SU Name Description Byte Length
------- --------------------------------- ---- ------
tracl trace
sequence number within line 1 4
tracr trace sequence number within reel 5 4
fldr field record number 9 4
tracf trace number within field record 13 4
ep energy source point number 17 4
cdp CDP ensemble number 21 4
cdpt trace number within CDP ensemble 25 4
trid trace identification code: 29 2
1 = seismic data
2 = dead
3 = dummy
4 = time break
5 = uphole
6 = sweep
7 = timing
8 = water break
9---, N = optional use
nvs number of vertically summed traces 31 2
nhs number of horizontallysummed
traces 33 2
duse data use: 1
= production, 2 = test 35 2
offset distance from
source point to receiver 37 4
group (negative if opposite to
direction in which the
line was shot)
gelev receiver group elevation from sea level 41 4
(above sea level is positive)
selev source elevation from sea level 45 4
(above sea level is positive)
sdepth source depth (positive) 49 4
gdel datum elevation at receiver group 53 4
sdel datum elevation at source 57 3
swdep water depth at source 61 4
gwdep water depth at receiver group 65 4
scalel scale factor for previous 7
entries 67 2
with value plus or minus 10 to the
power 0, 1, 2, 3, or 4 (if
positive,
multiply, if negative divide) 69 2
scalco scale factor for next 4
entries
with value plus or minus 10 to the
power 0, 1, 2, 3, or 4 (if
positive,
multiply, if negative divide)
sx X source coordinate 73 4
sy Y source coordinate 77 4
gx X group coordinate 81 4
gy Y group coordinate 85 4
counit coordinate units code: 89 2
for previous four entries
1 = length (meters or feet)
2 = seconds of arc (in this case, the
X values are longitude and the Y values
are latitude, a positive value designates
the number of seconds east of
or north of the equator
wevel weathering velocity 91 2
swevel subweathering
velocity 93 2
sut uphole time at
source 95 2
gut uphole time at receiver group 97 2
sstat source static correction 99 2
gstat group static correction 101 2
tstat total static applied 103 2
laga lag time A, time in ms between end of 105 2
240-byte trace identification header
and time
break, positive if time break
occurs
after end of header, time break
is
defined as the initiation pulse
which
maybe recorded on an auxiliary
trace or
as otherwise specified by
the
recording system
lagb lag time B, time in ms between the 107 2
time break and the initiation time of
the energy source, may be positive
or negative
delrt delay
recording time, time in ms 109 2
between initiation time of energy
source and time when recording of
data samples begins(for deep water
work if recording does not start
at zero time)
muts mute time—start 111 2
mute mute time—end 113 2
ns number of
samples in this trace 115 2
dt sample
interval; in micro-seconds 117 2
gain gain type
of field instruments code: 119 2
1 = fixed
2 = binary
3 = floating point
4 ---- N = optional use
igc instrument gain constant 121 2
igi instrument early or initial gain 123 2
corr correlated:1 = no, 2 = yes 125 2
sfs sweep frequency at start 127 2
sfe sweep frequency at end 129 2
slen sweep length in ms 131 2
styp sweep type code: 133 2
1 = linear
2 = cos-squared
3 = other
stas sweep trace length at start in ms 135 2
stae sweep trace length at end in ms 137 2
tatyp taper type:
1=linear, 2=cos^2, 3=other 139 2
afilf alias filter frequency if used 141 2
afils alias filter slope 143 2
nofilf notch filter frequency if used 145 2
nofils notch filter slope 147 2
lcf low cut
frequency if used 149 2
hcf high cut frequncy
if used 151 2
lcs low cut slope 153 2
hcs high cut slope 155 2
year year data recorded 157 2
day day of
year 159 2
hour hour of day
(24 hour clock) 161 2
minute minute of
hour 163 2
sec second of
minute 165 2
timbas time basis code: 1 = local, 2
= GMT, 167 2
3 = other
trwf trace weighting factor, defined as 169 2
1/2^N volts for the least significant
bit
grnors geophone group number of roll
switch 171 2
position one
grnofr geophone group number of trace
one 173 2
within original field record
grnlof geophone
group number of last trace 175 2
within original field record
gaps gap size
(total number of groups 177 2
dropped)
otrav overtravel taper
code: 1 = down 179 2
(or behind), 2 = up (or
ahead)
d1 sample
spacing for non-seismic data 181 4
f1 first
sample location for non-seismic 185 4
data
d2 sample
spacing between traces 189 4
f2 first
trace location 193 4
ungpow negative of power used for
dynamic 197 4
range compression
unscale reciprocal of scaling factor to 201 4
normalize range
ntr number of traces 205 4
mark mark selected
traces 209 2
shortpad alignment padding 211 2
unass unassigned 213 28
NOTE: All
headers are integer, except d1, f1, d2, f2, ungpow,
and unscale, which are IBM
floating-point.