Objective
During this assignment you will use generalized ray theory to make
synthetics
to study the excitation of Rayleigh waves from dislocation sources.
Procedure
Step 1:
Create a velocity model with the following parameters: layer thickness
40 km, Vp = 6.0 km/s, Vs= 3.5 km/sec, Density=2.8 gm/cm3
, Qp= 0, Qs=0, Etap=0, Etas=0, Frefp=1, frefs=1
Step 2:
Create a distance file with entries
100. 0.050 1024 0.0 0.0
Step 3:
Put Steps 1 and 2 into a shell script, then create the following in the
shell script
rm -fr mile96
for HR in 0.0
do
gprep96 -M 2half.mod -DOALL -N 6 -HS 10.0 -HR ${HR} -DOCONV
genray96 -d dfile > genray96.out
gpulse96 -p -l 4 >> mile96
done
f96tosac -B < mile96
This will create the file FPROF96.PLT, which will be the seismographs
at a distance of 100 km for a source at a depth of 10 km in a vertical
depth profile from 0.0 to 7.0 km.
For the purpose of illustration, the signal is filtered between 0.25
and 0.50 Hz to focus on the behavior of the Rayleigh wave near a
frequency of 0.25 - 0.50 Hz.
Questions:
Where is the Rayleigh wave!
What is the particle motion of the P wave?
What is the particle motion of the Rayleigh wave for a receiver
at the surface and for a receiver at a depth of 7.0 km?
What happens to the radial component of the Rayeigh wave near a depth
of 2.0km?
Step 3:
Modify the script above to compute the broadband Rayleigh wave for the
receiver at the surface. DO NOT apply the fbutt96 filtering step.
Also call the output file mile96 and convert the traces to a SAC format:
rm -fr mile96
for HR in 0.0
do
gprep96 -M 2half.mod -DOALL -N 6 -HS 10.0 -HR ${HR} -DOCONV
genray96 -d dfile > genray96.out
gpulse96 -p -l 4 >> mile96
done
f96tosac -B < mile96
Then use gsac to overlay the traces for the ZDD Green's function:
gsac
GSAC> r B00101ZDD.sac B00102RDD.sac
GSAC> lp c 0.2 n 2
GSAC> hp c 0.02 n 2
GSAC> color list red blue
GSAC> fileid name
GSAC> color list red blue
GSAC> p overlay on
GSAC> bg plt
GSAC> p overlay on
Hold is OFF
XLIM is turned off
Initializing P001.PLT
GSAC> plotnps -=F7 -W10 -EPS -G < P001.PLT > P001.ps
(this figurs P001.ps can be printed on
the PostScript Printers as lpr -Plx1
P001.ps
Questions:
What is the particle motion of the Rayeigh wave? (vertical is up and
radial is away from the source)
What is the ratio of the radial to vertical amplitude - you can see
this better if you take the hilber transform of the radial, and
then overlay
Modify the script byt DO NOT filter the traces and IDENTITY the
folowing phases: P, sP, and S.
Compare the observed and predicted travel times of the P, sP and S
arrivals for a source depth of 10 km and an epicentral distance of 100
km.
If the sP particle motion actually that of P?