[SAC-HELP] how to find the value of tn marker ?

[Pablo Palacios]

Dear Weitao,

I had the same necesity some time ago. I can not find a sac intruction for solve it. In my case I was looking for the maximum value of a spectrum. For reach it I made a csh script, the following lines are part of that script and could be useful. If you know another easy form to do, please tell me.

P.

# cutting the file between C1 and C2 marks and building the spectrum file
sac<<EOF
cut $C1 $C2
r ${stn}_${cmp}_${event}.sac
chnhdr A UNDEF
chnhdr F UNDEF
dft wom a
writesp am
EOF

# smoothig the spectrum and writting it as text file
sac<<EOF
r ${stn}_${cmp}_${event}.sac.am
smooth mean h 10
write over
write alpha change .am .am.alpha
EOF

# extracting the number of point of the file to compute de maximum frequency
sac<<EOF >! header
r ${stn}_${cmp}_${event}.sac.am
listhdr NPTS
EOF
            # computing the spectrum variation between consecutive points
            set delta = `awk '/NPTS/{print 25/($3-1)}' header`
            # converting the spectrum text file to spectrum column file without header (30 first lines)
            set spectrum = `echo ${stn}_${cmp}_${event}.sac.am.alpha`
            awk 'NR>30{print $0}' $spectrum | awk 'BEGIN{OFS="\n"}{print $1,$2,$3,$4,$5}' > spectrum-c
            # selecting the point of the maximum frequency and computing this value
            set MaxFreq = `awk '{if(NR==1){max=$1}else if($1>max){max=$1;print NR,max}}' spectrum-c | tail -1 | awk '{print $1}'`
            set MaxFreq = `echo $delta $MaxFreq | awk '{print $1*($2-1)}'`
            # deleting temporal work files
            rm -f header
            rm -f ${stn}_${cmp}_${event}.sac.am.alpha
            rm -f spectrum-c

# automatic picking in the spectrum file of the maximum frequency
sac<<EOF
r ${stn}_${cmp}_${event}.sac.am
chnhdr F $MaxFreq
write over
EOF

Date: Thu, 6 Nov 2008 10:37:05 -0700
From: wangwtustc at gmail.com
To: sac-help at iris.washington.edu
Subject: [SAC-HELP] how to find the value of tn marker ?

Dear All
      Is there any sac command to find the value of tn marker ? I mean if t1=100. can I find out the Y-value at that time?
thanks all.

weitao

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