Sigsbee2 Models

Free surface model

A SConstruct script found at sigsbee/data2B/fs/ is presented in Table 7. This script reads the segy source file and converts it to Madagascar's RSF format and appends the header as necessary. The free surface boundary present within this model allows for the generation of reflections at the model edges.

 #######################################
 # Sigsbee 2B Free Surface Shot Data   #
 #######################################

from rsf.proj import *

#---- Define Variables and Filenames ---#
data = 'sigsbee2b_fs.segy'

#------- Import Data ----------#
#- Uses ftp program Fetch
Fetch(data ,'sigsbee')

#-----  Convert Data ----------#
Flow('zdata tzdata ./dhead ./bdhead',data,
     '''
     segyread
     tape=$SOURCE
     tfile=${TARGETS[1]}
     hfile=${TARGETS[2]}
     bfile=${TARGETS[3]}
     ''',stdin=0)

# create sraw(t,o,s): o=full offset, s=shot position, t=time

Flow('ss','tzdata','dd type=float | headermath output="10925+fldr*150" | window')
Flow('oo','tzdata','dd type=float | headermath output="offset"         | window')
Flow('si','ss','math output=input/150')
Flow('oi','oo','math output=input/75')
Flow('os','oi si','cat axis=2 space=n ${SOURCES[1]} | transp | dd type=int')
Flow('sraw','zdata os',
     '''
     intbin head=${SOURCES[1]} xkey=0 ykey=1
     ''')
Flow('shotFs2B','sraw',
     '''
     put
                           label1=Time       unit1=s
        d2=.02286 o3=0     label2=Offset     unit2=km
        d3=.04572 o3=3.330 label3=Shot-coord unit3=km |
     mutter half=false t0=1.0 v0=6000
     ''')

#-------- Plot Data --------#
Result('zero2Bfs','shotFs2B','''window $SOURCE min2=0 max2=0 size2=1
    | grey  pclip=98 color=I screenratio=1.5 gainpanel=a
    label2=Position label1=Time title= label3=  unit2=km unit1=s
    labelsz=3''')

Result('shot702Bfs','shotFs2B','''window $SOURCE n3=1 f3=70 |
    grey  pclip=99 color=I gainpanel=a wantframenum=y  unit1=s label1=Time
    label2=Offset unit2=km label3=Shot unit3=km title=
    screenratio=1.35 labelsz=3''')

End()

Table 7. Contents of data2B/fs/SConstruct script.

Again shot number 70, fired 6.5 km into the model, is plotted in Figure 5. The precise coordinates of the shot are shown in the lower left hand corner of the figure. The zero offset data is presented in Figure 6.

shot702Bfs
Figure 5. Shot number 70 performed on sigsbee 2B FS model. The shot location is presented in the lower left hand corner of the plot

zero2Bfs
Figure 6. Sigsbee2B free surface boundary zero offset data.

Sigsbee2 Models