The SEG-Y defined data trace header values (Barry and others, 1975).
The SEG-Y files on this CD-ROM conform to this standard.

Byte Numbers   Header Value Description
1 - 4          Trace sequence number within line.
5 - 8          Trace sequence number within file (reel).
9 - 12         original field record number.
13 - 16        Trace number within original field record.
17 - 20        Energy source point number.
21 - 24        CDP ensemble number.
25 - 28        Trace number within the CDP ensemble.
29 - 30        Trace identification code:    1 = seismic data
                                        2 = dead
                                        3 = dummy
                                        4 = time break
                                        5 = uphole
                                        6 = sweep
                                        7 = timing
                                        8 = water break
                                        9 = N, optional use, N =
                                            32,767
31 - 32        Number of vertically summed traces yielding this
               trace.
33 - 34        Number of horizontally stacked traces yielding
               this trace.
35 - 36        Data use:                1 = production
                                        2 = test
37 - 40        Distance from source point to receiver group.
41 - 44        Receiver group elevation - above sea level are
               positive, below sea level are negative.
45 - 48        Surface elevation at source.
49 - 52        Source depth below surface (positive number).
53 - 56        Datum elevation at receiver group.
57 - 60        Datum elevation at source.
61 - 64        Water depth at source.
65 - 68        Water depth at group.
69 - 70        Scalar to be applied to all elevations & depths,
               specified in bytes 41 - 68 to give the real value.
               Scalar = 1, +/-10, +/-100, +/-1000, or +/-10,000.
               If positive, scalar is used as a multiplier; if
               negative, scalar is used as a divisor.
71 - 72        Scalar to be applied to all coordinate specified
               in bytes 73 - 88 to give the real value.  Scalar =
               1, +/-10, +/-100, +/-1000, or +/-10,000.  If
               positive, scalar is used as a multiplier; if
               negative, scalar is used as a divisor.
73 - 76        Source coordinate - X.
77 - 80        Source coordinate - Y.
81 - 84        Group coordinate - X.
85 - 88        Group coordinate - Y.
               If the coordinate units are in seconds of arc, the
               X values represent longitude and the Y values
               represent latitude.  A positive value designates
               the number of seconds east of Greenwich Meridian
               or north of the equator and a negative value
               designates the number of seconds south or west.
89 - 90        Coordinate units:        1 = length (meters or
               feet)
                                        2 = seconds of arc
91 - 92        weathering velocity.
93 - 94        Subweathering velocity.
95 - 96        Uphole time at source.
97 - 98        Uphole time at group.
99 - 100       Source static correction.
101 - 102      Group static correction.
103 - 104      Total static applied.
105 - 106      Lag time A.  Time in ms between end of 240-byte
               trace identification header and time break.
               positive if time break occurs after end of header,
               negative if time break occurs before end of
               header.  Time break is defined as the initiation
               pulse which may be recorded on an auxiliary trace
               or as otherwise specified by the recording system.
107 - 108      Lag time B.  Time in ms between the time break and
               the initiation time of the energy source.  May be
               positive or negative.
109 - 110      Delay recording time.  Time in ms between
               initiation time of energy source and time when
               recording of data samples begins.
111 - 112      Mute time - start.
113 - 114      Mute time - end.
115 - 116      Number of samples in this trace.
117 - 118      Sample interval, in microseconds, for this trace.
119 - 120      Gain type of field instruments:    1 = fixed
                                        2 = binary
                                        3 = floating point
                                        4 = --- N = optional use
121 - 122      Instrument gain constant.
123 - 124      Instrument early or initial gain (db).
125 - 126      Correlated:              1 = no
                                        2 = yes
127 - 128      Sweep frequency at start.
129 - 130      Sweep frequency at end.
131 - 132      Sweep length, ms.
133 - 134      Sweep type:              1 = linear
                                        2 = parabolic
                                        3 = exponential
                                        4 = other
135 - 136      Sweep trace taper length at start, ms.
137 - 138      Sweep trace taper length at end, ms.
139 - 140      Taper type:              1 = linear
                                        2 = cos
                                        3 = other
141 - 142      Alias filter frequency.
143 - 144      Alias filter slope.
145 - 146      Notch filter frequency.
147 - 148      Notch filter slope.
149 - 150      Low cut frequency.
151 - 152      High cut frequency.
153 - 154      Low cut slope.
155 - 156      High cut slope.
157 - 158      Year data recorded.
159 - 160      Day of year.
161 - 162      Hour of day (24 hour clock).
163 - 164      Minute of hour.
165 - 166      Second of minute.
167 - 168      Time basis code:         1 = local
                                        2 = GMT
                                        3 = other
169 - 170      Trace weighting factor - defined as 2-N volts for
               the least significant bit.  (N=0, 1,...,32,767)
171 - 172      Geophone group number of roll switch position one.
173 - 174      Geophone group number of trace number one within
               original field record.
175 - 176      Geophone group number of last trace within
               original field record.
177 - 178      Gape size (total number of groups dropped).
179 - 180      Overtravel associated with taper at beginning or
               end of line:
                                        1 = down (or behind)
                                        2 = up (or ahead)
181 - 240      Unassigned - for optional information.