segy-js

A library to read SU (and eventually SEG-Y) files and return a JSON formatted array of traces.

Installation

npm install https://github.com/sanandak/segy-js [--save]

Usage

var readSU = require('segy-js').readSU
var su = readSU('filename')

su is a JSON object with 3 fields: ns (number of samples per trace), dt (sample rate in seconds), and traces (an array of traces).

e.g,

su = {ns:750, dt:.004, traces: [trc0, trc1, ...]}

Each member of traces is an object with fields that correspond to the SU/SEGY trace header fields and an array of sample values :

• tracl (trace number in line, at byte 0)
• tracr (trace number in record at byte 4)
• ffid (field file id at byte 8)
• tracf (trace number in file at byte 12)
• ep (energy point id at byte 16)
• cdp (cdp number at byte 20)
• cdpt ?
• offset (source to receiver offset at byte 36)
• sx (source x coordinate at byte 72)
• sy (source y coordinate at byte 76)
• gx (group/receiver coordinate at byte 80)
• gy (group/receiver coordinate at byte 84)
• ns (number of samples in trace at byte 114)
• dt (sample interval at byte 116), converted to seconds
• samps (sample values at byte 240+; assumed floating point big-endian (FIXME); converted to array of objects with sample times and values). See below

e.g,

trc0 = {
     tracl:0,
     tracr: 0,
     ffid:1,
     ...,
     samps:[samp0, samp1, ...]
   }

Each sample value is an object with two fields: t (time in seconds of the sample, relative to the first sample) and v (sample value)

e.g.,

samp0 = {t: 0, v: .01}

TODO

Populate all the trace header fields.

Tests

TBD

Contributing

TBD

Release History

• v0.1.0 Initial Release

Reference

The SEG-Y format is documented at http://seg.org/Publications/SEG-Technical-Standards.

The SU format is similar to SEG-Y Rev. 1, but without the Text and Binary tape reel headers (bytes 0-3600), and with modifications to the trace header fields.

http://www.cwp.mines.edu/cwpcodes/