Complete synthetics are computed along a horizontal profile for different water thicknesses. The source of 0.1km beneath the water - solid boundary and the receiver is 0.05km beneath this boundary. The shell script DOIWK computes the synthetics for the different models. After the synthetics are computed one can use do_mft to pick the dispersion. Because the synthetics are from a numerical model, it is possible to overlay the theoretical dispersion onto that determined by do_mft. To accomplish the overlay, the scripts MFTDOOVERLAY and PHVDOOVERLAY have been tailored to do this. For my research, these two scripts are more complicated since I present the theoretical dispersion for several models as well as current results from surface wave tomography.
The DOITWK shell script executes the wavenumber integration codes to create the
synthetics for all Green's functions.
The initial appearance of the OCEAN_SW
directory is
> ls -F
00README PHVDOOVERLAY* tOCEAN_2.0.mod MFTDOOVERLAY* tOCEAN_1.0.mod tOCEAN_4.0.mod DOITWK* tOCEAN_3.0.mod tOCEAN_5.0.mod
After executing the DOITSW command this directory will
appear as
>ls -F
00README THF.PLT tOCEAN_3.0.mod wkDIR_2.0/ DOITWK* ZVF.PLT tOCEAN_4.0.mod wkDIR_3.0/ MFTDOOVERLAY* tOCEAN_1.0.mod tOCEAN_5.0.mod wkDIR_4.0/ PHVDOOVERLAY* tOCEAN_2.0.mod wkDIR_1.0/ wkDIR_5.0/
The subdirectories, such as wkDIR_3.0 for the 3.0km water
thickness, will have files with names such as:
> ls -F
00400000_003100_003050.RDD 00400000_003100_003050.ZDS 00400000_003100_003050.RDS 00400000_003100_003050.ZSS 00400000_003100_003050.RHF 00400000_003100_003050.ZEX 00400000_003100_003050.RSS 00400000_003100_003050.ZVF 00400000_003100_003050.REX 00400000_003100_003050.ZHF 00400000_003100_003050.RVF MFTDOOVERLAY* 00400000_003100_003050.TDS PHVDOOVERLAY* 00400000_003100_003050.TSS slegn96.egn 00400000_003100_003050.THF sregn96.egn 00400000_003100_003050.ZDD tOCEAN_3.0.mod
Note that the model files differ from those use to compute the dispersion because the number of deep layers are truncated. This is acceptable since the effect of deeper structure will not affect the waveforms at short epicentral distances.
To start the process the epicentral distances and timing information is defined in the file dfile. Given that one expects slow arrives because of the lower velocities near the surface, 1024 point time series are constructed. A sample rate of 1.0s is used since it is expected that the ambient noise studies will only provide information at longer periods. finally to speed the process, the first sample of the synthetics will be at a time one second before a distance (km) / 8.0 (km/s) arrival.
Next work directories are created for each model. Note the care in naming the model files and the directories.
The wavenumber integration codes are run and the resulting time series are converted to Sac files use the program f96tosac. This program has options for the naming of files. I have selected -FMT 2 here since f96tosac -h indicates that the Green's functions will have names such as DDDDDddd_HHHhhh_ZZZzzz.grn, which means that the file name can express distances and depths to the nearest meter, or epicentral distance of DDDDD.ddd km, source depth as HHH.hhh km and receiver depth as ZZZ.zzz km.
Since the purpose of this tutorial is to compare the dispersion that derived from the seismogram to the theoretical values for the given velocity mode, the shell scripts MFTDOOVERLAY and >PHVDOOVERLAY are copied into the subdirectory. In addition, the required eigenfunctions files are copied into the same directory. Note that DOITWK knows where these eigenfunction files are located.
the DOIT.WK script is
#!/bin/sh
#####
# define the distance range profile
# We need a window between P and about 1.0 km/s
#####
cat > dfile << EOF
100.0 1.0 1024 -1 8.0
200.0 1.0 1024 -1 8.0
300.0 1.0 1024 -1 8.0
400.0 1.0 1024 -1 8.0
500.0 1.0 1024 -1 8.0
EOF
for D in 1.0 2.0 3.0 4.0 5.0
do
if [ ! -d wkDIR_${D} ]
then
mkdir wkDIR_${D}
fi
# place the source and receiver in the solid
# is is assumed the the D is actually the the thickness of
# the first layer for long periods we will place the
# source 100m beneath the water - solid boundary. The
# receiver is 50 below. The reason for the different depths
# is tha tthe computations will not work well for the
# source and reciever at the same depths
#####
cp tOCEAN_${D}.mod wkDIR_${D}
# run in a sub shell
(
cd wkDIR_${D}
cp ../dfile .
HS=`echo $D | awk '{print $1 + 0.10 }'`
HR=`echo $D | awk '{print $1 + 0.05 }'`
hprep96 -d dfile -M tOCEAN_${D}.mod -HS ${HS} -HR ${HR}
hspec96
hpulse96 -V -p -l 1 | f96tosac -FMT 2
# for later analysis copy the eigenfunctions
# for the model, if they exist
if [ -d ../../OCEAN_SW/swDIR_${D} ]
then
cp ../../OCEAN_SW/swDIR_${D}/*.egn .
fi
cp ../MFTDOOVERLAY ../PHVDOOVERLAY .
# clean up
rm -f hspec96.??? dfile
)
done
#####
# clean up
#####
rm -f dfile
#####
When do_mft calls sacmft96, the files MFT96CMP and PHV96CMP are created in the work directory. These are prototype shell scripts that permit the user to create plot files to overlay onto the MFT96.PLT and PHV96.PLT. These files know everything about these plots, e.g., position on the screen and the mapping of dispersion and amplitude to the screen to permit the overlay. The contents of these files look like
> cat MFT96CMP
#!/bin/sh
# Data file = 00500000_005100_005050.THF
# alpha = 25.000
sdpegn96 -X0 5.10 -Y0 1.50 -XLEN 4.00 -YLEN 4.00 -XMIN 2.00 -XMAX 100. \
-YMIN 0.10 -YMAX 5.00 -PER -L -U -NOBOX -XLOG -YLIN
sacspc96 -X0 1.30 -Y0 1.50 -XLEN 3.00 -YLEN 4.00 -XMIN 1.41 -XMAX 141. \
-YMIN 0.100E-06 -YMAX 0.100E-03 -PER -NOBOX -XLOG -YLOG \
-f 00500000_005100_005050.THF
> cat POM96CMP
#!/bin/sh
# Data file = 00500000_005100_005050.THF
# alpha = 25.000
sdpegn96 -X0 5.10 -Y0 1.50 -XLEN 4.00 -YLEN 4.00 -XMIN 2.00 -XMAX 100. \
-YMIN 0.10 -YMAX 5.00 -PER -L -C -NOBOX -XLOG -YLIN
For use with do_mft only the sdpegn96 lines are important.
To permit the dispersion overlays, do_mft executes the scripts MFTDOOVELAY and PHVDOOVERLAY. The first task is to extract the sdpegn96 command form the MFT96CMP and the PHV96CMP. Then the command line is modified to specify a color of the dispersion overlay - white for group velocity and red for phase velocity, so that the dispersion is actually visible. The modified shell script is 1.tmp which is executed. Finally resultant PLT file is overlay onto the original MFT96.PLT or PHV96.PLT. After the overlay script is run, do_mft replots its page.
#!/bin/sh
######
# do_mft (sacmft96) will create the files MFT96CMP
# and PHV96CMP which are prototypes for
# creating a dispersion plot for overlay onto
# MFT96.PLT and PHV96.PLT, respectively
######
# theoretical in white
KOLOR=0
grep sdpegn96 MFT96CMP > 1.tmp
ed 1.tmp > /dev/null 2>&1 << EOF
/sdpegn96/s//sdpegn96 -K ${KOLOR} /
w
q
EOF
sh 1.tmp > /dev/null 2>&1
cat S?EGNU.PLT >> MFT96.PLT
#####
# clean up
#####
rm S?EGN?.PLT
#!/bin/sh
######
# do_mft (sacmft96) will create the files PHV96CMP
# and PHV96CMP which are prototypes for
# creating a dispersion plot for overlay onto
# PHV96.PLT and PHV96.PLT, respectively
######
# theoretical in red
KOLOR=2
grep sdpegn96 PHV96CMP > 1.tmp
ed 1.tmp > /dev/null 2>&1 << EOF
/sdpegn96/s//sdpegn96 -K ${KOLOR} /
w
q
EOF
sh 1.tmp > /dev/null 2>&1
cat S?EGNC.PLT >> PHV96.PLT
#####
# clean up
#####
rm S?EGN?.PLT