Seismic Data Format

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

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 (this is the Fish depth below the sea surface in meters*10)

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. UTM Easting coordinate

77 - 80

Source coordinate - Y. UTM Northing coordinate

81 - 84

Group coordinate - X. UTM Easting coordinate

85 - 88

Group coordinate - Y. UTM Northing coordinate

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 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 (four digit integer).

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.

Byte Numbers	Header Value Description
3201 - 3204	Job identification number.
3205 - 3208	Line number.
3209 - 3212	Reel number.
3213 - 3214	Number of data traces per record.
3215 - 3216	Number of auxiliary traces per record.
3217 - 3218	Sample interval, microseconds, this file (reel).
3219 - 3220	Sample interval, microseconds, original field recording.
3221 - 3222	Number of samples per data trace, this file (reel).
3223 - 3224	Number of samples per data trace, original field recording.
3225 - 3226	Data sample format code: 1 = floating point (4 bytes) 2 = fixed point (4 bytes) 3 = fixed point (2 bytes) 4 = fixed point with gain code (4 bytes).
3227 - 3228	CDP fold.
3229 - 3230	Trace sorting code: 1 = as recorded (no) sorting) 2 = CDP ensemble 3 = single fold continuous profile 4 = horizontally stacked
3231 - 3232	Vertical sum code: 1 = no sum 2 = two sum ... N = N sum (N = 32,767)
3233 - 3234	Sweep frequency at start.
3235 - 3236	Sweep frequency at end.
3237 - 3238	Sweep length, ms.
3239 - 3240	Sweep type code: 1 = linear 2 = parabolic 3 = exponential 4 = other
3241 - 3242	Trace number of sweep channel.
3243 - 3244	Sweep trace taper length, ms, at start if tapered.
3245 - 3246	Sweep trace taper length, ms, at end.
3247 - 3248	Taper type: 1 = linear 2 = cos 3 = other
3249 - 3250	Correlated data traces: 1 = no 2 = yes
3251 - 3252	Binary gain recovered: 1 = yes 2 = no
3253 - 3254	Amplitude recovery method: 1 = none 2 = spherical divergence 3 = AGC 4 = other
3255 - 3256	Measurement system: 1 = meters 2 = feet
3257 - 3258	Impulse signal: 1 = Upward = negative number. 2 = Upward = positive number.
3259 - 3260	Vibratory polarity code - seismic signal lags pilot signal by: 1 = 337.5 - 22.5 degrees 2 = 22.5 - 67.5 degrees 3 = 67.5 - 112.5 degrees 4 = 112.5 - 157.5 degrees 5 = 157.5 - 202.5 degrees 6 = 202.5 - 247.5 degrees