th degree 
> Butterworth
> high pass filter with a high cut at 2 Hz for velocity and displacement 
> time
> series. Please normalize acceleration time series with respect to the 
> mean
> BEFORE you apply filter and also normalize with respect to mean 
> velocity and
> displacement time series AFTER you apply the filter.

	This is something I don't have experience with or the time to work 
with.  Perhaps a more SAC-inclined user can step in and help you with 
your processing issue.  (anyone?)  I was trying to demonstrate that 
through a UNIX shell it is not difficult to convert a single column of 
text data to five columns of data.  Beyond this, it's getting out of my 
depth to manage in a time-effective manner.

	-Rob